Repair Logs

Defender (Williams) Power Supply repairs

05/29/2000

Tools: soldering iron, solder wick, multi-meter

Problem: +12 LED out, no +12VDC

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Solutions: Diode bridge BR3 was bad, replaced with an equivalent 1.0A, 50V part from Radio-Shack

07/20/2000

Tools: soldering iron, solder wick, multi-meter

Problem: +5 LED out, no +5VDC

Looking at the schematics, I found there was 31.4 VAC coming in on pins 3 & 4 of 4J1. This goes through a fuse to BR1 pin 2. I checked pin 2 and there was 31.4 VAC present, Moving to the next component, C3, there was still around 31 VAC present, same with both D2, D3 diodes and the positive side of C2. But after C2, the voltage should be around 27.4 VDC and it wasn't present. I removed C2 and installed a new cap. This fixed the problem.

Solutions: replaced bad 47uF 50V electrolytic cap at C2