(Topic ID: 229354)

Meteor Resets – With Rottendog Solenoid Driver Board

By oldschoolbob

1 year ago

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  • 315 posts
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  • Latest reply 1 year ago by oldschoolbob
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Linked Games

  • Meteor Stern Electronics, 1979

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#1 1 year ago

Just over a year ago my friend brought me his Stern Meteor – it was DOA. I rebuilt the rectifier board with new bridge rectifiers and new header pins. I did a lot of work on the MPU including new header pins. Also new headers on the sound board and light driver board. I replaced all the crimp connectors. I rebuilt the flippers, drop targets and pop bumper. I cleaned and re-set all the switches. I didn’t touch the solenoid driver board (except one new transistor) because it was a new Rottendog board. The game played great.

About a year after he picked it up he said it would randomly re-boot in mid-game (usually when he hit the right flippers). I understand this is usually caused by the 5 volts falling too low. I asked him to bring the game back and I would check it out.

First I checked all the voltages. Everything checked OK including 5.7 volts at MPU TP5. I played it for a few days and it was fine – then suddenly the coils went out. I found the problem was a blown fuse under the playfield. I replaced the fuse but couldn’t find what make it blow. I played it for several more days (probably 50 games). It played fine but this evening while I was playing it re-booted mid game. I played a few more games and it was fine again.

My question is; has anyone had problems with Rottendog driver boards. Could the 5 volt regulator (LM1085) be going out or the C10 capacitor (10,000 uF)? Should I replace them with the same or is there something better? I don’t have any of those in my stock pile. But I do have a very nice (and rebuilt) Bally driver board. For some reason I just don’t trust that Rottendog board.



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#3 1 year ago

I checked with GPE and he doesn't have LM1085 voltage regulator - but he does have several regulators. Which one do you recommend?

He also has several 10,000 uF capacitors. I think this is the one I need:




#5 1 year ago

Andrew, you are correct. I checked the voltages again - 4.94 at the MPU and 5.02 at the SDB. Don't know where I got the 5.7. Maybe I was reading the DMM incorrectly.

After being on for only a couple of minutes the regulator heatsink was warn but the regulator was hot. I could touch it but I wouldn't want to leave my finger on it very long.

GPE doesn't have the LM1085 or LM1084. Where is a good place to get them?



#6 1 year ago

This regulator story just gets worse. A while back I picked up a Bally solenoid driver board that looked pretty good. Looks like it has new capacitors and new regulator. I changed the headers and added the ground mods. I thought I'd bench test it before I switched it with the Rottendog. I connected my 12 volt power supply but I only get .78 mV on the TP1. What's strange is the .78 mV keeps going up the longer I hold the DMM on it. After a several seconds it when up to 1.25 mV. I think the regulator is bad or maybe it's installed wrong.

Then I pulled out my old Stern SDB. It still has the original caps. It shows 5.4 volts at TP1 but my 12 volt power supply drops from 12.9 volts to 9.3 volts. Is that normal?

I remember reading some horror stories about counterfeit and junk LM 323 regulators. Where is a good place to get good ones? GPE doesn't have them in stock.


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#7 1 year ago
Quoted from barakandl:

You could use a LM1084 as it is the beefier version of LM1085 but i don't think that is going to fix your issue unless it is going into thermal shutdown and the 5a part holds up better.

That thing does get really hot. I played just a couple of games and even the heatsink was too hot to touch. If you don't think that's the problem what else do you suggest could be causing it?


#11 1 year ago

When I checked the other day I had 5.02 volts at the driver board and 4.94 at the MPU. Could that drop be a bad connector? The connectors and headers are new (a year old) but it wouldn't be the first time I messes up a connector. I think I'll change those connectors to be sure.

It wouldn't be easy to monitor the 5 volts - I played it for 4 days (maybe 50 games) and it only re-booted once.

I'm not a big proponent of after market boards either. I like the original boards (I guess I'm old school). That's why I'm trying to fix the old SDB.

Thanks for the reminder about the diodes. I remember reading that someone fixed their reset problem by replacing the flipper diodes. Cheap and easy repair - I'll give that a try.

I saw those PSU5's on Ebay and was wondering if they would work. When you jumper over the R50, do you just remove it and install a jumper wire or 0 ohm resistor?

I just ordered some of those from Ezsbc. Thanks.


#13 1 year ago

Thanks Ed, I have some bell wire (22 gauge, I think) about the same as a resistor lead.

Do you have any substitute for the LM 1084 or 1085 for the rottendog?

By the way, if you're done painting, you can always come to my house.


1 week later
#14 1 year ago

I got the PSU5's the other day. I also got 2 LM323K's from Jameco. The PSU5's look a little strange - they don't have a cover over the electronics. So I thought I'd try the LM323 first. When I removed the old LM323 it looks just like the Chinese junk the Quench posted a while back. Large blue dielectric and even the same printing on the front. The new one from Jameco looks much better.

After I replaced it, I thought I'd bench test it first. My power supply shows 13 volts with nothing connected. When I connect the driver board it drops down to 10 volts. This also happened when I connected my old Stern board. Is this normal? Is my power supply going bad?



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#16 1 year ago

Thanks Quench, You really got good eyes. The black wire was there before I got it. Looks like the solder pad was lost when he replaced a capacitor and he added the black wire to make the connection. I didn't like it but left it there anyway. It looks close but it's because the solder is mounted high.

My power supply has test chips - ground and 12 volts (actually measures 13 volts). I connect ground to the ground test point and the 12 volts to TP5. Using my multimeter I checked TP3 for 5 volts, then I checked the test clip while still on TP5. It only measured 10 volts. Then I removed the test clip and just measured the test clip (not connected to anything) it then measured 13 volts. 3 volts seems like a big drop with just the driver board connected.

This is an old photo showing my power supply. This is not from last night.



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#18 1 year ago

Yes, I am getting 5 volts at TP3 (actually just over 5 volts - 5.2, 5.4).
There is a regulator on the back of the power supply. I don't know what it is tho.
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A little history on the power supply - I built this power supply from an article I read about 40 years ago. I built it for testing car radios without using a car battery. I pulled it out of storage to use as a 12 volt power source when I started messing with pinball MPU boards. At the time I was using an old solenoid driver board to get the 5 volts. (That's what I'm using in the photo in the previous post above). What you don't see in the photo above is the black, red, and yellow wires (at the bottom of the of the photo) are connected to a MPU.

About 6 months ago I decided to replicate the 5 volt section of a solenoid driver board inside the power supply so I wouldn't need the driver board. Now the power supply has 12 volts and 5 volts.
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When I get back down to the shop I'll hook it up to my oscilloscope and report the findings.



#19 1 year ago

First photo is power supply not connected to anything.

Second photo is power supply connected to solenoid driver board.

I kinda thought the fluctuation would be a lot more. If I'm reading this correctly it's only 160 mV.

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#21 1 year ago

If I leave the power supply hooked up for a while (10 minutes) would the 10 volts go up?

I didn't see any markings on the 12 volt regulator from the photos but I'll check closer with a magnifier.

The two capacitors are in parallel - I remember the article said if you can't find the proper capacitor (I don't recall the size) you could use two in parallel. - strange that I can remember that from 40 years ago.

I thought about re-doing the wiring inside the power supply because it's a mess - not as clean as the 5 volt section. But it works fine - The old saying - if it ain't broke, don't fix it.

#24 1 year ago

Bill, yes I did get side tracked a bit but the power supply issue is important to me. I have used computer power supplies before. When I repaired my first game I used an AT power supply. When I couldn’t get it to boot at the bench I sent it out for repair. He told me it booted right up. He made a few other repairs and sent it back. Even though it was showing 5 volts and 12 volts, I threw out that power supply and got another. Later when I was working on another game I couldn’t get it to boot on the bench with the new AT power supply even after replacing almost everything on the board. Finally I just put it in the game and it worked fine. That’s when I pulled out this old power supply. I have no confidence in computer power supplies.

Getting back to the Rottendog solenoid driver, I did locate a new LM1085 regulator. I haven’t changed it yet because the original regulator is riveted to the heatsink. And I would rather use a Bally / Stern board. I replaced the regulator on this old Bally board but when I tried it out (it booted fine) but it had two transistors bad. – One stuck on and another not firing the coil. I replaced the transistors and tomorrow I’ll try it again.

Thanks for your suggestion and comment.


#25 1 year ago

Quench, you’re right – I left the power supply on for 20 minutes – it went from 10.3 to 10.4. No difference. Tomorrow I’ll check what voltage I’m getting at the rectifier.

It should be easy to add a switch to get 12 volts – unregulated. I guess I could even use the same output jack. Just have a switch for regulated and unregulated. But, when testing MPU’s would I want regulated or unregulated? I know this power supply works great for testing MPU’s and I don’t recall ever showing 10 volts when testing them.

I looked for a name or number on the regulator but didn’t see anything with a magnifying glass.

You worried me when you said those caps may be wired wrong. I had to open it up and check. I’m sure they are correct. But while I had it open I decided to make a sketch of what’s in there. At least if I decide to rebuild it I’ll know what I’m working with. Here’s a photo of my sketch. Not sure if you can read it!

