Bally Creature from the Black Lagoon (Bally, 1992) goes haywire intermittently

[Brucer]

Hi, I have acquired a Bally "Creature from Black Lagoon" machine and have successfully serviced the play field replacing lamps, rubbers, flippers, etc. The machine has been working well for some months but has now developed an intermittent fault which I am seeking help to solve...

After playing a few minutes, suddenly the flippers start firing randomly on their own and no longer respond to the buttons. The game cannot be played in this state. Usually this resolves itself after a while but returns periodically.

Any suggestions on what may be the problem or how best to troubleshoot will be much appreciated.

Thankyou!

 

[pinballdaveh]

i think the problem is in the fliptronics board. with machine off, unplug board connectors, unscrew and remove fliptronics board. check for cracked solder connections, solder if needed.replace and reconnect board. this problem could also be data related, so replacement of the cpu to fliptronics ribbon cable may be needed.

 

[Brucer]

Thanks pinballdaveh for the reply.
After posting the question I found a whole bunch of great info, especially this http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Check_fuses_F114_and_F115_message

Yes.. I forgot to mention I sometimes get the "check F114, F115" message. Turn outs LED1 went out during the failure which made it fairly easy to troubleshoot from there. However strangely enough even after replacing the 7812 REG Q2, capacitor C2 (showing visible signs of leakage) and checking diodes I was still not getting 12V at TP3 despite getting 18V at TP8 and LED6 being lit.
I had 12V coming out of Q2 but nothing either side of fuse F115. There is nothing but circuit board track between these two points yet I could see no visible break, so I decided to solder a wire bridge between the output of Q2 and the + side of C2. This worked!
I can only conclude that the link from one side of the PCB to the other at either Q2 or C2 had broken. Whether this was the original fault, or one I had introduced while replacing other parts I don't know, but it's working now so all good!

 

[pinballdaveh]

when radial capacitors leak, the oil inside leaks down the leads into the thru hole connector, stopping at the solder side. this oil corrodes the thru hole metal , breaking the internal connection. when replacing these radial lead capacitors ,trace repair or jumpers might be needed.

 

[Brucer]

I thought it might be something like that. My other theory was I might have damaged the thru-joint when replacing the cap. Maybe a combination of the two as the fault went from intermittent to hard at about the same time.