Quoted from emsrph:Trying to digest the Bally Repair Procedure guide FO 560-3 to figure out how to proceed...already invested many hours into this and would like to cross the finish line.
The document talks about using an AID probe- is that similar to a logic probe?
Says erratic game operation may be caused by failed U19 or U20 (also U14 but I replaced that to cure the constant re-booting).
Also that flickering lights and solenoid issues could be caused by a fault on the BUS line that could be U17, U18, U19.
Any of that sound like the right track? How do I test those?
Attempting to teach myself but spinning my wheels. Appreciate any guidance with this.
I can't remember exactly, but I think people have had failure in the gates around VUA clock and etc used in triggering that caused odd operation and random lockups, so its possible. Maybe quench remembers as I think he posted in one of those threads. None the less you can check with a logic probe and step through all the gates around the VUA - Q2 area. I think that is what the 560-3 book is talking about.
If you replaced U14 make sure you use CD4049UB or MC14049UB. I have had trouble with TC4049B causing the zero cross detector to kick randomly making each zero position lamp on all four lamp board decoders flicker. UB or Unbuffered type being needed.
Can unplug the speech pass through stuff and go right to the lamp board to make sure the speech card is not introducing a problem with the lamp signals.