The mystery: A Bally Lost World has no general illumination lights on the playfield. Coin door and backbox GI are working. 6.8 VAC is measured at rectifier board J1 pins 1,2,5, and 8. 6.8 VAC is measured at every single socket. GI bulbs in the playfield have been switched out with known working bulbs. Sockets have been cleaned. Continuity checked between transformer and all sockets, GI pins on rectifier board, and ground straps. Fuse is good.

J1-2 to 5 GI circuit worked. J1-1 to 10 circuit worked intermittently. Headers were reflowed and trifurcons installed. Now, nothing except 6.8 VAC and no lights.

Can you solve this mystery? I can't after about 4 hours of testing.

MMGB I think you are on to something with J1-1 &2 not grounding. I hooked the J1-1&8 GI Bus and Return to the J3-2&11 GI Backbox GI Bus and Return and the correct half of the playfield GI lit up. I also measured voltage on backbox return and it is 300 mVAC which makes sense. The playfield GI return shouldn't be 6.8 VAC. I also measured the return side of each of the backbox sockets which measure 300 mVAC. The playfield shouldn't be measuring 6.8 VAC across each socket.

I triple check the solder joints on the back of the rectifier board and everything looks fine. I reflowed them again. No change. What could I possibly be missing?

tomtest I unplugged J1 and jumped the backbox GI Bus and return to J1-1&8 and the playfield GI lights came on. That would mean the problem is on the rectifier board, right?

Picture of back of rectifier board for reference.

PXL_20211230_193245792 (resized).jpg

tomtest MMGB turns out the ground to playfield return is on the front side of the board under the plastic that holds the pins. I let some solder seep through and it finally grounded. When I turned on the game all playfield GI lit up, but no playfield lights are on. I checked voltage at TP1 - nothing. The fuse blew.

I did some tests and noticed that I have continuity between J1-7&8. I looked at the schematic, and it doesn't look like that should be happening. I looked all over the front and back of the rectifier board, and I don't see any splashed solder.

I removed the male pins from J1 to check the front side for a short and don't see anything. Any help is appreciated. Before I put the male headers back in, should J1-7&8 have continuity? Is that what is causing the new problem? This has been the most frustrating rectifier board I have ever dealt with.

Interesting development: my DMM reads continuity up to 30 ohms resistance. It was reading through the 25 ohm resistor that connects the 5v circuit to ground. Therefore, the 7v circuit was showing continuity with the 5v circuit because they were both grounding. I found this out by testing resistance at varying points to try and figure out where the short was. Turns out there wasn't a short. Put everything back together and all lights are working perfectly. I'm not certain why or how the 5v circuit fuse blew, but it is fine now.

Thank you MMGB tomtest and JethroP for your help and suggestions.