(Topic ID: 282814)

Gottlieb System 80 Power Supply advice

By adfit

10 months ago


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  • 32 posts
  • 8 Pinsiders participating
  • Latest reply 10 months ago by gdonovan
  • Topic is favorited by 1 Pinsider

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#1 10 months ago

I am working up a Volcano ('81) - just starting out in this hobby. Been reading all about making sure the power supply is reliable before plugging all the boards into it.

I am getting along OK, but could really use some advice on the board rebuild (or maybe the bottom board...)

I have detailed what I am seeing here.
https://pinside.com/pinball/forum/topic/first-restoration-gottlieb-volcano#post-5988941

Basically, I'm not sure if I have that right voltages arriving at the board or if rebuilding the board itself will do the trick...

This maybe should have been posted in this section? Huge thanks just for reading this!

#2 10 months ago
Quoted from adfit:

I am working up a Volcano ('81) - just starting out in this hobby. Been reading all about making sure the power supply is reliable before plugging all the boards into it.
I am getting along OK, but could really use some advice on the board rebuild (or maybe the bottom board...)
I have detailed what I am seeing here.
https://pinside.com/pinball/forum/topic/first-restoration-gottlieb-volcano#post-5988941
Basically, I'm not sure if I have that right voltages arriving at the board or if rebuilding the board itself will do the trick...
This maybe should have been posted in this section? Huge thanks just for reading this!

Rebuild all the way! Go for the adventure and learn.

#4 10 months ago

OK, I'll commit to the rebuild!

solarvalue Thanks for the great link. My voltage readings look a out in similar ways to yours when you started the job.

How can I tell if I have the right voltages into the board at J1?
https://pinside.com/pinball/forum/topic/first-restoration-gottlieb-volcano#post-5988944

#5 10 months ago

I have done rebuilds and just replacements with a Gulf Pinball unit.

Getting the board separate from the heatsink and back together is tricky, unless you have the right tools pop for a new Gulf board.

#6 10 months ago
Quoted from gdonovan:

I have done rebuilds and just replacements with a Gulf Pinball unit.
Getting the board separate from the heatsink and back together is tricky, unless you have the right tools pop for a new Gulf board.

Gulf Boards are not the greatest, I would rebuild it, do the ground mods and be proud you fixed it yourself. Anyone can spend money and buy a new board, but learning is fun. The tools you need are not that expensive and are worth the investment. Get your feet wet, take your time, the group is here to help.

#7 10 months ago

Rebuild it.
Procedure is here:
https://www.pinwiki.com/wiki/index.php?title=Gottlieb_System_80#Recommended_Updates_and_Repairs_for_the_System_80.2F80A_Power_Supply_Board

I've rebuilt dozens of them. Once done, they are ready for the next 30 years.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#8 10 months ago

Thank you ChrisHibler - I am following that very carefully now.

So far I have switched out all the parts with a yellow star, but tests look like:

5v = 5.1v and trims fine with the trimmer that's there
8v = 9.9v
42v = 0v
60v = 82v

and I'm blowing fuse F7...

I couldn't get your recommended parts for C1 or Q2, so waiting for "the internet" to post them to me!

I'll swap those and see about the fuse, then I'll update in here.

Thank you again!

PXL_20201202_214604491 (resized).jpg
#9 10 months ago

Is that R10 a 680 ohm?
The cap at C2 is a non-polarized cap.
You really should put a "normal" polarized cap in there.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#10 10 months ago

Two threads going with same topic.
https://pinside.com/pinball/forum/topic/first-restoration-gottlieb-volcano#post-5988944

R10 is a 680 ohm, 1%. 1% not needed but tighter tolerance won't hurt anything. Appears to be 1/4W resistor but will only be dissipating about (4*4)/680 = 0.023 Watts. To me - the color code says the part is actually 690 ohms which is a common value for 1% values. Blue, white, black, black, brown. But.. I suppose the white could be gray. Either way - 680, 690, AC, DC, that one just doesn't matter.

C2 is a non-polarized audio capacitor. Considering where it is used - not a great choice but will work.

Need to fix solder joints at E3 and E4. This very well could be the source of the 9.9V versus 8V.
What part number is installed at CR7? Check part numbers on it as it may have been substituted.
Good solder joints at both anode and cathode of CR7?
If the diode is the right part - you should be measuring 7.79V to 8.61V.

HV is bad - still need voltage measured at E2. Voltage at E2 is what sets the output voltage and gives us a starting point on where to start looking.

Fuse F7 - is that your GI fuse? If so, that doesn't go to the power supply. You may have a shorted lamp or lamp socket somewhere. Did you bump a wire to a lamp socket within the light box?

