I have Shadow (WPC-S) that has been having some strange behanviour. Was working perfectly for months, and is now resetting on any double flipper press, and the coils associated with the fliptronics board are weak (magnet and flippers). I have quadruple checked all the standard flipper stuff, new mechs, new coils, no mechanical binding, but they are just weak - same with the magnet - it does not have power to throw the ball more than a few mm.

I can get rid of the reset by installing Rob Kahrs board, however the flippers and magnet remain weak constantly.

The thing that is strange (and since i have never seen this, leads me to believe it is the issue), is the 50V starts at 75V upon power up (normal), yet creeps up to around 100V. This would be over a period of around 2 minutes. I have checked with 3 different power driver boards as follows and compared it to an Indiana Jones:

All of the following had ONLY J101 and J102 plugged into power driver board

Power driver board 1 in Indy - Stable 75V
Then put Power Driver board 1 in shadow - crept up to 98V

Power driver board 2 in shadow - creeps up to 98V
Then put power driver board 2 in Indy 0 stable 75V

Just to check my sanity, grabbed power driver bard 3 (out of CFTBL that has been running fine for 12 months)
Power driver board 3 in shadow - creeps to 100V
Power driver board 3 in Indy - stable 75V
Power driver board back in creech - stable 75V

So, i also checked the AC voltages at J101, J102, and they are comparable - AC voltage on Shadow is 55.5V, it did fluctuate up or down 0.2V

So i am stumped as to why this would happen, there is 0.9 ohm between the earth pin of the power point plug and the headbox earth strap, so i assume everything is grounded fine. There is really only the thermistor, EMI filter, plugs and transformer that could be the issue.

I don't have any other machines that use that same transformer (has different plugs to most), so can't swap that - does anyone thing the thermistor or EMI filter is a likely culprit? I have reseated the plugs to and from the transformer 3 times, with no difference.

Yes, tried 2 fliptronics boards, both work fine in other games. Hence why i believe all the issues are somehow related to the creeping up 50V

Thanks for that.

Just checked resistance between pin on J102 and male plug that goes into transformer lead (on black/yellow that has the 50VAC), 0.2 ohm on one, 0.6 ohm on the other

Thanks heaps zaza really appreciate that. I tested R260, and it was open....what confuses me, is why the board tested fine in Indiana Jones, multiple times! Anyway, i replaced it with a 47k resistor (as per one of your posts), and now have a VERY stable 75V!!!!!!

So my assumption was wrong....the flippers and magnet are still weak. Upon testing the voltage, all other coils are running at 75V, whereas the flippers are at 65V, and when the machine went into a ball search (was testing during a game with the playfield slightly raised), i noticed the flipper voltage dropped off. So not sure if this is a connector, or fliptronics board issue (even though i had previously tried anther fliptronics board!)

I had a sparky mate over this arvo, and it was good to have another set of eyes to go through things logically.

We swapped more boards, and got some strange readings that were always consistent on each board - voltage coming out of fliptronics was 65V one minute, then 75V the next. We did watch voltage at the coils, and whenever another coil would fire, the voltage at any other coil would drop. We then started testing the AC voltage at J105 (this takes AC power to the fliptronics board) and noticed it seemed to fluctuate, and it would drop when the coil voltage coming from the fliptronics board dropped to 65V instead of 75V, yet pull the plug off J105, and the pins had a solid 50VAC. Even with the plug in at J105, and not plugged into the fliptronics board, we would get variable voltage at J105. Visually, there is a faint burn mark on the plug, so the assumption is there is/was a small short there (wires looked good, and there was continuity from one end to the other) that would manifest itself under load - causing the weak flippers and magnet driven from the fliptronics board. So i made up a complete new cable with new plugs, and NOW IT WORKS perfectly!! Also, i removed the Rob Kahr reset board, and resets are no longer an issue.

Definitely one of the more challenging repairs i have done!