I found that the chassis is connected directly to the positive of the bridge rectifier (I don’t like that at all). I found that the 100 ohm resistor is connected to the end tab of that connector block. Nothing else is connected there except it’s bolted to the chassis. Then I noticed the other end of the connector block has a jumper wire connected to the positive of the rectifier and it’s bolted to the chassis. I checked it with my meter and they are showing continuity. More reason to rebuild this in the near future.

I think I’ll check with GPE for new parts to rebuild this. Any idea what that small red thing is? Diode?



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#28 1 year ago

After I replaced the driver board transistors yesterday, today I installed the board back in the game. It worked great. In test mode I got no stuck-on switches and all the coils worked. As a matter of fact the game seemed to play faster (but that's probably just in my head). I only had time to play a few games so this week I'll play it every day to see if the reset problem is fixed.

Back to the power supply - before I put the board back in the game I connected the power supply back up. Still 10 volts at TP5. Then I checked the bridge rectifier and it showed 14.68 volts. So the board and the regulated power supply don't play well together. This isn't a big issue because I seldom use this to power a solenoid driver board.

What does bother me is the chassis being 12 volt +. Like you said an accident waiting to happen - I could easily drop the negative clip on the box. I must fix this before I reassemble the power supply. I'm thinking I'll re-route the 100 ohm resistor to the + of the rectifier and disconnect the jumpers on the connector block. Then isolate the regulator (TO-3 transistor) and add a wire from the collector case to the + rectifier. Sounds easy on paper.

I thought a zener diode would be easy. I checked with GPE and he has 4 pages of zener diodes. So far I can't see the markings. I may have to remove it to see.



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#29 1 year ago

I think I found the number on the zener diode. It looks to me like 1N4744. It also looks like it may be cracked. The only part left unknown is the regulator / transistor. I dug around in my old parts drawer and found one with the same blue paint as the one in the power supply. I was hoping it had a number somewhere but it didn’t.

I’m thinking very seriously about building a new power supply over the holidays for several reasons. The inside looks like a rats nest. Looking at the rectifier leads, I may have used acid core solder back then. Also I have a 24 volt power supply I sometimes use for testing zero crossing – I think I’d like to have it in the same case. And it would be neat to have volt – amp meters in the front panel. Not really necessary but it would look cool. And the last reason, I need something to do over the holidays.

The old unit has two 1000 ohm capacitors. I’d like to replace those with one cap. GPE doesn’t have a 2000 ohm but he does have 2200. Would that work the same?



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#30 1 year ago

In order to eliminate the 12 volts going into the chassis

Quoted from oldschoolbob:

I'm thinking I'll re-route the 100 ohm resistor to the + of the rectifier and disconnect the jumpers on the connector block. Then isolate the regulator (TO-3 transistor) and add a wire from the collector case to the + rectifier. Sounds easy on paper.

This is what I think the revised sketch will look like. Will this work or blow something up?

When I checked continuity the rectifier, The TO-3 case and the 100 ohm all showed continuity. And so did the chassis too.



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#32 1 year ago

First of all, thank you for the schematic. I was working on one last night but it's not near as neat as your's.

I think I have some transistor gaskets and spacers but I seldom use them because it seems they would restrict heat transfer to the heatsink. I was planing to remount the heatsink with plastic washers to isolate it from the case.

As soon as I get to the shop I'll connect the oscilloscope and report back.



#33 1 year ago

I thought you might need a good laugh today. My Schematic:
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Here's how I isolated the 5 volt regulator and heatsink. I don't know why I isolated it when I added it 6 months ago but I'm glad I did knowing now that the case is 12+. Just lucky I guess.
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The scope shows 17 volts.DC at the rectifier. Seems high. So I checked the AC at the rectifier. It shows 22.8 volts. The label on the transformer says 12.6 volts. These numbers all seem high so I checked with my meter. It shows 13.7 at the AC rectifier and 17.31 DC at the rectifier. These numbers seems way off to me.

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#34 1 year ago

This Meteor game is haunted. At the end of the first ball, first game it started counting down the bonus points but just kept counting and counting. I immediately hit the test switch to check for a stuck on switch. It showed "0". I turned it off then back on. I played several more games and everything was fine. I hate when that happens. Can't fix it when it ain't broke.

#36 1 year ago

Thanks Tom, that's very, very interesting. Mine was doing the same thing except it was counting on rocket 3.

I've never seen that before and I've worked on two different Meteor games. Hopefully I'll never see it again.

I've bookmarked this for future reference.



#38 1 year ago

Here’s the way I understand RMS. This is a wave form (or half of a wave form):
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If we could fill that up with water, we’d have a certain volume of water in there:

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If we could compress that water till the ends are square, the wave form would look like this:
wave 3 (resized).jpg

This would be the RMS.

I must be reading the oscilloscope numbers wrong. You said the peaks reach +17 to -17 for 34 volts peak to peak. Looking at the numbers on the bottom – the bottom left number shows 10.0V. I thought that was 10.0 volts per division. If you count the horizontal divisions it would be over 30 volts. If you look at the yellow bar at the bottom it shows Pk – Pk 66.8V. And RMS 22.8V. However, your numbers closely match what I’m reading on my DMM.

Sometimes I think the more I learn the less I know. But I do appreciate you taking the time to teach me. I hope there are others following this and they are getting something out of all this too.

#40 1 year ago
Quoted from Quench:

I think you've discovered a bug in that Hantek software.

I just remembered - my probe may be set on 10X. That would give me some messed up numbers. I'll check when I get to the shop.


#41 1 year ago

It was set on 10X. I'll re-scope as soon as I get it re-assembled.


#42 1 year ago

I got it back together. No more 12 volts on the chassis now. I feel better. Using my multimeter - 5.33 DC at the output - 12.9 DC at the output - 13.1 AC at the rectifier. All looks good.

When you said "If you count the divisions as 5 volts each, the readings make sense" it made me think about the 10X probe setting. So I changed the probe to 1X and re-scoped. Your previous post about +17 volts and -17 volts was spot on. I wonder why the probe setting didn't seem to effect the DC reading?
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I used your schematic and added in the 5 volt section from a solenoid driver board schematic. (that's what I did before). I know you're busy but when you have time could you please look this over and make any changes or suggestions.
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Also, if anyone is following this please add any suggestions or comments. I appreciate all input.

And if anyone is following - second day of playing Meteor with the Bally SDB and it's still working fine - hasn't re-set once. I'll keep playing to see if we got it fixed.



#44 1 year ago

For those brave souls still following the Meteor problem. Looks like the problem wasn't the driver board. I played a bunch of games yesterday and a dozen games today. I was thinking I had it fixed. Tonight I thought I'd try a few more games. About the third game the S-O-B rebooted. And I think it happened when I hit the right flipper. Looks like I still got some work to do. Next I'll try new flipper diodes then new connectors from the driver board to the MPU.

Stay tuned for the next Meteor episode.


#45 1 year ago
Quoted from Quench:

Connect the input of the LM323 to the unregulated output of the rectifier.

Please look at the revised schematic to see if I understand this correctly.
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You’re saying I only need one 15,000uF capacitor? (the 5 volt cap I installed is a 15,000) Where would it go – at the C1 or C23?

I’ve seen that datasheet information before (I think it’s on the driver board schematic). The way I understand it is if the regulator is more than 4 inches away you must install the small capacitors. That’s why they’re on the driver board and I added them here. (and on the existing 5 volt section I added). However, this brings up another potential problem. I was planning on attaching the regulator and transistor on heatsinks similar to what I have now except I was going to go through Molex headers and connectors to make the new PC board removable. Maybe that’s not a good idea.

I didn’t want to take up a bunch of space here so I made a picture album of this power supply showing what I have at this point. I tried to get every angle possible.


On the 10X probe, I should have mentioned that I not only changed the probe to 1X, I also changed the probe attenuation in the channel one menu to 1X. I don’t recall what it was before but it wasn’t 1X. This oscilloscope has more menus and setting than I know how to deal with. Maybe someday I’ll learn.
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I haven’t done anything about the scoring bug. Changing ROM’s means I’d have to order new ones (don’t have a burner) and I’d probably have to change jumpers also. If it continues to be a problem then I’ll check into it.



#47 1 year ago

I think I made it public now. Try again.

Or try this link:


#48 1 year ago
Quoted from Quench:

C1 and C23 are on the same circuit now, so you're pretty much putting the cap on the rail.

So it doesn't matter if the cap is before or after the Q1?

That changes my concept of this whole electronics thing. This is so interesting.



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#53 1 year ago

This my latest schematic (don't laugh - it took me all day to do this). But I see from Quench's post that I must move C23v to the left of R1. I'll get back to the other comments shortly.



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#57 1 year ago

Mark, thanks for stopping in. Can never have enough comments or teachers. And just because I have a scope doesn’t mean I know what I’m doing. Fortunately I didn’t have to pass a test to buy it. I’m 72 with no experience in electronics (career in construction) but I always liked electronics. Yes, Quench has always given great advice and he’s an excellent teacher. He explains things in simple terms that even I can understand.

A quick history – I built the original 12 volt power supply 40 years ago. Six months ago I added in the 5 volt section (copied from a Bally driver board) for testing MPUs. It’s worked great and I don’t want to deviate too much from this design. The main reason for building a new one is because it’s a rats nest inside. What I’m thinking is to rebuild everything I have on a single PC board to clean it up.

