Next job was to rebuild the hacked power transformer board, replacing all of the bridges and the diodes for the high voltage display supply, as well as replacing the pin headers. I ended up running out of the correct length headers and had to ‘make do’ with what I had on hand, hence the gap in the top left connector on the board in the 2nd pic. But hey, its my own machine and not a clients pin and I wanted to see this thing up and running without having to buy anything yet if possible! I added heatsinks to the bridges, the larger two were cut up pieces of a larger heatsink from a dead plasma TV panel driver board that I had raided from my ex boss.
2nd pic is the finished board still sitting on my bench.
After that was done I started on the solenoid driver board, replacing the cap for the 5 volt regulator circuit, doing the ground mods as per Clays repair guides, and rebuilding the dead HV display regulator section, I replaced all of the transistors and diodes, I didn’t have a 2n3584 for the regulator transistor so I used a BUX85 initially.. then replaced it later on with a BUX84 (more on this in a moment). It seems I must’ve bought a bad lot of BUX85 transistors as every single one I have used in a Bally HV section so far has failed!.. these were ones I bought from WES components and they just weren’t lasting long.. I mean about half an hour and they would fail (they are higher voltage versions of a BUX84). I’m now using BUX84s I buy from Element14 and haven’t had a problem since.
I had already repaired some of the displays when I originally bought the game, replacing display glasses in three of them as well as some transistors and all the 100k resistors that often fail.
Next I started on the MPU board.. it wasn’t too bad as far as corrosion goes, but on powering it up it only came on with the LED stuck on.. I unplugged all the connectors leaving only J4 in, incase one of the other boards was locking it up, still no go. I knew the reset circuit was working as I checked it with a logic probe. Next I thought id try reseating chips, and when I got to the game ROMS.. about a third of the pins broke off of U2.
Shows over for the MPU for the moment, I have a new EPROM coming from Ken (skybeaux) he is doing one that combines the two ROMs into one, that plugs into the U2 socket.
