1981 Bally fathom solenoid issue

[DRD]

My fathom was blowing transistors on its old solenoid board, but the fault has been intermittent. I have replaced the blown power transistor/ diode/ resistor then all works well again for a while. I tried my paragon's alltek solenoid board in fathom. Fathom then fried one of the transistors on it. Naturally I was delighted at this point, but it was a easy fix.

So I wonder if the true cause of the fault lies elsewhere.

It goes for days at a time on the old board and works fine. It managed a day of league play with no problem on its old board. It then atomised a pair of resistors in the high voltage area and blew the high voltage fuse in the rectifier board.

I don't want to be dismantling one game to diagnose another so I bought an alltek solenoid driver board to help diagnose the troubles in fathom. With the new alltek board in and the high voltage fuse replaced, the game works fine

But when I run a solenoid test on fathom with the new alltek board the left pop bumper fires on three of the tests! It fires when it should (4). And also fires on 20 (coin lockout door) and 21 (flipper relay). Now 20 and 21 are low power coils that are basically energised constantly when you play the game.

Does anyone know what might be at fault please ?

Thanks

 

[Johnnyo]

https://pinside.com/pinball/forum/topic/pop-bumper-fires-with-flipper-activity

Not quite the same fault but related, lengthy post but in depth

 

[DRD]

Thanks for that. Looks like I am going to get an alltek MPU board that I can float between my games to help diagnose problems and eliminate things from my enquiries. I have swapped over original MPU boards before but changing roms and jumpers is a real faff and has risks that you will fry things and end up with two games down

when you read that pinside about what can cause these solenoid issues

Bad contacts on high voltage switches
Bad diodes anywhere in the game
Bad resistors
Dodgy switch in coin door ........

I guess you just keep your fingers crossed that it is an easy fix