And before anyone suggests it would be easier (and probably cheaper) just to buy a power supply – I agree, but what’s the fun in that.

Thanks for the link to LTSpice. That’s sounds like something I’ll enjoy and maybe learn something. I’ll try it later tonight.

Quench, here’s my latest version with the 15,000 cap moved before the Q1.

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Quoted from Quench:

I would move the input section of the 5V regulator/components circuit to the output of the rectifier so the two regulator circuits are somewhat independent other than the bridge and C23. Just like you had it earlier.

Well, back to the drawing board – no problem. Maybe I’ll apply for a job as an electronics engineer when I get this done. NOT.

By the way does the photo album work now?


#58 1 year ago

Mark, that reminds me, Quench suggested I install fuses (probably a good idea) but I didn't know for sure where or what size. I'm guessing 3 amp fuses at the output side.

The existing transformer is 12.6 volts - 3 amp. The replacement I'm looking at is 12V - 4 A.

The transistor and regulator are mounted on heatsinks. I usually only use this for testing pinball boards and the heatsinks don't even get warm. However, I have used this for testing 12 volt 55 watt halogen bulbs before. That's over 4 amps and it worked OK.


#60 1 year ago

Back before I added the 5 volt section I was using the 12 volt (regulated) supply to power a driver board - then connect the driver board to the MPU. (As shown back in post 16.) This worked really well but was a bit of a hassle to connect everything. So when I added the 5 volt section I wanted to replicate the same thing. That's why I'm leery of changing too much in this new design. After I added the 5 volt section it works great.

The first photo shows a red wire connected to the 12 volt output post and then to the 15,000 cap. (just like the Bally/Stern schematic) This is then connected to the PC board. If you look closely at the next photo you can see some green lines drawn on the PC board. This is where I cut away the copper cladding on the other side. (I didn't have any etchant). All the 5 volt components are on the PC board.

Having the 5 volt from the 12 volt regulated didn't seem to have any adverse effect when I used the driver board or with this new 5 volt addition.

This thing works so well I'm a little reluctant to make many changes. I don't even mind keeping the two 1000uF caps (but a single 2000 would look better). 2000uF caps seem to be difficult to find but GPE has 2200uf. Would that work as well?



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#61 1 year ago

Here is my latest schematic. I’m pretty sure this is exactly what I’m using now. Except I omitted the diode on the 12 volt + and added the fuses. Everyone, please look this over and let me know your comments, questions, and suggestions. I really would appreciate it.

I need to get my parts ordered this week because GPE is closing down till next year.



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#64 1 year ago

Mark, thanks for the great advise.

The fuse before the rectifier is a great idea. How many times have we added fuses to Williams system 6 games before the rectifiers. (same thing). The new supply will have a new transformer – 12 volts 4 amps. I think a 3 amp fuse should work well here. I think I’ll leave in the 3 amp fuses on the output – can’t hurt. The old supply does have a 120 volt fuse in the back of the case. I was planning to install one on the new supply as well.

I thought the C24 cap was there because the regulator may be more than 4 inches from the filter capacitor. (See the datasheet info on Quench’s post 43). Also Bally/Stern has that cap on their driver boards.

The current draw on the 5 volt side shouldn’t be much. The only time I’ve used the 5 volts was to test MPU boards.

I just purchased a bunch of tubes of thermal grease. I always use it when installing heatsinks on rectifiers but for some reason I haven’t been using it for regulators. I guess I forgot. (And that stuff is messy.) I’ll remember to use it on the new supply.

That’s a great looking power supply. If mine was that nice inside I probably wouldn’t be rebuilding. I see you have 12 volts fixed and variable. Can you output 12 volts and 5 volts at the same time? Also where did you get the lettering on the front panel? Looks very professional.



#65 1 year ago

Using the schematic in post 61, I started drawing the PC board layout when I noticed something. Looks to me like (electrically) point A and point B are the same. Point C and D are the same. And so are E and F.

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To simplify the PC board layout I when back to change the schematic as shown below. When I was done I noticed the new schematic looks very similar to the one in post 57 - except the location of C1, C1a, and C23.

R7 12 and 5 volt power supply r7 (resized).jpg

Re-reading the posts, Quench suggested moving the input of the 5 volt section to the rectifier. As shown in blue marked up. But this isn’t how the old supply is built. The 5 volt section comes right off the 12 volt regulated output. I guess I could build it this way and if it don’t work, I could scrape off some copper cladding and add some jumper wires as shown in blue.

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This sounded simple when I started but now I’m giving everyone a headache. I gotta get some rest.


#68 1 year ago
Quoted from Quench:

You've accidentally moved that F1 fuse from the 12V rail to ground. It must go back on the 12V rail.

Just proves I shouldn't do this late at night.

I have these in my cart on Ebay.

ebay.com link » Digital Red Led Voltage Meter Dc 100v 10a Voltmeter Ammeter Blue Red Led Dual



#80 1 year ago

WOW! I didn't know adding a couple of meters would be so complicated. I just thought I could get a couple of meters and stick them in there to look professional. They really aren't necessary. I never looked at the wiring diagrams. I saw them on Amazon first and thought they would look cool. Then I found them on Ebay much cheaper. Are they both the same? Is there another meter you would suggest that's easy to install? Maybe I should just use a couple of volt meters.

I have a couple of old analog meters around but I like the digital.

Mark, thanks for the updated schematic (shows what can be done in a few minutes when you know what you're doing). I had the 15,000 cap on the 5 volt side because that's about what I have now. I'm not sure about the 2K resistor - there's not one there now but it works.

Thanks for the lessons guys.


#81 1 year ago

If I were to use my DMM to check amps, I would just cut into the + wire and put in my meter.

Why wouldn't this meter work the same way?

What's the purpose for the shunt?


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#83 1 year ago

Glad your here Mike. Hope you learn something as I have. If you have any questions or comments just put them out there. These are great guys and they will be able to answer your questions.

I looked over the photos on the Ebay meter and they show this with no external shunt. Looks like is has a built in shunt. So what would be the problem hooking two meters up to to different voltages on the same negative side? See photos below. We have a common ground on the power supply board anyway.

V A meter 1a (resized).jpgV A meter (resized).jpgV A meter x2 (resized).jpg

#85 1 year ago

I said "If I were to use my DMM to check amps, I would just cut into the + wire and put in my meter." you answered "yes". Why can't we do that here?

The way I understand the shunt it's a very small resistor the makes about 10% of the current go through the meter.

Quoted from Quench:

Nothing wrong with hooking up two analog current meters on the plus side.

Wouldn't the digital meter work the same?

It's 6:30 AM here - I gotta get some rest.

I'll think about this in bed.



#89 1 year ago

Pinengineer, the display on that is awesome, more stuff on there than I'd know what to do with. And I like the simplicity - two wires in and two wires out. But it's big (about 2 inches X 3 inches). And it's adjustable - I can see me screwing something up by connecting it before I have it adjusted. Just connecting fixed 12 volts and 5 volts to the correct test points is dangerous for me.

I'm beginning to think this amp meter thing is getting too complicated. It would look neat but I don't think I really need it (or would even use it). I'm thinking now about just a couple of volt meters would do the trick. Something like these:

ebay.com link » Red Mini Voltmeter Dc 5v To 120v 3 Digital Display Voltage Volt Meter Led Panel

ebay.com link » 3pcs Dc 0 30v Red Led 3 Digital Display Voltage Meter Voltmeter Panel Motorcycle

ebay.com link » 1x Mini Red Blue Green Led Dc 0 100v Voltmeter Gauge Voltage Volt Panel Meter Us

Something just occurred to me - I always install a pilot light to indicate that the unit is on. Adding the meters would eliminate the need for a light.

Today I'm working on my PCB layout. We'll see how that goes.



#92 1 year ago

I haven't bought anything yet but everything is in shopping carts (4 vendors). Quench, I'm leaning toward the second meter - nice size, good price (3 for 9.99) and they're in the states.

Everything is in carts except for the Q1. I don't know what it is. There's no markings on it. I found one in my old parts drawer that I'm 90 percent sure it's the same. It has the same blue paint as the old one. Is there anyway to verify that they are the same?



IMG_2883 (resized).JPGIMG_2887 (resized).JPG
#100 1 year ago

Mark, I appreciate the time you spend here. I know how valuable time is for a working man with family. (been there).

I saw that current clamp when I got my scope (it’s also Hantek). I figured I didn’t need it. Years ago I had a handheld clamp meter – I lost it somewhere but I never missed it.

I decided the best solution for the amp meter is not to use one on here. I don’t think I really need it anyway (they just looked cool). I will install a couple of volt meters – should look just as cool.

On the addition of the 2K resistor. Quench said a while back that he sometimes has problems with his computer power supply (something about the VR1 being out of spec) If he manually resets the MPU it will start up fine. I’ve never had that problem with this supply. Maybe (just maybe) it’s because my 12 volt is not fully energized until it sees a load. I really don’t know, but maybe Quench or someone could give an explanation. For this reason, I’m a little reluctant to add it at this time.

By the way, how was the date with your wife. Did you guys have a good time?



