Meteor Resets – With Rottendog Solenoid Driver Board

(Topic ID: 229354)

Meteor Resets – With Rottendog Solenoid Driver Board


By oldschoolbob

29 days ago



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  • 127 posts
  • 13 Pinsiders participating
  • Latest reply 1 day ago by oldschoolbob
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  • Meteor Stern Electronics, 1979

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There are 127 posts in this topic. You are on page 1 of 3.
#1 29 days 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.

Thanks

Bob

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#2 29 days ago

I've usually found it's the large capacitor on the SDB that's bad whenever I've had reboot issues. I guess you can at least narrow it down to that board if you feel like pulling the SDB out of your F2K and putting it in the Meteor to test. You can use any electrolytic cap from 10,000uF to 15,000uF of at least 25V.

#3 29 days 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:

https://www.greatplainselectronics.com/proddetail.asp?prod=CER-10000uF-35V

Thanks

Bob

#4 28 days ago

5.7v from a fixed LM1085 5v regulator does not sound right.... are you sure that is what it reads? They should be much closer to 5.0v

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. I bet that sucker gets hot as sin tho... I tried a LM1084 in a gottlieb s80 game once. Even on a big heatsink it overheated in about five minutes. Bally is obv lower current tho since rottendog is using this regulator.

Do note that LM1084/LM1085 has a different pinout than the 7805 series to220 regulators, so don't try one of those. There is also adjustable voltage versions of these regulators. Double check the part number's suffix which gives the voltage rating. LM1085-5.0 is the 5v part. If an adjustable version is used resistors will be nearby to set the voltage (maybe how you can see 5.7vdc??).

#5 28 days 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?

Thanks

Bob

#6 28 days 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.

Bob

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#7 27 days 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?

Bob

#8 27 days ago
Quoted from oldschoolbob:

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?
Bob

Lot of possible causes but most often cause of resets i run into is bad connectors at mpu j4 and driver j3. next up would probably be bad ic sockets.

usually you can detect voltage drop across the connectors by checking voltage at the mpu using its ground and 5v tests points. gently tapping, twisting and flexing on the mpu board can reveal a flaky ic socket connection.

i dont know how consistent the resets are but you could monitor the 5v and watch when it starts to reboot. If the 5v goes flat for a few seconds then comes back and then the cycle continues as the regulator gets hot / cool, then it is probably over heating.

#9 27 days ago

I don't trust Rottendog boards from my experience many years ago, things may be better today but there are better new alternatives out there, namely Alltek. Not saying you don't have a problem with your SDB, but another cause of resets on classic Bally/Stern is a cracked flipper diode. Might want to take a peek at those right flippers.

#10 27 days ago

I've been using EZSBC's PSU5 on Bally/Stern solenoid driver boards to replace LM323K's. They work great. The only caveat is that you'll need to jumper over the resistor (R50 - 4.7ohm) that Bally/Stern used to offset the 5V slightly to account for voltage drop (5.25V or there abouts). The PSU5 will oscillate and not function properly without the case tied directly to ground.

You can even remove the large heatsink - the PSU5 won't need it.

https://www.ezsbc.com/index.php/psu5.html

#11 27 days ago

Andrew,
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.

Brian,
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.

Corey,
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.

Bob

#12 26 days ago
Quoted from oldschoolbob:

Corey,
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.
Bob

A lot of current travels through that ground connection. I recommend pulling R50 and installing as heavy gauge wire as will fit into this location.
Smaller gauge wire can result in a tiny voltage drop through the wire which reduces the efficiency of the PSU5 regulator.
Ed

#13 26 days 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.

Bob

1 week later
#14 14 days 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?

Thanks

Bob

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#15 14 days ago
Quoted from oldschoolbob:

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.

At which point are you measuring this?
BTW the upper soldered side of that black wire ground mod looks awfully close to the 5V trace. You might want to move the end of that wire slightly up on the ground trace where there's no chance of it shorting.

#16 14 days 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.

Thanks

Bob

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#17 13 days ago

So when you hook up your power-supply, is TP3 on the SDB measuring 5 volts DC?
The only load on the output of the SDB's regulator (thanks to the TP3 wire mod) is the 74L154 chip at U2 which should be very low.
The voltage drop you're getting on the power-supply is a little strange. I presume it has its own regulator on the back. Note the big capacitor at C23 on the SDB will appear like a short circuit on power-up so maybe it's affecting your power-supply's regulator not to be able to recover properly. You could hook up your oscilloscope to compare disconnected vs connected.