#11 10 months ago

Awesome G-P-E amd ChrisHibler. Will take a while to wait out the arrival of the things I need. I want to do it right so anything that looks iffy to you I'll just redo.

Will update here soon as i can and drop this on the other thread. Sorry, it got away from me!

#12 10 months ago

Getting somewhere! I found my C1 replacement in the mailbox today. On it goes!

This has made everything real close.....but high.
With all the stuff above done, plus the new cap I read:

TP1 = 63.8v
TP2 = 46.5v
TP4 = 5.08v
TP5 = 9.92v

I am more excited about this development than a grown adult should be.

The question now is, how high is TOO high? And is there anything to be done about it?

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#13 10 months ago

TP1/2 are a little high probably because they are unloaded. Those are fine.

I’ve never seen TP5 (8V offset) that high but it shouldn’t cause an issue.


Chris Hibler - CARGPB #31
Http://chrishiblerpinball.com/contact
http://www.PinWiki.com/ - The new place for pinball repair info

#14 10 months ago

High voltages are now within tolerances.

But -

Quoted from G-P-E:

Need to fix solder joints at E3 and E4. This very well could be the source of the 9.9V versus 8V.
What part number is installed at CR7? Check part numbers on it as it may have been substituted.
Good solder joints at both anode and cathode of CR7?
If the diode is the right part - you should be measuring 7.79V to 8.61V.

8V supply still needs to be fixed - there is definitely something wrong with it. There are *only two* parts to that supply. One or both has an issue.

#15 10 months ago

The two parts that Ed is referring to are CR7, an 8.2V zener (1N4738), and R10, which should be changed out to a 680 ohm resistor. See image.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info
pasted_image (resized).png

#16 10 months ago

See ---
https://pinside.com/pinball/forum/topic/first-restoration-gottlieb-volcano#post-5988944
Look at post #14, photo #2.

CR7 -- in that photo, that should be 1N4738A or equivalent.
Yet when I look at the photo - I can make out the ending "0A".
If that is a 1N4740A then that explains why he sees 9.92V.
To make it right - replace CR7 with a 1N4738A.

#17 10 months ago
Quoted from G-P-E:

Yet when I look at the photo - I can make out the ending "0A".
If that is a 1N4740A then that explains why he sees 9.92V.

Excellent detective work.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#18 10 months ago

WOW G-P-E !

That is 100% my problem. I pulled it out and can get a good zoomed shot of the writing (no way can I read it with a naked eye!). The characters 740A are clearly visible on the barrel part (pictured).

Total genius. I mean, how did you get that!!!

Pretty PO'd with the supplier. I went back to make sure I ordered the right thing (also pictured!)

So I have ordered some of these:
https://au.mouser.com/ProductDetail/on-semiconductor/1n4738a/?qs=SSucg2PyLi78uHqjX5pYmg%3D%3D&countrycode=AU&currencycode=AUD

Different supplier, but another wait on shipping. I am learning that pinball repair requires patience

To be continued.....

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#19 10 months ago

Yesssss! I got lucky and found just the right part for CR7 at a local shop today. No waiting on the mail. Double checked the labelling and installed it.

The 8V TP now reads....... 8.3V !

Output pins all read as the diagrams tell me they should. I think I'm done!

Generous help here from everyone, but incredibly grateful to G-P-E and ChrisHibler especially.

Next, research and test the Driver board.

Will update my resto page, but if I run into more trouble I can't solve with other threads, I'll start a new one in the tech boards. I know what to do now.

__Still can't believe how you solved that Ed__

#20 10 months ago

I was looking at this thread since I am working on the same PSU from a 1983 Gottlieb Haunted House game. I noticed that your schematic (just like mine) shows R10 as 30 ohms and 2W, but the photo included earlier and some of the messages above indicate on your board it is 680 ohms and 1/4W. You seem to have this working, but I just wanted to point out the apparent discrepancy so you can make absolutely certain that you have the right part in there and don't have issues down the road. Good work and best of luck.

#21 10 months ago
Quoted from reshuman:

I was looking at this thread since I am working on the same PSU from a 1983 Gottlieb Haunted House game. I noticed that your schematic (just like mine) shows R10 as 30 ohms and 2W, but the photo included earlier and some of the messages above indicate on your board it is 680 ohms and 1/4W. You seem to have this working, but I just wanted to point out the apparent discrepancy so you can make absolutely certain that you have the right part in there and don't have issues down the road. Good work and best of luck.

The original Gottlieb design has been improved upon, many years ago, by replacing R10 with a 680 ohm resistor and CR7 with a 1N4738. This has been common practice for a long time now. It prevents CR7 from burning up.