#105 1 year ago

My original idea was to build an exact copy of this power supply and leave this one alone. But I'm beginning to realize that's not possible. The Q1 transistor is unknown and Quench just indicated if I change the transformer I'll need to change the zener and resistor. So I decided to reuse the transistor and transformer from the old unit. Once we get the new one working I can go back and mess with the old unit.

This is my first PC board layout. I'm already working on the second version because this is a bit big. One of the problem areas is the two 1000uF caps. I found a 2000uF cap at Mouser but the deal breaker is 8.00 shipping for a 2.00 part. GPE has 2200uF in stock. Will one of those work?



pcb layout 06 (resized).jpg
#108 1 year ago

Mark, thanks for the lead on Arrow. I've never ordered from there before. They have 2000 uF caps. I just ordered a bunch of caps from them.

By changing the two 1000 uF caps for a single 2000 uF I was able to reduce the size of my PC board to 4 x 6. Much better now.


pcb layout 08 (resized).jpg
#113 1 year ago

The main reason I buy from Ed is I know I’m getting top quality parts at a reasonable price. When I’m forced to buy from other suppliers I’m always concerned about the quality of what I’m getting. Also Ed’s shipping has always been reasonable. And the parts are nicely packed and well marked.

Ed, the reason for the rather odd location of the capacitors is I’m trying to replicate my old power supply. It started 40 years ago as a 12 power supply to run auto radios without a battery. Six months ago I added the 5 volt section copied from a Bally solenoid driver board. It’s worked very well for testing MPU’s. The original transistor (Q1) is unknown – no markings.

I hate to change the design but now I’m thinking maybe I should change. The problem is I must get my order into GPE tomorrow before he closes for the year.

I got a real problem now.


#114 1 year ago

Maybe my problem isn't too big. Everyone (and I do mean EVERYONE) has told me to remove the 2000uF and to move the 15,000 to it's place. Would that change make any difference to any of the other components?

Maybe I shouldn't be so bullheaded especially when I don't know what I'm doing.

Here is the latest board layout. Please, everyone, look this over - I'm ordering parts tomorrow.



pcb layout 09 (resized).jpg
#116 1 year ago
Quoted from Quench:

I'm not so sure it's worked that well

I chuckled when I read that. You're right - a month ago I was happy with my power supply. But look at what I've learned and all I will learn if I ever get it built. Besides that, it'll give me something to do.

Here's my parts list from GPE. Plus I got parts from Amazon (case and stuff), Jameco (PC boards, rectifiers, etc.), Arrow (more capacitors), and meters from Ebay. The first few items are for other projects or parts drawer.

It'll be a fun project.



parts 1 (resized).PNGparts 2 (resized).PNG
#117 1 year ago


I added the 2K resistor to the layout. Is this where it should be installed?

What size (watts) should it be?



pcb layout 11 (resized).jpg
#120 1 year ago
Quoted from Quench:

The 2k resistor connects between common and the emitter of Q1, basically across the 12V output.

I think that's what I have - the black lines crossing (just left of F1) are all the same continuity.

Quoted from Quench:

BTW, check the connections on your Q1 transistor above. The line going up from ZD1 should go to the base, not the emitter. And the base shouldn't be connected to the collector.

Wow, did I screw up there. I think C2 is also suppose to connect to "B". And R1 connects between "B" and the + of the rectifier. I gotta re-do that whole area - what was I thinking?

Quoted from Quench:

Skip the 13V 1/2W zener, 1/2W sees too low. Get a 13V 5W zener instead.

Out of 4 pages of zeners GPE don't list a 13V 5W. Only 1 watt and 1/2 watt. Those zeners are pretty cheap. Can you recommend a list of them that I "might" need for this project? I'd hate to have this project stall because of some zener I don't have.

I just added some 2K 1/2 watt resistors to the list.

Thanks guys


#121 1 year ago

Thanks again for finding that mess up on the Q1. That would have been a disaster.

Here's the latest layout.

Any ideas on the zeners?



pcb layout 12a (resized).jpg
#122 1 year ago
pcb layout 14a (resized).jpg
#124 1 year ago

Do you think we could find a new transistor that fits this situation without changing too much of everything?

#125 1 year ago

GPE doesn't have that number - but Arrow has 1N5350BG and 1N5350BRLG. I ordered 2 of each.

#127 1 year ago

Update - all the parts are ordered (5 vendors) and shipped. Hopefully things will be rolling in this week.

In the meantime I'm back on the Meteor. I removed the bottom right flipper coil to replace the diodes. Once on the bench I noticed the coil sleeve was stuck. Usually a sign that the coil got hot. I checked it with an ohm meter but it checked OK. Is it possible that the coil gets hot, the windings expand and cause a short that resets the game. Then the coil cools and the windings contract and the short goes away?

I found a matching coil in my parts box and replaced it. It works now but I only played a couple of games. We'll see if that fixes it.



#128 1 year ago

I been playing the Meteor everyday for the past 2 days and so far so good - time will tell.

All power supply parts are here except GPE. Looks like USPS shipped it 100 miles past my house today. Maybe tomorrow.

One of the parts that arrived is the new transformer. Seems that someone suggested I reuse the old transformer but I can't find the post. I'd rather use the new one than mess with removing the old one. The old one is 12.6 volts - 3 amps. The new one is 12 volts - 4 amps. I measured both today. The old one measures 13.1 volts and the new one is 12.1 volts. Would it hurt anything to just use the new transformer?



#130 1 year ago
Quoted from Quench:

At 12.1V on the new transformer, the transistor (and 5V regulator depending where you wire it) will dissipate a little less heat

That's a good thing right?

0.602 volts between B & E.


#132 1 year ago

The only load is the 5 volt section. Nothing connected to the outputs.

I cleaned it with a brush. I even looked on the edges of the case. No markings. I looked over it's cousin with the same blue paint and no marking on that either. Who would make a part and not have any markings.

#133 1 year ago

I'm not a big fan of headers and connectors but looking at the layout of my power supply, installing or replacing the transistor and regulator is not going to be easy. They'll be hardwired to the PC board. I could add headers to the PC board and use connectors wired to the transistor and regulator. But this adds a point of failure.

If you were building this would you use headers and connectors?



box 02 low voltage (resized).png16513 (resized).jpg
#135 1 year ago

Thanks Ed, I've never seen those before. If you use them all the time - I'm sold. They should work for the other PC board connectors also. I just ordered two dozen. The only down side is they take up a lot of space but I should be OK.



#138 1 year ago

I thought about having the board made but I only need one. (if I get it right the first time). But I bought three boards just in case.

I plan to make the traces as large as possible. Not only makes it heavy duty but also less copper to etch off. I made a couple of PC boards but that was years ago. I’m sure I’ll have questions as I go. I was going to layout the components, drill the holes, then mark out the traces with a magic marker and sharpie. Then dip it in etchant. I got some powdered stuff that makes a pint of ferric chloride.

This is only a single sided board. Trying to keep it simple so no vias. Maybe my next project will be more complicated.

I still don’t have parts from GPE. GPE is only 400 miles to the west so I usually get my stuff in a couple of days. This time USPS shipped my stuff 150 miles to the east – then sit on it for a day. Then it went to St. Louis (30 miles to the west again). I understand my order is now at the local post office. If they don’t lose it in the next 5 miles I should get them Monday.

In the meantime I been working on the case. The bottom of the case has a bunch of nubs to mount stuff. But my transformers don’t fit the nubs. So I made a plastic mounting plate for the transformers and will attach it to the nubs. The back panel is done. I had to modify the heatsinks to get space for the line fuse and line cord. I started laying out the PC board but I really would like to have the actual parts in hand.

Also I been playing the Meteor. So far it hasn’t reset but I’ve seen that before. I’m not much of a pinball player and I’d rather be working on my projects.


IMG_2933 (resized).JPGIMG_2939 (resized).JPGIMG_2937 (resized).JPG
#139 1 year ago

Today I remembered I have one of these transistor testers.

amazon.com link »

Is there anyway to test a TO-3 transistor with this? Maybe we can find out what the unknown transistor is.



#142 1 year ago

This might help identify what we got. Does it make a difference which way the B and E are connected? I'm guessing the white clip is connected to the E.

Also can it be in circuit?



#143 1 year ago

Mark, the last board I made (for the 5 volt section) I just used a dremel tool to sand away the copper. Crude but it worked.

IMG_2916 (resized).JPG

Here’s a photo of my PC board so far. The big squares are the connector blocks that Ed suggested. They take up a lot of space but should make removing the board easier. I had enough room on the right side to add in the 24 volt rectifier for the zero crossing. The minimum size of the traces should be about 3/16 inch.

IMG_2959b (resized).jpg
#145 1 year ago

I gotta take it out sooner or later - may as well do it now and get over with. I'll take it out tomorrow and report my findings.

I have a hunch that its cousin (with the same blue paint from my parts box) will be a match. I'll test it tomorrow too.



#148 1 year ago

First I hooked up the mystery transistor from the old parts box. Don't seem to be much info here. I have no idea what this is.
IMG_2962 (resized).JPG
IMG_2963 (resized).JPG
Then I removed the transistor from the power supply. Definitely not the same part. I looked this up and it seems to be bipolar NPN. Other than that I'm clueless.
IMG_2967 (resized).JPG
IMG_2969 (resized).JPG
Is this a part that is available today?