#18 13 days 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.
IMG_2500 (resized).JPG
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.

Thanks

Bob

#19 12 days 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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#20 12 days ago

Hmm, I was expecting more of a dramatic difference.
Once C23 on the SDB charges up, the SDB should represent very little load (presuming you have nothing connected to the 5V rail off the SDB) and so the input 12V shouldn't really drop.

I can't quite tell how that rear 12V regulator is wired - are there any model number markings on that regulator?
But it looks to me like the two black capacitors in parallel have the positive legs wired to ground...

#21 12 days 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.

#22 12 days ago

Bob - I know you like your power supply, but if you're in doubt of it, go to a computer recycling place and get an AT power supply. It has the regulated 5 and 12 volts, along with other voltages. Very cheap, possibly free.

Caps are additive in parallel, average in series - opposite of resistors.

Let's not go down the rabbit hole - lets figure out the board issue. )

#23 12 days ago
Quoted from oldschoolbob:

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

We're talking about pretty much straight away. The question is what voltage are you reading on the output of the bridge rectifier? And whats the output voltage of the transformer rated to?

In reality here, you really want to bypass that 12V regulator for testing your SDB. The SDB 12V should be connected to the output of the rectifier only. If you really want to do it properly, add a switch so you can disconnect everything related to the powersupplys 12V regulator for testing SDBs, i.e. so the SDB gets unregulated DC just like it would in a pinball.

Quoted from oldschoolbob:

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.

The point is it looks like those two caps are wired in backwards. Positive leads are connected to ground, negative leads are connected to + voltage.

#24 12 days 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.

Bob

#25 12 days 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?

Thanks

Bob

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#26 12 days ago

I think the red ??? Is a zener diode.

#27 12 days ago
Quoted from oldschoolbob:

When I repaired my first game I used an AT power supply. When I couldn’t get it to boot at the bench

I use an old AT powersupply for bench testing. I have problems with some MPU boards (mostly Sterns) because their VR1 8.2V zener diodes are underspec and measure 7.7V which causes the valid power detector circuit to sometimes fail due to the different rise times of my AT power-supply rails. When I manually reset the MPU boards they always start up. My OCD always makes me install new 8.2V zener diodes on MPU boards in this scenario even though the ones running at 7.7V usually work fine in pinball.

Quoted from oldschoolbob:

But, when testing MPU’s would I want regulated or unregulated?

The 12V needs to be regulated for testing MPU boards otherwise the valid power detector circuit will fail.
For SDBs though you can have either. Without knowing the full details of your powersupply, what you're seeing could be normal. If you want to properly simulate pinball, unregulated 12V will allow you to check how well capacitor C23 is filtering ripple.

Quoted from oldschoolbob:

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.

Quoted from oldschoolbob:

I found that the chassis is connected directly to the positive of the bridge rectifier (I don’t like that at all)

Ahh, it's not a regulator on the back, it's some sort of TO-3 case transistor. And the transistors collector is mounted directly to the chassis which is why the chassis is "+12V live". You will need to completely isolate the case of the transistor from the chassis (with insulators) in order to be able to redesign the chassis to be ground. You currently have an accident waiting to happen if the power-supply case touches something it shouldn't.
So the caps are currently installed the right way around.

Quoted from pintechev:

I think the red ??? Is a zener diode.

Spot on, very likely it's a zener diode.
You should check the markings on it to find out what zener voltage it is so you can understand what the nominal output voltage of this power-supply should be.

#28 11 days 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.

Thanks

Bob

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#29 11 days 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?

Thanks

Bob

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#30 11 days 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.

Thanks

Bob

IMG_2880a (resized).jpg
#31 11 days ago

1N4744 is a 15V 1W zener diode. If you're measuring 14.68 volts at the bridge rectifier output then this zener voltage is too high and won't regulate the output to a constant voltage (which is what you are seeing). The zener voltage needs to be lower than the bridge voltage output.

