New issue. Everything worked fine until I removed the right side head wood panel for rework. It had been held in place by drywall screws. Repaired the panel separately while the head was in the horizontal position resting on foam. When I reattached the repaired panel and re-fastened everything, I now only get playfield and backboard GI. No sounds except occasional growling. Only one of the 3 MPU leds (+5V) is lit when power is on. Here are my test point readings at the power supply board using wire braid as ground. (Board is a Rottendog 2016 replacement WDP011C rev 3.)

TP +5V = 5.11
TP -12V = -13.93
TP +12V = 11.85

I checked every cable, connector, found no visible problems or damage. Checked all fuses. Reseated all connectors between the display board and MPU. Could the display board have been shorted during the work? (I did not remove or work on anything inside the head.) I've included photos. Maybe someone will see something I don't. Yikes, what have I done? Where should I go from here? Thanks!

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Thanks for your reply. Your suggestions make a lot of sense, and they're easy enough to do, although my 8-year EM experience is worthless in identifying which chips are which (unless they're labeled). So, I'll just re-seat the chips that are mounted in sockets and post results.

I first tried pressing down on all the chips on the MPU but no effect. Then I saw your post of the four highlighted chips. This morning I removed each one, gently cleaned the leg pins with a soft brass brush and re-inserted them into their sockets. I turned the power back on, and bingo! Everything’s back to normal. You were right. I’m not sure which one(s) did the trick, but my suspicions are with the two L6 roms because that’s what a previous error code showed. I played a few games and it plays perfectly. Thanks again!

I assume that would mean socket replacement?

The hum on this pin is back again louder and more annoying than before. From all that I have read on this forum about this unique Jokerz issue, here is what I will be doing, one fix at a time. The WMS service bulletin hum fix to the sound board does not appear to have been done, so that’s first, although I haven’t seen any claims that it actually solved the issue. Second, I am replacing/rebuilding the emi line conditioner and It’s MOV with new. Third, I’m replacing BR1, 2 and 3 bridges in the power supply boards. If that doesn’t fix it, I will try adding a 68 ohm resistor between the 2 head speakers. Lastly, I’m replacing the volume pot. And I bought a bog assorted ferrite core snap rings to try out on various cables and wires. If any of these actually work, I’ll open a new post and document the results. If none of this works, I’m out of ideas. Feel free to share any thoughts. Parts will be here early next week. Thanks.

Wow, you just triggered a decades long memory from tech school about pots and how carbon crystals can form on the wear surfaces from not being used for a long time. Thanks for the memory jog!

As far as the power supply board, it's a new (2016) Rottendog replacement and the 5 caps look it. I doubt you're recommending replacing them? But what about the aux power supply board? That's original and has 4 axial and 2 linear caps. I think I can handle that one if you think it's worth it.

Where would the sound section be? And the C30 - is that the big fat mama cap at the lower right?

Ah, ok. I misunderstood when you said sound section of the mpu. You meant the audio board as it’s called in the manual. Could you also clarify two other terms please: MPU and CPU. I thought they were interchangeable but the manual only lists CPU, the largest board in the back box. Are they the same? Still learning. Thanks.

Thanks so much for taking the time to clarify all this. I’ve been living in that manual, but it’s real work to decipher the blurry text. Much of the component text on the board diagrams is illegible. I printed mine from the file entitled “clean pdf”. It would be great if there was an original electronic file that would allow the reader to zoom in on the finer details. Of course, I shouldn’t complain: it was a free download, so I got what I paid for. Much better than nothing, tho.

IPDB says Diner is system 11C. Maybe they’re similar enough, but to be safe I checked earthshaker which is 11B: that machine’s CPU diagram was clear enough to read the cap numbers. Thanks big time for that tip: in my Jokerz manual they were unreadable. Want a good laugh? At first I started to panic when I couldn’t locate the sound section on my machine’s CPU in the back box. Then it dawned on me the damn thing’s mounted upside down! I wonder if WMS designers did that as a joke to trip up novices from screwing around where they shouldn’t be. Pinside forums — or even the public internet — weren’t around then to help out. Heheheh.