Hope someone can shed some light on this.



#151 1 year ago
Quoted from Quench:

But the low current gain is telling us it's not a good choice in this circuit.

This might be a clue. Today I got the volt/amp meters. Before I removed the transistor I thought I'd try it out. I hooked it up and the meter read 12.1 volts. The only thing I had handy to try a load was an old DC motor about an inch long (similar to a slot car motor). The voltage went down and the amps read 0.88. Then it went dark. I turned off the power supply and checked my connections. It didn't blow up the meter so I tried it again - same results. Then I tried one of the "volts only" meters. It went dark also. I just thought the meters didn't like the motor. So I proceeded to remove the transistor. From what you're saying maybe the meters are OK and the power supply is shutting down.

If this is not a good choice what would be a good choice? - Without changing everything.



#152 1 year ago

Mark, EEVBLOG did a review on similar tester some time back. I think he was pretty impressed. After testing the transistor today I thought I'd test some other T0-3 stuff I got in my parts box. The first one was some kind of voltage regulator. The next one gave me something like the first one shown above. Then I tried a LM323K. The tester said bad or unknown part. This worried me because the LM323 is brand new. Then I tried a PSU5 (also new) and got the same bad or unknown part. That's the first time I saw that description but I guess not everything is in it's database. All in all it's a neat little tool.


#154 1 year ago

Last night I was searching for linear power supply schematics and I found this:

12 v schematic (resized).PNG
Also found that Jameco has a 7812K in TO-3 case.


Would this work?



#156 1 year ago

Sorry Mark, next time hit me in the head with a hammer to get my attention. Seriously, I've read this entire thread about a dozen times. When I looked up the LM137 I thought it was a TO-220 and that you were referring to the 5 volt section.

I know I have the 0.1 uF caps - not sure about the 1 uF - I'd have to check. I know I don't have the 7812K.

In my case would I change the 4700uF for a 15,000 uF?

I haven't etched the board yet so I think these changes would be fairly easy.



#158 1 year ago

A couple of things I just noticed - the schematic about shows 14 - 35 volt transformer. I only have a 12 volt.

The 1 uF cap - what kind should it be? Electrolytic?



#159 1 year ago

Thanks Quench.

Do I really need more than 1.5 amps for pinball testing? How many amps do you think my old supply was putting out? I'd guess less than 1.


Here's the changes to the board layout:

pcb layout 15 (resized).jpg
#161 1 year ago

I had to order the 7812 so I also got a 24 volt transformer.

I got the board laid out and the holes drilled. This looks way to simple. I must be missing something.



IMG_2987a (resized).jpg
#163 1 year ago

I checked Jameco yesterday for a 18 volt transformer - all they showed was a few wall-warts in 18 volts. So I ordered the 24 volt. Today I checked Ebay for 18 volt transformers and found 18V 1A and 18V 2A. Both sold by JAMECO!!!. That pissed me off. If their website would have had the 18 volt transformers listed I would have got one instead of the 24.

Do you think the 24 volt will have to dissipate too much heat?



#165 1 year ago

This is the regulator I ordered. There is a data sheet attached but I don't understand 90% of it!


My old transformer measured 13.1 volts AC at the bridge rectifier.

The new 12 volt transformer measures 12.1 VAC. (not connected).

I haven't received the 24 volt transformer yet. But this is what I ordered:




#167 1 year ago

Thanks for the links Mark. I bookmarked them. I always need something to read late at night when I can't sleep.

I etched the board today. It looks almost as good as those boards you buy commercially. Don't you agree?


IMG_2994 (resized).JPG
#169 1 year ago

I've ordered the 7812K and a 24 volt transformer but they won't be here til next Friday. I can change either one easily - I just hope I don't need to change anything on the board. I have all the board components so I'll be assembling it next.


#170 1 year ago

After I made the PCB (above) - I decided to make another little one to clean up the rats nest in the old power supply.
IMG_2998 (resized).JPG
The only part I reused was the rectifier and the transistor. I replaced the two 1000 uF caps with one 2000. I changed to 100 ohm 10 watt resistor for a 100 ohm 5 watt. I replaced the 47 uF with a new one - same size. The only big difference was I replaced the zener with a 1N5350 (13 Volt - 5 Watt). It looks so much better now.
IMG_3007 (resized).JPG
Before I took the old one apart I connected it to my oscilloscope and did some screen saves. The 5 volt is exactly the same.
old 5 volt (resized).jpg
But I went from 13 volts down to 11.8 volts. I lost over 1 volt. Would the zener cause this?
I did notice after I was done that I left the diode on the transistor output. Quench told me to remove it. I'll do that next.
old 12 volt (resized).jpg
new 12 volt (resized).jpg


#171 1 year ago

That did the trick - removed the diode - got 12.6 volts now. I even tried to boot an old MPU and it boots fine.

Can't wait to get the new one together.

Thanks guys


new 12 volt 3 (resized).jpg
#174 1 year ago

Wow, big difference from what I got. And I think I gave more than 20.00 for mine. I really like the test probes.


#175 1 year ago
Quoted from mbwalker:

So give it a test drive with a load next.

First I connected a bulb that showed 0.22 amps - voltage went down to 11.8 and still smooth.

Then I connected a bulb that showed 2.2 amps - voltage dropped to 3 but still smooth.

I couldn't find anything in between to test.

Also got the PC board as far as I could - missing a 1 uF cap (on order). In the meantime I'll work on the front panel.

I hope by this time next week I'll be testing the new power supply.


pic_48_1 (resized).jpgpic_48_2 (resized).jpgIMG_3015 (resized).JPGIMG_3019 (resized).JPG
#179 1 year ago

I'll get to those measurements tonight or tomorrow.

Merry Christmas.


#180 1 year ago

Got in a little shop time tonight.

First tested with the small bulb:

B = 12.62
E = 11.98
C = 15.68

Then tested with the halogen bulb:

B = 5.75
E = 4.96
C = 10.5

What's really strange is E is the output - right? It goes to the output terminal on the front of the case. When I tested at the bulb I got 3 volts. I got 5 volts at the output terminal and at E. I seem to be loosing 2 volts between the output terminal and the bulb. The connector wire is about 36 inches long with an alligator clip on the end. I don't think the wire is undersized.

Hope this makes sense.



#183 1 year ago

I'm sure the halogen bulb is overloading, that's why I tested with small bulb also. The halogen just barely glows. I thought you wanted to to see what a big load would do. I think the halogen is 12 volt - 55 watts. That's about 5 amps.

Do yesterdays numbers above look OK?

I checked the voltage with no load today and had no drop in voltage between the output terminal and the alligator clip. Then I took one of the connector wires off and checked it. It showed about 1 ohm resistance in about 36 inches. I purchased some new test leads for the new power supply and they also showed about 1 ohm.

I cut out the front panel yesterday and painted it last night. I'm trying to put on some rub-on lettering. That's not easy!



box front 1a (resized).png
#185 1 year ago

The resistor is 100 Ω - 5 watt.

Somewhere I have a car taillight bulb that I use for testing in cars but I couldn't find it - that should work better. I'll see what I can find.

About the only time I use the 5 volt is for testing MPU's. I tested one the other day and it worked fine.



#187 1 year ago

Today I received the regulator and 24 volt transformer. I hooked up the regulator to complete the 12 volt section of the new power supply. I had the old 12 volt transformer still installed so I tested with that first. I got 12.1 AC before the rectifier and 11.96 DC at the output. Then I hooked up the 24 volt transformer - 26.2 AC and 11.96 DC. I left it connected with a small load (0.22 amp bulb) and checked the regulator to see if it got hot. After about 10 minutes it was barely warm.

Then I scanned the output with both transformers with the oscilloscope. They were both the same.

I found my old taillight bulb tester. It's just a single filament bulb with jumper wires attached. (look at the bottom right corner of the photo). When I touched it to the output the voltage dropped to 0. Thinking my old taillight bulb was bad, I tested it on the old power supply. It lit fine and showed 1.66 amps. The new power supply seems to work at 0.22 amps but not at 1.66 amps.

I'm a little unhappy that it only goes to 11.96 DC and not 12. I know it's close but I wanted to see 12 volts.

Also with the 12 volt transformer showing the same as the 24 volt, would you change to the 24 volt transformer?

I'm building this power supply for the main purpose of testing MPU's. Would you change anything?

Tomorrow I'll connect the 5 volt regulator and do more testing.



IMG_3041 (resized).JPGpic_49_1 (resized).jpgpic_50_1 (resized).jpg
#189 1 year ago

I remember you telling me that it was limited to 1.5 amps and I read that in some data sheet. I don't think that will be a problem for testing MPU boards.

What I'm most concerned about is the 11.96 volts. If the 11.96 volts hold through the 1.5 amps I'll be in good shape. The MPU's require 11.9 volts at TP2. I'm worried that if the power supply falls below 11.9 it may not work.

Would changing the transformer make any difference?

I looked over the schematic above and making that change would be possible. I'd have to cut a couple of traces, add some components and change some components but it is doable. We'll see what happens when I complete the 5 volt section and give it a test.