You need to isolate the transistor from the chassis so you can then modify the circuit to connect chassis to ground.
One of these is needed between the transistor and heatsink:
https://www.greatplainselectronics.com/proddetail.asp?prod=SP400-0.009-00-03

One of these will be needed to isolate the transistor screws from the heatsink:
https://www.greatplainselectronics.com/proddetail.asp?prod=18PTI1HDWOB

The output of the bridge will need to connect to the transistor screws (use a lug with screw hole) which are bolted to the transistor case.

If you want, hook up your oscilloscope to output from the bridge rectifier so we can see what voltage peak it's reaching which will help select a better zener and C1 cap. R1 might also have to be changed.

Your other (easier/safer) option is to just use a 12V regulator..

Below is the schematic you have: I didn't add that diode on the output - actually its only purpose is to protect the transistor if you connected a higher external voltage source onto the output of the power-supply - chance of you ever doing that??? I'd get rid of it since it's dropping the output by 0.6V

Simple_PS.jpg

#32 10 days 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.

Thanks

Bob

#33 10 days ago

I thought you might need a good laugh today. My Schematic:
IMG_2902 (resized).JPG
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.
IMG_2908 (resized).JPG
IMG_2907 (resized).JPG
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 10 days 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.

#35 10 days ago

It could be the known bug in the code:

"It's only happened to me twice in many many many games. You need 7x bonus, and then hit the spinner, then get collect bonus on the outlanes. Think that's the way it works....

https://groups.google.com/forum/#!topic/rec.games.pinball/hqY7fAb2E28"

#36 10 days 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.

Thanks

Bob

#37 10 days ago
Quoted from oldschoolbob:

I thought you might need a good laugh today. My Schematic:

Quoted from oldschoolbob:

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.

Your oscilloscope shows the AC waveform is a sine wave. If you look at the sine wave on your graph, the peaks reach about +17 volts and -17 volts (the centre of the graph is zero volts). So from peak to peak you have a total of 34 volts. This isn't 34 volts constant usable voltage though. The 22.8V listed on your scope is calculated RMS (root mean square) although this listed value is + peak to - peak which we don't usually refer to. Normally we just refer to RMS value on one side of the wave which in your case makes would make the calculated value 11.4VAC RMS (close to the 12.6V rating of the transformer taking into account tolerances, calibration errors, etc).
A quick look here will explain RMS:
https://www.electronics-tutorials.ws/accircuits/rms-voltage.html

So simply put, the 17 volts peak you see multiplied by 0.7071 (RMS factor) is where the voltage rating for the transformer comes from.

Without a load hooked up, those two 1000uF caps are filtering out all the ripple on the DC side and they're keeping the rectifier voltage up at the peak you see in the second waveform - hence you see a constant 17 volts DC in the first waveform. If you hook up a 12V lamp on the output of the power-supply, you should see some ripple on the rectifier output as the capacitors haven't stored enough energy to keep the voltage flat.

#38 10 days ago

Here’s the way I understand RMS. This is a wave form (or half of a wave form):
wave 1 (resized).jpg

If we could fill that up with water, we’d have a certain volume of water in there:

wave 2 (resized).jpg
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.
Thanks
Bob

#39 10 days ago
Quoted from oldschoolbob:

I must be reading the oscilloscope numbers wrong. You said the peaks reach +17 to -17 for 34 volts peak to peak.

Ah, I didn't see the 10V/division on the AC waveform, I just presumed it was 5V/div like the previous DC waveform! But 66 volts peak to peak from a properly functioning 12.6V transformer??? I think you've discovered a bug in that Hantek software. If you count the divisions as 5 volts each, the readings make sense and align with the rectifier output graph voltage with filter caps and no load.

#40 10 days 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.

Bob

#41 10 days ago

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

Bob

#42 9 days 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?
pic_44_2 (resized).jpg
pic_44_1 (resized).jpg
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.
12 and 5 volt power supply (resized).jpg
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.

Thanks

Bob

#43 9 days ago

Nice work.

Connect the input of the LM323 to the unregulated output of the rectifier. You could use a single 15,000uF cap to replace the 10,000uF and 2,000uF caps.

In the 5V regulator section, you want the small capacitors physically close the the actual regulator. See the note from the datasheet below (LM123 is same as LM323 but with higher operating temperature range).

Quoted from oldschoolbob:

it made me think about the 10X probe setting. So I changed the probe to 1X and re-scoped.

