Hey guys, I'm trying to trace a problem with my STTNG, and I'm wondering if anyone else has seen something similar. First, the left cannon started coming up with "can't find home" errors, but the switches would work fine in the tests (home and mark). It's done this intermittently since I got the game a couple of months ago, but usually only after it's been on for a long time, so I thought it was just the cannon wiring loom being worn out. Plan was to just replace these eventually... Then I ran through some other tests, and noticed that the two underplayfield diverters and the drop target weren't firing either. I checked, and the bottom diverter (that goes to the left cannon) had a coil that was completely melted somehow. Now, I know that this worked at one point (since balls would go to the left cannon), so something went very wrong at some point. I did check, and both sides of those coils show continuity to ground, so I think this means I have a short somewhere-any thoughts on how to track it down?

Also, something else that was very strange-I noticed that F103 was blown, so I replaced it, and then it blew again after I turned the game on. The weird thing is, this fuse is supposed to control a bunch of flashlamps (the ones in the borg ship), but those all work just fine. The coils that aren't working are on F105, which is fine.

Anyway, thanks for the help, but as you can tell this is the first time I've had to trace an issue like this.

Ok, some more progress. Reading up on this a little more, it sounds like this is a common problem with a 50v tieback from the drop target. That looks to be OK though, but it also appears that something else broken in that chain can cause these issues. Anyway, replaced the burnt out coil and checked the resistance on both diverters, and both of them are good. The circuit still seems to have continuity to ground though, and that only goes away when I disconnect the WPC8 board. I'm starting to think this is the problem, but it looks like someone else has "fixed" this board in the past, since there are some extra wires/solder jumping things on the back. The Q16 transistor is loose, so I think the next step might be replacing that. Is there anything else that I should try checking on the main driver board, or is the WPC8 completely isolated?

I suppose that worst case, there's a rottendog replacement that I can get for this board, but I'd like to try repairing it first. Cheaper, and a good chance to learn on a board that has a cheaper replacement than a full on driver board.

Right, this is starting to get frustrating...

Tried the board repair, which literally went up in smoke. Ended up deciding to go with the replacement board, which I got yesterday. I replaced the burnt coil, put in the new board, and nothing... So, here's what I know now:

-Both diverter coils (the AE-25-1000s) are good (brand new)
-F103 blows right away when I turn the game on
-I have continuity to ground from both lugs of both diverters
-Somehow, I have continuity to ground from pin 2 of J104 on the 8-driver board, which is the pin that drives the upper diverter. This is with all the connectors OFF the board, and the board mounted in the backbox. There's nothing behind the board-just the standard metal spacers that all the boards screw into.

I obviously have a short somewhere, but I have no idea where or how to find it. The fact that F103 blows is a good sign (I suppose) because it means that something more expensive is not getting toasted along the way. Any other suggestions?

Learning more here, but still no closer to a solution. Turned out that there was a bad diode on one of the new coils. Replaced that, and replaced the TIP102 on the brand new board, and verified that the board transistors were OK, and that the coils were OK. Power up with everything disonnected-board is still OK. Power up with the CPU disconnected and the PF connectors connected-coils locked on. Turned the game off right away. If I turn it on again-nothing happens (fuses are good, transistor Q16 is not...again...).

The thing is, have 75v on the J4-1 (tieback diode voltage) that tends to be the problem on this game. Could that still be the issue?