I pulled a WPC driver board last week to replace a burned GI connector pin, pretty simple stuff. I hadn't had a reason to pull a WPC board in close to a decade, as my collection has slowly Stern-ified

Bottom line is I remember doing it several times back in the day, but aside from trying to get the board back in place through its nest of connectors I remember it being not a big deal.

I had forgotten the tidbit below:

http://techniek.flipperwinkel.nl/wpc/index2.htm
Exploding +20 volt Capacitor.
There are cases when the +20 volt capacitor (Driver board C11 on WPC-S and prior, C10 on WPC-95) can just explode. This happens when a shorted flipper coil diode or shorted transistor on the Fliptronics board causes the 70 volt coil power to feedback into the 20 volt flashlamp circuitry. Because of reverse voltage, this blows the 20 volt capacitor. Also installing one of the ribbon cable connectors in the backbox on the header pins (top row of header pins to bottom row of housing) can do the same thing. And lastly, if connector J124 is mistakenly plugged into the driver board connector J128 (they are keyed alike!), this can cause capacitor C11 to explode.

Basically, I was overconfident that they wouldn't have engineered something like that into the system.

I had the connectors labelled, I just wasn't being super careful.

Stuff worked initially, no explosions. So we test fired a game (a buddy was over) and I could hear a hissing noise... we look up and smoke is pouring out of the top of the game. Power down, open the game, start fans, open windows, etc... I haven't SEEN a cap go out out like that before.

I had a replacement on hand and thanks to others having documented this problem in the past I was back in business within an hour.

Consider this a PSA... and a personal reminder to myself that yes "it can happen to you" ..

Personally, I will make a big tag for that connector, and if nothing on that game plugs into J128 it would be tempting to just put a dummy connector housing (fixed in place with tape) or something on that connector....

Yikes, that's some horror show stuff. My largest fallout was having to drag the board out and then having to air out the room for a few days. I can't complain; heck I still had my soldering and desoldering equipment set up woo-hoo!

That other cable switch above sounds like it would be more intensive a fix; any idea how many chips it would take out (e.g. have you had personal experience with that one ? , or know anybody who has?).

I followed through with my labelling plans noted above, I am tempted to go back in and do the two you mention above as well...