Chris Hibler - CARGPB #31
Http://chrishiblerpinball.com/contact
http://www.PinWiki.com/ - The new place for pinball repair info

#22 10 months ago

Thanks much for taking the time to provide this explanation! By the way, I do see the A2 PSU PCB is slightly burnt under my CR7. I find it a bit surprising since the worst case current calculation thru R10 (30 ohms, 2W) should be about 0.2A (using worst cases:+10% for the nominal 12.4V, -5% for the 30 ohms, and -10% for the 8.2V zener) is 0.22A and the corresponding power dissipated by the diode would be 1.8W which is supposedly rated 2W.

#23 10 months ago

PS Hey Chris, out of curiosity why does the updated design call for replacing the CR7 1N3445 (8.2V, 2W zener diode) with the 1N4738 zener which appears to be for the exact same 8.2V? (Why couldn't you juts increase the resistance of R10 to reduce the current using the existing 2W zener?

#24 10 months ago

You can reuse the 1N3445 but in many cases, this diode is pretty badly burned and is hard to find.
If you replace the resistor then you can use the more common 1N4738A.

#25 10 months ago

Thanks GPE for the quick reply. Is this 8VDC source coming from PCB A2 only used as the center tap reference voltage for the 5VAC transformer output (so theoretically would never have any significant current going through it)? Is that why the R10 value can be increased so much (from 30 ohms to 680 ohms) in the revised design and therefore significantly reduce the current passing through the CR7 zener? If so, then the original Gottlieb designer used a much more expensive part (R10 30 ohm 2W resistor) for no reason. (Almost like they were trying to use as much of the 2W power rating as possible - for no reason.)

#26 10 months ago

This display offset voltage is a very low current. How low of current? I never measured. I am truly curious and plan to measure this in my System 80A machine... someday.

Gottlieb used the same basic displays and voltage regulation with the System 1.
The system 1 used 1N4738A/100 ohm resistor pair for the voltage regulation and it still appeared to be more than required.
The System 80 machines used the same displays, the 80A games used 7 digit displays but the current increase was negligible.
I think the original designers had no idea as to how much current would be required so they bumped it up to the max.

Minimum current required must meet the minimum knee current which is about 1mA. That part is easy.
Maximum current is determined by the resistor. If resistor value is too high, the resistor becomes the dominant factor in setting the voltage. I normally use 470 to 680 ohms. This resistor value is low enough the supply the minimum current for the zener and high enough to keep the resistor/zener cool. There is a max value to the resistor but I haven't hit it yet. The max value for the resistor is where the load current through the resistor becomes the driving factor in determining the voltage drop.

#27 10 months ago

Thanks again. The system I am working on is vintage 1983, so would likely be what you call an 80A. I will have to look and see if I can find a 60 ohm 2W resistor (and reduce the power to the zener by 50%) or a 100 ohm 2W (and reduce by 70%) in my parts cabinets.

#28 10 months ago

Aaargh! I've been at this for days since thinking I was done.

"Something" has happened to my 5v.

It variously:

- doesn't light the LED
- reads too low (4.5 ish)
- reads too high (6.2 ish)

And the trim pot does nothing to change it.

Haven't given up, but "rottendog" is definitely in my Google search history now...

Working through the advice offered here at the moment:

https://pinside.com/pinball/forum/topic/gottlieb-the-games-80a-no-5v-and-probably-more-problems#post-5722907

#29 10 months ago

This is indicative of a bad connection. Probably a bad solder joint, often at the legs of the power transistor on the hot plate.

I would look to others before the RD power. Those have several posts where the wrong parts were chosen/used on the boards resulting in burned parts.
Gulf most closely 'followed' my design, I would look into those.

#30 10 months ago

It's quite common to "lose" the connections at that big power transistor's "rivets" on the circuit board. A couple of jumper wires usually solve that problem.

#31 10 months ago

KenLayton So I went with your jumper wire idea. Not sure if I have done it in the same way you would. It's not pretty but it's working!

Screen Shot 2020-12-20 at 9.53.06 am (resized).png
#32 10 months ago
Quoted from KenLayton:

It's quite common to "lose" the connections at that big power transistor's "rivets" on the circuit board. A couple of jumper wires usually solve that problem.

Which is why I suggested the option of a Gulf board early on. Rebuilt a few of these boards and getting a good connection on the big transistor is tricky. I'm comfortable about doing it now but on your first rebuild odds of getting it on the first shot is doubtful.

Some reason the wire trick never occurred to me, have to file that one away.

Not knocking the OP, bit me on the posterior as well.

Hey there! Got a moment?

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