Hey All, hoping for a little help and a sanity check. I'm helping someone with their Lord of the Rings, and I've hit a snag. Before I go further, I wanted to see if someone could offer some advice.

History:
A while back he had a dead pop bumper and a stuck-on flasher. I did some testing, pulled his driver board, and found the associated transistors were bad. I know they're a little weak on this game, so it wasn't a huge surprise. Replaced the transistors, as well as the burned out pop coil, and he was good to go.

Fast forward a couple months and he texted saying his F21 kept blowing. He realized it happened every time the ball goes into the Orthanc VUK. I checked and the coil was toasted, coil sleeve partially melted. Pulled the board and the associated Q4 transistor was shorted.

Current Attempt (failure):
I replaced the Q4 transistor (using the recommended IRL540 'upgrade' over the original 20N10L), replaced the coil, and the fuse. The old coil looked like it had its diode snapped partially off, which may have been the problem.
I tested the new transistor and coil before and after install, seemed good. Fired the game up, but as soon as that coil was triggered the same thing happened: Fuse, Coil, and Transistor all blew.

So I'm at a loss for the moment. Normally a bad transistor / coil have been the culprit for me over the years with most games. Is this a possible chip issue? With 3 transistors and 2 coils getting killed in the past few months, could something be going? Could just be a coincidence. Thanks in advance for any advice/help. Not sure where to go next.

Additional note, the old VUK coil diode was snapped off on one side. I assumed maybe that's why it blew originally.

The guy who owns this game loves it to the point of playing hundreds of games a month. It gets played all the time, so hopefully with some help I can get him up and running soon!

Here's what I found when I pulled the original melted coil.

I actually did replace the coil, transistor, and fuse all at the same time. I tested the coil resistance before installing it, and it was in the low double digits (I forget the exact number at the moment, but 10-12 ohm range I think). The fried one was 1.5 ohms.

I'll double check the wiring to make sure I didn't install it backwards.

PXL_20210603_221827568 (resized).jpg

The Capacitor next (C267) to Q4 tests shorted at the moment. I noticed the same thing when the previous transistor was blown/shorted. As soon as I replaced the shorted transistor, the capacitor was fine, which makes sense. I did not fully test the resistor (it was not shorted though, I did check that).

Waiting for the guy to take a pic of the coil to verify the wiring.

Just got the pic of the coil from him, and it makes sense now. Diode was reversed on the replacement coil. I missed that detail, and wired it backwards it seems. Boom.

Thankfully, I have a spare coil, transistor, and plenty of fuses. I don't think anything else would be blown, right?

Yeah, I usually double-check, triple-check, and take pics. In this case I did the worst thing you could do: got all excited all the harder work was done, and rushed the final step.

Got back a bit ago. Everything is up and running well, and playing great. Didn't take long to pull the board, install the new transistor (again), and replace the coil (properly). He's thrilled to be flipping again. He easily puts hundreds of games on it a month, so I'm sure I'll get another call soon. He doesn't want to go LED all over, but he let me throw some warm whites in his lower GI, looks much better. A lot of bulbs were out too, ones he didn't notice, so the game looks a lot better.

I just need to convince him to start shopping it more. It needs new rubbers, a tear down and shop, etc. But that's for another time.

Thank you all! I appreciate the help. And Pin_Guy I don't mind hearing the explanation, I fill my brain with all sorts of info like that, it's fun.

Marking solved, much appreciated!

Yeah, they blew pretty much instantly as soon as the switch for that coil was triggered. I saw the fuse go bright and pop, and knew I likely goofed something up (or that something else was wrong).

So Pin_Guy you're saying that coil is still probably good, and I can just swap the diode?

phishrace I'll suggest the flipper coil swap, though he seems happy with the game as-is. Always good to have options!

Sidenote: I noticed his spinner doesn't seem to register much of anything points-wise. Been a while since I played LOTR, I assume that it should always score something, regardless of mode? I spun it when no mode was active and it didn't do anything. Thinking the switch might be bad? Just figured since you guys were here, I'd ask.