Williams Power Supply & Transformer Information

A relatively frequent issue with Williams linear power supplies is a portion of the AC power plug burning up. It happens at the 22.6V AC section of the plug due to the amount of current draw that’s pulled from here. This is the voltage that powers BR1 on the power supply, which produces unregulated +/-12V, and is also the source voltage for the regulated +5V that’s created at the 6057/6059 transistor.

This modification applies to all games of the Defender and Stargate-Sinistar period. Some Sinistar uprights apparently received this treatment from the factory, so Williams knew it was a problem and probably fixed it on all future games.

You’re adding additional wires to create pairs for the 22.6V and 22.6V center tap wiring to effectively split the load. Pins 2, 4, and 6 at the AC header are unused duplicates of 1, 3, and 5, resulting in pairs 1/2, 3/4, and 5/6. Running dual wire pairs instead of single wires will make it able to handle the current draw better and thus eliminate the plug burning up again in the future. I strongly encourage replacing pins 1, 3, and 5 with new trifurcon pins too.

Your wiring pairs will be crimped at the plug end and the respective pairs will be soldered together at the transformer tabs.

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