(Topic ID: 224176)

Gottlieb System 1 Driver Board- Locked Coil

By tengle93

1 year ago

Topic Stats

  • 4 posts
  • 3 Pinsiders participating
  • Latest reply 1 year ago by DropTarget
  • No one calls this topic a favorite


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#1 1 year ago

Working on a #JokerPoker restore and I'm about 98% done. Have one last issue that's driving me crazy.

What I have done....
-Have done all ground mods
-power supply tests perfect (original with upgraded 6800 ohm cap)
-fixed remote transistor problem (Kings bank)
-game powers up and plays


The Aces Drop Target bank coil is locked on and blows a fuse. I replaced the driver board transistors (both) and still have the issue. Removed the cable from the MPU board and still have 22V at the fuse (under playfield) so I know that the MPU isn't the issue. I checked for shorts, didn't see anything. Resistors check OK. Coil and diode check OK.

Could I just have a bad transistor(s)? Any other ideas?

Of course I could get a replacement board but not even sure that's the problem and didn't want to pay for that when the board seems ok except for the one issue.

Thanks in advance for any help.

#2 1 year ago

Isnt the aces the underfield transistor? Been so long since I restored mine. In a pinch, if it is, a tip 36 will work just fine.

#3 1 year ago
Quoted from maddog14:

Isnt the aces the underfield transistor? Been so long since I restored mine. In a pinch, if it is, a tip 36 will work just fine.

The Kings bank is the underfield transistor. Aces bank has the U45 transistor controlling the larger transistor all on the board. Those are both changed, but something is still pulling it to ground.

The only thing is possibly the 74175 TTL chip being bad but it seems to check the same as the rest of them.

5 months later
#4 1 year ago

Any luck?
I'm having the same issue on a Count-Down. Even with new CPU

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