#191 1 year ago
Quoted from Quench:

Add two resistors to the 7812 regulator just like the 7805 circuit to bump up the output voltage. Something like a 1k ohm resistor (0.5 watt) between leg 2 (output) and leg 3 (case) of the 7812, and cut the trace from 7812 case to ground and insert an 200 ohm resistor across the cut should bump the output voltage to around 14.35 volts.
If you don't want to go as high as 14.35 volts output, adjust the value of the 200 ohm resistor to something lower.

I think I'll try that. What about the transformer?

I just connected the 5 volt section and connected it to a MPU. It booted !!!. We made something and it works. I'm just thrilled.



#193 1 year ago

First scan is regulator input - 14.6 volts

Second scan is output - 12 volts.

How can I get 14.6 volts from a 12 volt transformer?

This was connected the same as in post 187 with the 0.22 lamp.



pic_51_1 (resized).jpgpic_51_2 (resized).jpg
#194 1 year ago

Additional info.:

I did check TP2 in a game (Meteor) - it read 13.79 volts.

When I booted an old MPU-100 I got 5.29 volts at the power supply and at the MPU.

I got 11.93 at the power supply and 11.86 at the MPU.

I need to pull the power supply board to change the wires to the 15,000 uF cap. I cut them too short. I think I'll add the resistors you suggested if I have the right sizes in stock. I'd like to see about 13 to 13.5 volts if possible.



#196 1 year ago

I don't have more 0.22 amp bulbs but I might have some other 12 volt car bulbs in the garage. I need a 1 amp bulb. I'll check.

Quoted from Quench:

If you don't want to go as high as 14.35 volts output, adjust the value of the 200 ohm resistor to something lower.

I found a 100 ohm resistor. Would that get me close to 13 volts?

I also found a 1K ohm that I think is 1/2 watt. And I have a monster 1K ohm.

If I change the 12 volt transformer to 24 volt do you think I'll have a heat dissipation problem? I'm very tempted to leave it as it is. It works for what I wanted (testing MPU's). And I still have my old power supply that puts out 12.3 volts.

What would you do?



IMG_3044 (resized).JPG
#198 1 year ago

I found another car bulb in the garage - It shows 0.53 amps. I hooked it up to the new power supply and the voltage is still 11.9. I'm happy with that. I know it will output over 0.5 amps and hold 11.9 volts.

I kinda like the adjustable power supply but not for this unit. I worry about connecting 5V, 12V and ground to the proper test points - I don't need to add in adjusting anything. I'm thinking about building another power supply that is adjustable from maybe 5 volts to 24 volts with a volt/amp meter. That might be pretty handy to have - and I probably have most of the parts left over from this build.

Adding in the two resistors would be pretty easy to get 13 volts. Would I have the headroom with the 12VAC transformer?



#200 1 year ago

I'd rather not have a trimmer pot inside but would rather just have a fixed resister. On my adjustable power supply I'd like to have a external pot with a knob and volt/amp meters. I been looking a schematics using LM359K for the adjustable power supply. I like the TO-3 case. Also the adjustable supply will only have one output which should make it simpler.

Quench, I can follow instructions and I can follow schematics. The data sheet I looked at indicated 1.5 amps - that should be plenty even with the 5 volt section added. And the meters. Are you saying adding the two resistors would be advantageous. Would I see more than 12 volts? The most difficult part would be cutting the trace - and that's not that tough to do. As long as I have the headroom I think I'll do it.

I'll try not to bother everyone so much with the next one. I guess you all are getting tired on me asking so many questions and asking for suggestions but I do appreciate all your help.



adj ps (resized).PNG
#203 1 year ago

I didn't think the current draw from just the 5V regulator (with nothing attached) would be much. And I did hold 11.9 volts with the 0.53 amp light attached. The only time I've used the 5V section was to test MPUs.

Today I'll pull the PC board and add the two resistors. I'll report back.

Mark, Yes I'm really happy with how this has turned out. I just wanted to see the 12 volt section go over 12V. (I know - 11.9 is really close). I think adding the two resistors like Quench showed in post 197 will put me over.

I have loaded both the 12V and 5V to boot a MPU. It worked great and that's what this power supply is intended to do. As a companion to this I'm thinking about building a 1 to 25 volt variable power supply. Should be easy and I think I have most everything I need left over from this project.



#204 1 year ago

I couldn't be happier. We just built the perfect MPU testing power supply. I added the two resistors. 13.45 volts at the 12V output - 5.31 volts at the 5V output. Then I connected a MPU and it booted fine. Then I scanned the 12V regulator input, 12V output, and the 5V output.

All that's left is to assemble the front panel, install the meters, and give it another test. We've had a lot of discussion about the meters - here's my plan. I'm going to install a volt/amp meter on the 12V - I know it will be reading the amps of both 12V and 5V and that's OK. Then install a volt (only) meter to the 5V. Then install a volt/amp meter to the 24V. I'm not sure but I think that should work.

I'll post some photos of the power supply shortly.

Thanks to everyone.


12 v in (resized).jpg12 v out (resized).jpg5 v out (resized).jpg
#206 1 year ago

I thought the meters would be the easy part. When I received the meters I gave one of each (volts and volts/amps) a quick check on the old power supply. Tonight I started with the 24 volt section (because it would be easiest). I wired it just like the diagram below. Except where the diagram indicates + & - "load" I had + & - output jacks. Meter was dark. I checked with my DMM and had 24 volts. Bad meter? So I opened another meter and tried again - still dark. So I pulled out the 'volts only' meter and connected it (red and yellow to + and black to -). It smoked. At this point I'm really feeling down and quit working on the 24 volt section. I tried the same thing with the 12 section and no meters would light. I checked continuity from the power supply the the back of the meters and it was OK. Then I checked voltage at the back of the meters and I had voltage there. So I quit for the night.
V A meter (resized).jpg
I'll give it another try tomorrow.

Here's some of the latest photos.



IMG_3048 (resized).JPGIMG_3050 (resized).JPG
#208 1 year ago

First photo is a little tour of the outputs. The 24 volt section is independent from the main section - the 24 volt transformer is even on it's switch.

IMG_3048a (resized).jpg
This photo shows how I wired the outputs.

IMG_3058a (resized).jpg
This is the front panel with the output jacks installed.
IMG_3061 (resized).JPG
IMG_3063 (resized).JPG

The front panel is now complete with the holes cut for these meters - so I'm stuck using them. I have 6 meters - 3 volt/amp and 3 volt only.

There's only 3 wires on the volt only meter. Should be simple to wire - red and yellow to + and black to ground. Yesterday when I connected one of the meters to the 24 volt outputs it smoked. Then I connected another meter to the 12V - nothing. Then 5V - nothing. Today I connected it to the old power supply - still nothing. So I opened the third meter and connected it to the 5V - it worked. Then the 12V - it worked. I'm a little scared to connect it to the 24 volt because the last time it smoked the meter.

I tried connecting two different volt/amp meters and neither would light. I even tried connecting only the red/yellow and black to get just voltage and they still won't light. I'm beginning to think these meters are crap. And people wonder why I hate Ebay.

Out of 6 meters I just need to get 3 to work.

Any suggestions?



#209 1 year ago

It's the crappy meters!!! I opened the third volt/amp meter and connected it like before and it works. I even connected the small car bulb and it shows volts and amps. So my wiring is right - the meters are junk. Out of 6 meters only 2 work.

I haven't connected any meters to the 24 volt output today. I guess I'm shell shocked. (and no spare meters). Something I noticed about the 24 volt line is when I connect my DMM it jumps to 30.XX volts for a microsecond then drops to a steady 24.8. I think I read that the meters are only rated to 30 volts. Could that microsecond cause the meter to smoke? Is there anyway to stop that 30 volt surge? Or am I just worried about something that isn't an issue? I'd hate to smoke my last remaining volt/amp meter.



#211 1 year ago

Feeling more confident now, I connected the meters to the 5V and 12V outputs. They worked as planned. I even connected the small car bulb and the volt/amp meter showed the amp draw. Both meters dropped a little with it connected.

I just don't know what to do with the surge on the 24 volt line.



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#212 1 year ago

Mark, The 24 volt section doesn't have a regulator - it's only for checking for zero crossing on the MPU (seventh flash). It's the same setup I had before but it was in a separate box. Just a 24 volt transformer and bridge rectifier.

Would some kind of capacitor or something work?



IMG_1218 (resized).JPGIMG_1220 (resized).JPG
#214 1 year ago

Back when I built this little test box I wanted an indicator light. I knew if I connected just an LED that it would blow out. So I added a small resistor with the LED. See photo above. Why couldn't we do the same for the meter? The small red and black wires provide power for the meter. The small yellow wire is the voltage sense. See diagram below. Would adding a resistor to the small red wire keep the meter from smoking? See second diagram. What size resistor?



meter 1 (resized).PNGmeter 1a (resized).png
#215 1 year ago
Quoted from Quench:

Stick your oscilloscope on that rail and you'll see the peaks are around 33 volts.

Strange you should mention that. When I built that little box I had just got my first (USB) oscilloscope. That was my first encounter with RMS.


