(Topic ID: 298255)

Gottlieb System 1 4v and 8v Low / Dim Displays

By Knxwledge

71 days ago


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  • 17 posts
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  • Latest reply 69 days ago by Knxwledge
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#1 71 days ago

Weird problem on my Gottlieb System 1 power board. The previous owner had changed the filter cap but didnt do much else in the way of preventative maintence, so I did everything outlined on Pinrepair. Power supply seemed to be working befor my rebuild but I hadnt tested 4v/8v, displays were dim before my rebuild. On first go after rebuild I could hear sparking and saw little bit of smoke. I think this was caused by 2 bad solder joints I made. Fixed that.

Low 4v and 8v, might be affecting displays, all displays are dim. Both measure about 1vdc at A2p2 male pins.  -12v, 5v, 60v and 42v are good at A2p2 male pins.  Measuring A2-P1 connector, black lead on gnd and red lead on pin 1,2,4,5 all measured correct AC voltage as listed in schema.  Measuring pin 6,7 this way gave me half of what was expected, putting black lead on 6 and red lead on 7 gave me proper 69vac.

8v components (replaced by me already):
Cr21 1n4738
R21 100ohm  1/2 watt

4v components:
Cr22/cr23 1n4148

5vac components:
Cr1/cr2 1n5401 3a 100v (should be upgraded?)

Im going to pull the board back off and check all these components. Any other suggestions?

#2 71 days ago

Just checked all the components listed and they're fine

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#3 70 days ago

The amount of people on FB who told me to just buy a new board when I asked for help figuring out how to fix my original one makes my blood boil. When checking CR1/CR2 I did notice one of them had a bad solder joint. Not sure if that was from me grabbing it to lift one leg out of circuit, or if it was like that already. That could explain it, but I've ordered upgraded 400v 6a rectifier diodes off Ebay and am waiting for them to arrive. If it's not that, then I really don't know what it could be

#4 70 days ago

Just buy a new board!

#5 70 days ago
Quoted from G-P-E:

Just buy a new board!

Why does your business even exist when the answer is to always buy a new board? Fuck buying parts to fix things, I just want the path of least resistance!!!!!!!!

/s I love you Ed

#6 70 days ago

HECK YEAH!!!
Oh, wait, I no longer sell those boards... um... nevermind.

Seriously, though -- those 3A rectifiers could cause your issue but you said the +5V was working fine. That says the 3A rectifiers were fine. Bad solder joints can do amazing things, though.

Do make sure you are measuring the +4 and +8V while using the digital ground and not the high voltage ground.

#7 70 days ago
Quoted from G-P-E:

HECK YEAH!!!
Oh, wait, I no longer sell those boards... um... nevermind.
Seriously, though -- those 3A rectifiers could cause your issue but you said the +5V was working fine. That says the 3A rectifiers were fine. Bad solder joints can do amazing things, though.
Do make sure you are measuring the +4 and +8V while using the digital ground and not the high voltage ground.

Hmmmmm which ground is the digital ground? I was using the ground on the same connector as the voltages I was measuring because I wasn't getting accurate readings hooking up to the ground on the big filter cap. I think I'm doing it right. I was also gonna check for any bad solder joints on the transformer lugs but if the 5v is good I highly doubt it would be that.

#8 70 days ago

Yep, there's your problem.
Pin 5 of J3 is your high voltage ground, pins 4 & 5 of J2 are your low voltage (digital) ground.
Use the negative end of your 3300uF cap to measure this voltage.

Nobody knows why Gottlieb isolated the two grounds. Using the wrong ground for your meter's reference is known to cause voltage to measure incorrectly even though they are working.

#9 70 days ago
Quoted from G-P-E:

Yep, there's your problem.
Pin 5 of J3 is your high voltage ground, pins 4 & 5 of J2 are your low voltage (digital) ground.
Use the negative end of your 3300uF cap to measure this voltage.
Nobody knows why Gottlieb isolated the two grounds. Using the wrong ground for your meter's reference is known to cause voltage to measure incorrectly even though they are working.

Aw man what the hell?? What else should I be measuring from the filter cap ground then? Everything else seemed accurate
Okay then I will reassemble the power board and test it properly, forget the upgraded diodes. I was reading on Pinwiki that if the displays aren't used for a long time they can become dim, so that must be the reason they're dim. Previous owner didn't get it 100% working, and he bought it from an old lady who had it sitting in her garage for 30+ years, so it hasn't been used very much at all recently.

Edit: I'm assuming 42v and 60v ground are separated from 5v, -12v, 4v and 8v ground, which would explain why when I measured 5v and -12v from the ground at their respective connector, it worked, but the ground at the connector which has 42v, 60v, 4v and 8v is the high voltage ground only.

#10 70 days ago
Quoted from Knxwledge:

I was reading on Pinwiki that if the displays aren't used for a long time they can become dim, so that must be the reason they're dim.

That has happened with me on several occasions. You can do the "burn off" procedure or just keep the machine on overnight and see what you get.

#11 70 days ago
Quoted from newmantjn:

That has happened with me on several occasions. You can do the "burn off" procedure or just keep the machine on overnight and see what you get.

I will likely just leave it running while I'm in my garage working on other projects so I can keep an eye on it. Would be a good stress test on the power supply, but I don't feel comfortable leaving it on unattended just yet.

#12 70 days ago

That 4 and 8V using the 'other' ground catches a lot of people off guard. All the others look to have been measured properly. I'm surprised none of the FB guys mentioned this.

#13 70 days ago
Quoted from G-P-E:

That 4 and 8V using the 'other' ground catches a lot of people off guard. All the others look to have been measured properly. I'm surprised none of the FB guys mentioned this.

FB's a crap shoot, I always take advise given there with a grain of salt personally, unless it's from the well-known people like Chris Hibbler, Eugene Mosh or Jerry Clause. What would happen if I tied both grounds together? How are they "separated" exactly?

#14 70 days ago

If you look at the schematics - you will see there are two separate grounds on that board.
Nothing will happen if you tie the two grounds together. In fact, most (if not all) of the replacement boards have the two grounds purposely tied together to avoid this type of problem.

#15 70 days ago

Oh so the grounds come from the same place, but they are separated on the power board. I was thinking they were tied to 2 different places in the bottom of the cabinet. I think I will tie them together on the power board, I don't see a reason why not to, and it seems like the meta of working on Gottlieb solid states is redundant ground mods anyway . Imagine if I had bought a brand new board, I would be out $90 + money spent on replacement parts, and I wouldn't have learned anything. People who do that are doing themselves a big disservice IMO.

#16 69 days ago

Ok with the grounds tied together and the board back in the game, Im getting 3.68v for the 4v, and 8.6v for the 8v. Is the 4v acceptable?

#17 69 days ago

Ok red lead on ground lug, black lead on positive lug gave me 0.99 in diode test, ~0.4 with black lead on other lugs. This was the case for the 2 original bridge rectifiers and a replacement one I had on hand so Im guessing thats fine. Cr1 and cr2 were getting hot after the power supply was on for not longer than 5 minutes so I suspect those?

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