It still doesn't quite make sense why your scope gave you those initial readings. X10 on the probe merely divides the input by 10. So you should have got readings of 1.7V peak instead of 17V peak. Where that 34V peak on each side is still a mystery.

Have you updated the ROM on the MPU board to fix the scoring bug?

LM323_Caps.jpg

#44 9 days 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.

Bob

#45 9 days 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.
12 and 5 volt power supply r1 (resized).jpg

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.

https://photos.google.com/album/AF1QipO7mO0CghiGS9pP7Mt4-O2wfuYGDycm_BdxlsG5

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.
probe (resized).jpg

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.

Thanks

Bob

#46 9 days ago
Quoted from oldschoolbob:

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?

C1 and C23 are on the same circuit now, so you're pretty much putting the cap on the rail.
You might want to add some fuses too.

I can't access your photo album - it requires google login which I don't have. Do you need to set it as public?

So you can refactor the voltages on your scope if you are attenuating at the probe.

#47 9 days ago

I think I made it public now. Try again.

Or try this link:

https://photos.app.goo.gl/LcDp6v6B4QzjBjFP7

#48 9 days 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.

Thanks

Bob

12 and 5 volt power supply r2 (resized).jpg
#49 8 days ago

Oldschool,

First off, congrats for you working on this. Good to see people taking an interest in really learning what is going on rather than just changing parts. And you have a scope! A+

Quench is giving you some really sound advice. Kudo's to Quench too.

So I'm a little late to the party here... I got a little confused reading the thread, seems like we are jumping back and forth between the 12V, the 5V, and boards in games. So apologies if I missed something. I likely did. My primary job isn't designing power supplies, but I do it away since we tend to add regulators to our own boards to ensure a good, solid supply. Not an expert by any means tho. The LM323's are pretty much standalone parts. A SinpIt from the TI data sheet is below. Pay attention to the capacitor on the input. Typically what is important besides being at least a 0.1pF, is the cap has a low ESR. While I'll add a large cap in my designs, sometimes large, cheap capacitors aren't low ESR, at least at the frequency frequencies of interest. It not uncommon to add, say a decent 0.1uF right at the input to the regulator in addition to the larger cap. If I'm not mistaken, it also keeps the internal loop of the regulator stable. 15,000uF is a fair amount of capacitance At the input. Keep an eye on inrush current charging that cap (not sure if you know how to do this). An inductor there might help. The ground on the LM323...in your case, that's the '-' line coming from the bridge and cap. Simply wire it like below. The SnipIt shows a LM123 - that's just a different flavor of the LM323. It's wired the same. If everything works w/o the 0.1uF, then don't sweat it.

Q1: That circuit should work, but it's pretty barebones. The zener (ZD1) sets a reference voltage on the base of the transistor, and the emitter is simply a diode drop (0.7V) below that then, but it can supply high current. If the base current isn't adequate, then potentially it won't regulate under load. This is defined by the 'beta' of the transistor. R1 sets the current thru the zener and base, and C2 is just to filter off any noise on the base. If C2 wasn't there, any ripple on the base would also show up on the output (i.e. with ZR1 and C2, you should have a nice quiet reference, therefore the emitter would follow suit). Honestly, the Q1 stuff...just pitch it and put in a linear regulator, like a LM137 (if 1.5A is enough). There's hundreds to choose from, and all would be far better than the barebones +12V regulator you have.

Since it appears you have a knack to learn the basic details, I highly encourage you to download LTSpice (free) which is a simulation tool by Linear Tech (since bought by Analog Devices). They make hundreds of regulators for the industry...you can simulate all day long and not burn up a single part!

Here's a link for LTSpice: https://www.analog.com/en/design-center/design-tools-and-calculators/ltspice-simulator.html It's rather impressive for free. I even use it despite having the expensive simulators to use since the library of their parts are included for free, and the models have been excellent so far. I'll help you get going w/it via PM's, if needed. Or you can post here, but I didn't want to derail your thread.

There's a lot I skipped or glossed over in my comments, holler if needed and I can explain (maybe).

Capture (resized).PNG

#50 8 days ago
Quoted from oldschoolbob:

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

The cap must be before Q1. It needs to filter the ripple coming out of the rectifier so the regulator circuits have a somewhat stable voltage source above regulation voltage. You can then omit the two 1000uF caps.

mbwalker, thankyou for your input. I don't think I explain things well sometimes so your response is very helpful

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