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#216 1 year ago

I just keep getting more confused. Thinking about my theory of adding a resistor to the 24 volt line. First I checked the 24 volt with the scope. It shows 38 volts on the peak. I'm sure that's what caused the meter to smoke. So I added a 100 ohm resistor to the + terminal. Then I probed the other end of the resistor (expecting to see the voltage to go down). It didn't. Then I replaced the 100 ohm with a 10K ohm. No change. What am I doing wrong? Why don't the voltage drop?



24 volt (resized).jpg
#217 1 year ago

It's real late but my dog needed out so I took him out thru the shop. While he was out I pulled out the LED and resistor that was connected together in the old box.The resistor measured 0.465K ohms. I connected them to the 24 volt + and -. When I probed on each leg of the LED and got this. That's what I was expecting to see before.Somehow the LED needed to be on the load I guess.

I'll mess with this more tomorrow - I gotta get some sleep now.



led & 0.468k resistor (resized).jpg
#220 1 year ago

I think the meter I have is the 100V version:

ebay.com link

This is the specs:

meter specs (resized).PNG

The meter doesn't need to be bang-on accurate. I'm happy if it's somewhere in the 24 volt range.

I think the meter smoked because I over powered the LED part. The specs show "power supply range 4-30VDC". I think the 38 volt peak is what killed it. The meters work fine on the 12V and 5V. I just need to power the LED part with lower voltage. That's what the small red and small black wires are for (I think). I read that you can power the meter with just a 9V battery on just those 2 small wires. The small yellow wire will read the voltage. I just need to get the voltage down on the red and black wires. Something like what I showed in post 214 - a resistor or resistor/zener in the red wire. How would I connect that and what values to use?

Mark, you're right that I was reading the resistors with no load. That's why late last night I tried the resistor and LED. And it worked. 1.6V mean. But that might be too low to light the meter. "power supply range 4-30VDC". Also the specs show "operating current less than 20mA".

With you guys great help I think I'm on the right track. Just need to figure out how to get the voltage down a little.



#222 1 year ago

I don't have a bunch of 2W resistors. Most are 1/4 and 1/2. I do have a load of 5 and 10 watt - 1 to 100 ohm.

I just ran across this on Amazon:

amazon.com link »

It's just 2 inches X 1 inch and would fit nicely on the right side of the case (next to the 24 volt outputs). Would this solve my problems?

I'm gathering parts for my variable power supply. The meters I'm going to use suggest powering them with a seperate power supply. I think this would work there also.



IMG_3048 (resized).JPG
#224 1 year ago
Quoted from mbwalker:

What's the DC voltage coming out of the rectifiers?

24V mean - 38V max. - see post 216 for scope scan.

What do you think of the little 24V to 12V step down converter? Would adding it cause any adverse affect on the 24V ripple for the zero crossing?


IMG_3054a (resized).jpg
#226 1 year ago
Quoted from mbwalker:

What does the voltage on the other bridge look like?

I'm not in the shop right now but the first scan in post 204 shows the input into the 7812. That's coming from the 12 volt bridge.

Thanks for checking into the converter.

Quoted from mbwalker:

If it was me, I'd just stick in a resistor, zener, and a filter cap and call it a day.

If I had the electronics knowledge that you guys have I'd probably do that too. But I'm getting a headache from messing with these meters. And this was supposed to be the easy part.



#228 1 year ago

Don't feel bad - I've read this thread 8 - 10 times from front to back but after 200+ posts even I get confused.

I thought about doing the same thing except I was going to get the power from the output terminals of the 12 volt. That's what's powering the 12V and 5V meters so it should work fine. The down side is the 24V meter will light even when the 24V supply if off. (but show all zeros). I wanted to keep the 24V section separate because I seldom need to check the zero crossing. The 24V transformer is even on it's own switch.

I've ordered two of the 24 to 12V converters. One for here and one for the adjustable power supply. I think they'll work OK.



#231 1 year ago

I learn something new all the time. Look at the drawing below - if there is something in the green box on the right (capacitor, etc.) it would have an effect on what's going into the "line out A". I didn't know that! Seems to me that what's going on on one side would have no effect on what's going on on the other side. (like a fork in the road). Very interesting.

If I put a diode (as shown in the second drawing) it would keep the capacitor from effecting the line out A. Do I need to add a diode to the negative line also?

No wonder this electronics stuff is so complicated.



converter (resized).jpg
#233 1 year ago

On the adjustable power supply I was going to tap into the lines from the bridge rectifier for the 24 to 12V converter. Would I need a diode it there also?

Would it hurt to put a diode there?

See drawing.



adj converter (resized).jpg
#236 1 year ago
Quoted from mbwalker:

Let me see if I can find the overall schematic in the earlier posts.

This might save you some time:
adj ps 1 (resized).png

I've omitted the parts for the meter.

I never thought this project would take so much time. I apologize for that. I hope there are others following along and learning something. I know I've learned a lot the last few weeks. And I appreciate you guys teaching us.

Quoted from Quench:

Is your variable power supply also going to have a zero crossing output?

No - but I could use it to jumper across a trace on the back. (or I could just use a jumper wire). I'm working on the PC board layout now and I'll post it when it's complete.

Quench, I know you mentioned a switch mode power supply - but I've already ordered the parts for this LM350. From what I've read this power supply has been around a long time and the only concern they have is the heat from the LM350. I've considered that and ordered a big heat sink. Hopefully I won't have any problems and it won't be used too much anyway.



#239 1 year ago

Quench, I dropped the idea of the diode - The converter will be hardwired to the board anyway so I don't need a jumper to cross the trace.
See PC layout below.

Mark, I can't answer that yet - I haven't built anything yet. This is the transformer I'm going to use.


With that and the layout below, you may have a better idea of what the voltage would look like.

Look this over and see if I screwed up anything.



pcb layout adj 5 (resized).jpg
#241 1 year ago
Quoted from mbwalker:

Looks like you are missing a connection.

Good catch - I been working on that all day and it took you what, 2 seconds to find?

Quoted from mbwalker:

I would not be surprised that you can run the meter directly without the DC-DC converter.

I considered that but the meter is only rated to 30 volts. This transformer says 24 volts (just like the zero crossing transformer) and I cooked a meter with the other transformer. The converter seems like good insurance (I hope). We'll see - the converters and new meters should be here Saturday.

Thanks again for finding my mess up.


#242 1 year ago

I got the meters and converters today. Meters all work fine now. Before I connected the converter to the zero crossing section I scanned the output with the scope.
nothing connected (resized).jpg

Then I connected the converter and scanned again. You were right - no more ripple.

converter connected (resized).jpg
Then I put in a diode (1N4007) in the + line. This brought back the ripple but at a little loss in voltage (0.4) and I noticed the peaks are a little cutoff on the tops. Will this affect the zero crossing?

converter connected w diode (resized).jpg



#245 1 year ago

From looking at your measurements back when you found that guy on solar panels I didn't think it would be a problem. And it isn't. I just booted a MPU and it booted fine - including zero crossing.

Mark, big difference from before diode and after.

before diode (resized).jpg


after diode (resized).jpg

I connected a meter to the zero crossing and it works but it's jumping all over - from 18V to 30V. It looks like something on life support so it may be a connection somewhere or a bad meter - but the meters were fine before. I'm still working on it.

IMG_3093 (resized).JPG
#247 1 year ago

That was it, except now the meter reads 36.2V. The output terminals read 24.4V with my DMM. After diode reads 36.2 also with DMM.

Do you think the meter will adjust down that far or is there something else I can put in there to drop it down to 24V?



#249 1 year ago

Not much adjustment there - 35.1 to 37.5.

Never made a voltage divider. This would be my guess.

Any idea of the size of resistors?



IMG_3103 (resized).JPG
#251 1 year ago

Mark, when I connected the meter to the 24V output - it worked but the meter was bouncing around too much. Quench suggested it was because of the ripple for the zero crossing. He suggested connecting the sence wire after the diode. That worked but now the meter reads too high. I've tried adjusting the meter but it won't go down enough. It reads about 36V - I want it to read the output volts - 24 volts.


#253 1 year ago

I never thought a meter would be this complicated. I thought adding the 24V to 12V converter would solve my problems. Building the entire power supply wasn't this difficult.

#256 1 year ago
Quoted from mbwalker:

Then you need to add a resistor and a capacitor on the sense line to smooth out the ripple. Doesn't affect the 24V output.

Where? If I add it before the diode (where I need to measure the voltage) won't it affect the ripple on the output (like the converter does)?

If I add it after the diode will it change the voltage reading on the meter?

#262 1 year ago
Quoted from mbwalker:

Plus I like to chime in at 2 AM half asleep and derail the postings. Wife is out of town, so I don't have anything else to do.

Thanks Mark. I got a big laugh out of that - something I needed after a long and "not productive" day in the shop. This morning when I received the meters and converters I thought I'd slap them in and be done. Boy was I wrong.

I found some 22uF electrolytic caps. I think I have some 10K resistors. (I gotta sort out my component collection).

The one thing I was trying to avoid was having a bunch of components just stuck in there (like my old power supply). Now it looks like I may have to add resistors, diodes, capacitors, etc. I thought I might just add those to a seperate little PC board. Then I thought I might as well omit the converter and add a small PC board with the diode, zener, resistor and filter cap that you both suggested back around post 229.

