This one strikes me as strange...

So I'm working on this for a customer. The sound is pretty awful -- low and distorted. Also some of the sounds seem to be missing. The call outs work, but the music is missing in test.

Never worked specifically on a DE sound board, but I look up that it requires +5, +12 and -12. The board also needs -5 to work properly, but that's produced on the board itself.

I check the input voltages, and the -12 is missing. -12 comes from the power supply board by a black wire with a white stripe. Sure enough, the black-white wire on the Power supply board has no reading. Funny thing, the adjoining pin does read -14V. Hmmmm....

I pull the PSB and examine the connector. Notice anything strange?
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the thing is... it looks to be untouched. I mean, there is previous work on the PSB, but that connector looks to be factory. Yet, the -12 wire is on the key!

I was under the assumption the sound would not work at all without the -12

This machine has some strange previous work.

The Flipper coils were replaced. They were oriented correctly, but the sleeves were installed backwards. Maybe this is because the high-voltage fuse was blown, and the previous tech didn't know how these solid state flippers worked.

In the manual, I found the HV fuse value listed as both 3A and 5A. The blown one was 3, so I replaced with a 5.

I don't have an IDC punch tool, so I used a screwdriver to move the -12 wire to pin 2.

Sound is working good now. I guess the lessons are: always check voltages first, and don't be afraid to second guess previous work