User:Scott Hively/pinball/black knight/bk electronics

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First thing to note is this machine was manufactured in 1981. With age, electrolytic capacitors dry out, plastic connector housings become brittle due to heat / UV / age and electrical contacts oxidize.

And while Williams was innovative in pinball game design, their electrical designs are a bit suspect in a few areas.

Power Supply

These original power supplies are very inefficient. They generate a lot of heat.
With sketchy connectors and dried-out capacitors, this thing is generating some noisy and out-of-spec voltages.
I have decided to replace the board with a modern after-market replacement. I will rebuild the original and have it as a backup or sell it.

Original BK PS, installed
Original BK PS, removed

This is the original power supply. Just look at that heatsink on the voltage regulator!

Notice the darkened connectors. If Williams needed more current than a connector could handle, they would use multiple pins. This works great for a while until one of the pins has a bad connection, then the others heat up and they begin to fail. Vicious cycle.

The fuse holder in the lower-right corner was badly corroded. The fuse holder would make bad contact, get hot, and de-solder itself from the board. I installed an off-board fuse holder. That's the grey wire you see coming off the board.

Also, the 2-pin connector at the bottom-right had the yellow/black wire soldered to the back. This wire is then wire-nutted to the original wires. This was how I found it when I bought it. I'm assuming the male connector on the wires got toasty so someone just soldered wires to the board.

New connector

Here's the new connector compared to the old one.

New power supply installed

And here's the new one, installed and powered. Sexy!
LEDs behind the fuses and by the voltage test points are sooooooooooooooo nice.
You can see the new 2-pin connector on the right, and the new 12-pin on bottom.
I did not replace the GI (general illumination) connector even though it looks burnt. I have replaced all the old incandescent #44 bulbs with LEDs. The connector is still making good contact and now only caries a fraction of the current. It'll live.