I'm going to have to think about this for a while.



#263 1 year ago

Seems to me (for what little I know), that adding the resistor and capacitor (without the diode) like Mark shows would have the same affect as the converter in smoothing out the zero crossing output.

If I go the 'diode, zener, resistor and filter cap' route, how would that be wired? What values should I use.



#270 1 year ago
Quoted from Quench:

Say a 4.7k and 2.2k with the 4.7k on the lower side?

The 4.7k on the negative side?

I'm going to try this first today.

If that don't work I'll try the 'diode, zener, resistor and filter cap' route. Anyone have a schematic for that?



#271 1 year ago

Quench, your resistors were right on the money, meter shows 24.5V - DMM at the output shows 24.57V. I'm impressed.

I'm not going to tell you that I misread the numbers and used a 47k instead of 4.7k the first time.

I just need to check for amps then clean this up a bit.



#272 1 year ago

Much better day today. First I finally got the meter to show the proper voltage. Then I tried the amps. I connected two 12 volt car bulbs in series - the voltage went down a little (2 volts) and the meter showed 0.22 amps. But by this time my workbench looked like colorful spaghetti. I took several photos and made a sketch to help me remember how it goes together.

IMG_3104 (resized).JPG

I figured there's no way I'm going to stuff all that back into the box. So I made a little printed circuit board.

IMG_3120 (resized).JPG

Then I attached everything related to the meter to the board. Now all I have to do is connect everything up and test it out one last time. Everything has worked before (it even booted up an old MPU - all seven flashes) so it should work after I get it all connected. I have some errands to do but hopefully I'll have it all together in the next couple of days.

Thank you all for your help and suggestions.


IMG_3127 (resized).JPG
#274 1 year ago
Quoted from Quench:

I suspect the 7812 dropout voltage is part of the problem.

The 7812 doesn't play here. This is unregulated 24V for the zero crossing.

I haven't made up a molex connector yet - I'll probably do that soon. The down side is most of the time when I work on MPUs the connector headers are removed or unreliable so I couldn't use the molex connector anyhow.

I tried that LTSpice a couple of weeks ago. Way over my head. You guys are amazing.



#281 1 year ago
Quoted from mbwalker:

Bob, what current is the 24V transformer rated for?

I don't know much about the 24V transformer - I got it from Radio Shack a while back. They don't list it anymore.

Quoted from mbwalker:

And what part number is the bridge?

IMG_3139 (resized).JPG

Quoted from mbwalker:

Just measure the VAC at the bridge input, with and with out a load. That tells us a lot.

I'll do that tomorrow - I'll have more time.

Quoted from Quench:

I'm the opposite, I don't start testing until I've replaced the headers - working on too many corroded boards

I guess that's my confidence level. I don't want to invest in headers until I know it's going to work.

More good news coming. Stay tuned.


#282 1 year ago

I was a hurry to get into the shop tonight because I knew I was close. Getting everything connected wasn’t easy but my sketch and photos helped. Also it’s beginning to get cramped in there. But I got it all connected and it works great! I checked the voltages at the output terminals with my DMM and the 12 volt was just a little low (maybe 0.2V). Tomorrow I’ll adjust the 12V meter, scan the outputs with the oscilloscope and see if it will boot a MPU. Then I can close up the case. I think I’ll call this my “PinSide Tester”.

Parts should be here for the adjustable power supply by the end of the week. That gives me a couple of days to clean up my bench – looks like a bomb went off. With all I’ve learned here, the adjustable power supply “hopefully” will be easier.

If anyone is interested in photos of this build, I’ve uploaded a ton of photos here:


Thanks again for all your help.


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#286 1 year ago

First I made a minor adjustment to the 12V meter. It's reading the same as my DMM at the output. Then I scanned the 24V before the rectifier (no load):

5 (resized).jpg

Then I connected a load (two 12V car bulbs in series - 0.24 amps). :

3 (resized).jpg

#287 1 year ago

This is the completed power supply. It really looks nice setting on my workbench shelf - ready for the next MPU.

IMG_3173 (resized).JPG

IMG_3177 (resized).JPG

IMG_3189 (resized).JPG

I'm not sure I have an 'as built' schematic. I found a PC board layout with the components but I know we added two resistors to boost up the 12V a little. I can't find any revised schematic showing the added resistors. I agree that it's something I may need in the future. I'll work on that.

Next up is the adjustable power supply. Parts should be here tomorrow.

adj ps (resized).PNG

We gotta find something for Mark to do for the next few days - you know what they say about idle hands.

Thanks again everyone - couldn't have done it without you.


#288 1 year ago

Mark, I couldn't find a final schematic. This is the PC board layout with the components and the added two resistors.


Final layout (resized).jpg
#291 1 year ago

You caught me just in time - I was about to etch the board. I widened the trace to pick up the resistor. What size do I need to add?

I think I'll stay with the LM350K. The LT108's look like TO 220's. I'm partial to the TO 3's - old school I guess. And besides I have the LM350 already.

I'll probably start assembly tomorrow.



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#292 1 year ago

For those who have been following for the Meteor re-setting problem, I think the problem is fixed. I’ve played over 100 games without one re-set.

A brief review – The game was re-setting every once in a while. It had a Rottendog solenoid driver board and the 5 volt regulator was getting very hot (maybe that’s normal). I replaced the driver board with an original board. I tested it for a few games and it re-set again. Next I removed the lower right flipper coil to replace the diodes. I found the coil sleeve was stuck so I replaced the coil and diodes. Then I replaced the diodes on the upper flipper. This seems to have fixed the problem. I think the problem was the coil was getting hot, the winding would expand and the coil would short out. Then it would cool down and the short would open again.

Thanks to everyone who made suggestions.


#294 1 year ago

Update on the adjustable power supply. I got the board assembled yesterday. Today I worked mainly on the front panel. Tomorrow I'll letter it. If you were making this would you letter it (where the ???? are):
front panel a (resized).png

While waiting for the paint to dry on the panel I connected the board. I don't have the meters connected so I used my DMM. It works!!! 1.25V to 26V. I'll connect it to my oscilloscope tomorrow and see what the wave looks like but so far I'm impressed. Just think 6 months ago I couldn't have done this - I wouldn't have even tried. You guys have taught me a lot - thank you all.
IMG_3222 (resized).JPG
IMG_3229 (resized).JPG

Mark, your wife has just been playing with you. As soon as she returns she'll set a new high score.She just wanted to give you something to shoot for while she's away.



#296 1 year ago
Quoted from Quench:

Are you going to print 1.25V and 26V (or whatever maximum is with a minor load) at the minimum and maximum sweep of the rotary control?

No but I would like to put on a sweep symbol like this:

potentiometer-icon-vector-450w-1241247724 (resized).jpg

Don't know how to make it.


#298 1 year ago

I knew it was too good to last. Looking at the PC board in post 294 above, there are two blue terminal blocks. The one on the right connects to the potentiometer - the one on the left comes right off the rectifier for the 24V to 12V converter. Yesterday when I checked the left block it read 24 volts. And it didn't vary with the output (turning the pot). Today I connected the converter and the output read 12 volts. Then I connected the volt meter to the converter (and the sence wire to the output) It read fine and showed the variable output. Then I connected the Amp meter. When I turned it on both meters lit for a second then went dark. I disconnected the converter and tried the power supply again. Nothing. I found the 3 amp fuse from the transformer to the rectifier was blown. I replaced the fuse and tried the power supply and it works again. But when I checked the terminal block for the converter it now reads 36 volts.

Do you think the rectifier is blown? What would cause it to blow?



#299 1 year ago

I did some more investigating. Using my DMM - 26.3VAC at the transformer (AC input). 35.06 VDC at the bridge rectifier output. It was 24VDC yesterday.

Then I connected my oscilloscope The first scan is at the AC input. The next scan is at the rectifier output.

at trans 1 (resized).jpg

after rectifer (resized).jpg

Then to be sure I went back and scanned again. The AC input looked the same but the rectifier scan looks like crap. I've never seen a waveform like that.

after rectifer1 (resized).jpg

Could this be the problem?

This is the rectifier I'm using:


I just ordered 14 different rectifiers from Arrow. They should be here in a couple of days.



#300 1 year ago

Well I seem to be getting more lost everyday. First I checked the meters to see if they still work. I connected each one (volts and amps) to my Pinside tester (on the 5V output). They still light up fine. Then I checked the 24V to 12V converter by connecting it to the zero crossing output. 24 volts in - 12 volts out - it's fine. Nothing blew up yesterday - good news.

Then I checked the adjustable power supply. 26 VAC in and 34.75 VDC out at the rectifier. Then I connected it to my scope. The AC in was exactly the same as yesterday (see first photo above). When I checked the 'after rectifier' I got almost exactly the same as photo 2 above. When I checked again I got the same messed up wave as photo 3. That's when I noticed I wasn't making good connections. I added a couple of wires to get a good connection and now the scope shows a steady output (but still high).

I'm concerned about putting 35 volts into the converter may blow it up. Could that be what blew the fuse? I still don't know what caused that.



IMG_3235 (resized).JPGafter br monday (resized).jpg
#302 1 year ago

The bridge seems t