Hello everyone,

I've been in the process of following Vid1900's "Bulletproofing a Williams System 7" topic and have run into an issue with my control lights. Per Vid's instructions I removed the TIP42 transistors on the driver board and replace them with IRF9640 (I know this is not the IRF he recommended), but it was what I accidentally installed..... yep I accidentally soldered 8 of these to the driver board..... (long story short, there was a mix-up I what was shipped to me). I've looked through the specs and I believe the 9640s will work ok, but I'm not 100% sure. After installing these Mosfets I jumped the gap where the old barrel resistors were, the ones that like to burn the board, again per Vid's instructions.

After that the playfield control lights worked for about a game and then stopped. Now none of the playfield control lights work at all. All GI lights work and I have checked the lamp fuse by removing it, testing it and then reseating it. I have also checked the voltage coming from the power supply board and it is registering at 16v. I also have 16v coming out of the lamp column drive pins.

However, I do not have any voltage at the lamp row drive pins..... should I? I'm a little fuzzy on how the lamps work as it relates to the columns and rows. How can I test or what should I look for as it relates to the lamp row pins?

Any help would be appreciated.

Edit - So I just reseated both the lamp column and row connectors and the lights worked again..... for 1 game and now nothing again. So would it seem to make sense that it would be in the connector or a broken circuit on the board? Would a connector cause all of the lights to stop working? Seems like it may cause some, but not all.

The connectors or solder joints would make all of the lights go out? I would imagine a row or column, but all of them? I mean unless all of the solder joints / connectors were defected. Thoughts?

Further information. If I check the voltage at the light sockets they are running approximately 16v. I'm doing this by grounding the negative from my mm to the ground case wire and then checking the red leads. I also checked the yellow leads and they are also registering 16v. Is this correct? I would think one would be positive and one negative, or is that where the diode come into play?

Even further information..... I turned the game on last night and the lights worked again for about 1/2 game and then quit. I'm going to continue forward with replacing the 40 pin connector between the MPU and Driver boards, fireproofing the power supply and replacing a few of the older capacitors on the power board. I'll let you know if any of these resolve the issue.

Bump.

Also further information. I finished replacing the 40 pin connector between the MPU and Driver board. I also found 2 caps that were bad on the PW board, so these have been replaced. Again, the lights seem to be intermittent, they may work for a game or two and then fade out and stop working. Any additional thoughts?