(Topic ID: 294700)

Help me find the last(?) gremlin in my friends Black Hole

By Jahkub

10 days ago


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  • 13 posts
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  • Latest reply 9 days ago by Jahkub
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#1 10 days ago

I'm just hoping someone has run across this before, maybe my search terms were bad but I haven't found anything quite like this issue.

The symptom: During play, the sound will quickly fade out over ~2 seconds and at the same time all solenoids lose power. After a variable but usually short time, say 20-45 seconds, the sound and solenoid power returns with the current game still in progress. It generally happens after a couple minutes of play. Lamps and score displays remain unaffected. He hasn't had it happen when on the lower PF, but he doesn't spend much time down there so I can't rule it out. The only other oddity reported is that the shoot again light remains on for the entire game after being lit, it awards the extra ball and just stays on until another game is started. Probably not related, but odd considering the new boards.

Work done on his game:
Ground mods to all backbox boards
All electrolytic caps replaced top and bottom
Aftermarket MPU, Driver, and Power board (I can't remember the brands ATM)
Extra grounds added on the connector between the MPU and Driver
Pull up resistors added to lower PF transistors
Edge connections on old boards cleaned with eraser (no crimps replaced)
New bridge rectifiers
All LED except chase lamps
All grounds tied together before the ground plate in the cabinet
That's all I can think of at the moment.

I'm really hoping someone has seen this behavior before and can point me in the right direction.

Thanks!

#2 9 days ago

Have you repinned any of the connectors? I would at least do the .156" power connectors, the J5/J6 on the MPU and both sides of the interconnect harness.

#3 9 days ago
Quoted from Knxwledge:

Have you repinned any of the connectors? I would at least do the .156" power connectors, the J5/J6 on the MPU and both sides of the interconnect harness.

This is key. The crimps get tarnished (or corroded if the battery leaked) and can cause all sorts of problems.

ALSO: there are 3 relays under the playfield. All coil power goes through a normally closed switch on T and and normally open switch on Q. You should clean and adjust those to make sure the solenoid power switches aren't the problem.

Finally: the sound card uses coil power for the amplifier (don't quote me on this see pinwiki: https://www.pinwiki.com/wiki/index.php?title=Gottlieb_System_80#Sound.2FSpeech_Power_Supply_Board_LED.27s , https://www.pinwiki.com/wiki/index.php?title=Gottlieb_System_80#The_Long_and_Winding_Road_of_the_Sound_Signals). so 1 theory is the solenoid power is cutting out and then returning after something cools down. Next time it does it pop the backbox open and test this voltage on the power supply, the coils and the sound board aux power supply.

#4 9 days ago
Quoted from Cheddar:

This is key. The crimps get tarnished (or corroded if the battery leaked) and can cause all sorts of problems.
ALSO: there are 3 relays under the playfield. All coil power goes through a normally closed switch on T and and normally open switch on Q. You should clean and adjust those to make sure the solenoid power switches aren't the problem.

I would think it could be a problem with the relays, except for his sound going out at the same time which sounds like the coil power is being lost further back someplace.

So the 'shoot again' light stays on as the game continues, and the light (or both lights, one on backglass too) stays on even at 'game over' status?

#5 9 days ago
Quoted from Knxwledge:

Have you repinned any of the connectors? I would at least do the .156" power connectors, the J5/J6 on the MPU and both sides of the interconnect harness.

I think I did put new crimps on those connectors but I'll double check next time I'm there.

Quoted from Cheddar:

so 1 theory is the solenoid power is cutting out and then returning after something cools down. Next time it does it pop the backbox open and test this voltage on the power supply, the coils and the sound board aux power supply.

I had tested the aux power board and was missing some of the voltages during the problem, although I can't remember exactly which as it was some weeks ago.
As best I can tell, the main power to the aux board comes from the 24vDC bridge, the 12vDC bridge, and the 12vAC from the transformer. So no real connection to the 38vDC power there. Although I see now that the 24vDC powers the T, Q, and U relays. So something is likely pulling down the 24vDC line?

Quoted from frenchmarky:

So the 'shoot again' light stays on as the game continues, and the light (or both lights, one on backglass too) stays on even at 'game over' status?

I can't confirm that the backglass lamp is also on, but yes, it stays on into the game over status.

#6 9 days ago

So at this point my idea is to inspect this circuit on the aux power board, along with the connections leading to it.gdfgs (resized).png

I'm all ears for more thoughts though.

#7 9 days ago

You said you repinned but didn't do any recrimps. That's only half the job

#8 9 days ago
Quoted from Cheddar:

You said you repinned but didn't do any recrimps. That's only half the job

I think I did put new crimps on the power board connectors as that was the only new board I installed. So new board, I accidentally said re-pinned above, I'll edit the post.

#9 9 days ago
Quoted from Jahkub:

I think I did put new crimps on the power board connectors as that was the only new board I installed. So new board, I accidentally said re-pinned above, I'll edit the post.

The other boards were replaced for a reason. It's likely they put the new boards in, nothing worked and they gave up. The switch connectors J5 & J6 and the interconnect should be done too but the playfield switch connector J6 is a common cause of problems as it's in the battery damage zone

#10 9 days ago
Quoted from Jahkub:

So at this point my idea is to inspect this circuit on the aux power board, along with the connections leading to it.[quoted image]I'm all ears for more thoughts though.

That aux power board only supplies power to the sound/speech board so even if its connector was pulled the coils in the game would still work.

#11 9 days ago
Quoted from frenchmarky:

That aux power board only supplies power to the sound/speech board so even if its connector was pulled the coils in the game would still work.

This could be used to eliminate this board. Pull the connector and if it still happens then it's not the problem

#12 9 days ago

You replaced the bridge rectifiers but maybe the 24V DC one down in the cabinet is going bad or has a connection issue? That 24v goes to the sound/speech aux power board, the knocker and the playfield coils. And you don't seem to be having problems with anything else in the game except those.

#13 9 days ago

I really appreciate all the responses! I'll set up a time with my friend to dig in further soon.

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