http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Game_resets

Read and follow this, it's the grail on wpc resets.

http://www.kahr.us/

Above sells a "fix" board that is a work around, doesn't fix the issue, but will stop resets. Eventually whatever is causing the voltage drop may fail, but this definitely works for a cheap fast fix.

This is caused by the failure of a bunch of components (mostly connectors and capacitors) spread all through the machine. You can sort it out in many cases by replacing three caps - the main smoothing cap, the smaller post-regulator cap, and the input cap on the MPU board. I forget the IDs of these right now, but can look them up. I find that in many cases that's enough, but it's not a full solution. I'm not 100% happy with the daughterboard solution either - it should have much the same effect as replacing those caps, but with the downside of being expensive, and loading down a another PSU rail that isn't intended to do that. I guess it'd work OK, but it just feels like a *wrong* solution...

(Note - other things can go wrong to cause this too, e.g. half of the bridge rectifier failing, but that seems relatively less common)

In my opinion, use this solution now. No unscrewing to do, or extra troubleshooting. Should the problem resurface, then you can go to the effort and extra cost to fix it the other way. That's what I did when my stng started resetting one day. Back up and running the day the power module arrived and hasn't glitched since.

Reseating J101, J102, J114 (on the driver board) and J210 (on the MPU board) normally does the trick for me.

Edit: Usually is a temporary fix though. If it runs a long time without issues, likely will need to repin some of these connectors and resolder the male pins on the driver board.

You could fix a row of WPC games for the cost of one Kahr board. More convenient sure but checking voltages, reflowing solder, repinning connectors, removing z connectors, and only potentially replacing caps/BRs is real cheap.

depends what your time is worth.

Heh, I fully agree! It doesn't take me long to do this these days.

Heh, I fully agree! If I really had no time, and just needed a machine up and running, I'd consider using one of those boards. But I'd feel guilty about it, and I'd pull it out again ASAP and do the proper fix.

So... it's a matter of perspective. For me, the 'correct' solution is making the machine work as it was intended (with a couple of minor quality and component choice improvements thrown in, perhaps). Plus, there are a number of issues with the approach that board takes - I really don't approve. But I'm not going to nit-pick, if someone wants to take that path, and it solves their problem, all good.

The daughter board works great and it is only $30. It moves the cpu off of the overtaxed 5v to the under utilized 12v. In some ways, it should have been done this way to begin with. My time is worth a lot these days, enough to not spend 3 hours chasing down a reset issue. Someday when I have more time I can fix the issue, but the game will play perfectly until then. Every collector should have one of these on hand for the game that only resets during a pinball party too.