Trying to clarify my 5 year old post as I have been asked a few questions about this common CV neon fix.
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U3 and U4 are on the Power Driver Board A-20028 in the WPC-95 schematic manual. U3 is a ULN2803A an octal Darlington Transistor array and U4 is a 74LS374 which is an octal D-type 3-state flip-flop (latch).
Here are photos of my repaired board (see the two sockets) and the schematic section that shows the two parts. I replaced U3 first and then U4 when that didn't fix the problem. Troubleshooting between them wasn't easy as the bad circuit in U4 pulled down the Darlington pair in U3 which made it look like it was bad.
I would advise you to buy sockets and ICs for both. Just be sure not to damage the PCB when desoldering. Practice first on a scrap board if you need to learn. I bought a Hakko desoldering tool which really makes removing ICs easy with little to no PCB damage. They are expensive but so is outside board repair and a damaged board.
Board_repair_U3-U4 (resized).jpgPartial_Schematic_U3-U4_fix (resized).jpg