Williams Power Supply Repair

Robotron Jon

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First LED is not lit - No 5v.

I just rebuilt it with a Bob Roberts kit and the first light is still not on. I did not install one piece of the kit which is transistor 2N3055.

Visually all the fuses look good (haven't checked those yet).

Resoldered some pins that looked like they might be cold. The connectors look a little burnt.

Hmmm...
 
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Reflow all the pins on the 4 connectors and test all the fuses for continuity on the back of the board.
 
The power supply schematic in the Robotron & later manuals gives voltages that can be useful as clues to what is wrong.

And as 80s said, don't just test fuses visually. Check continuity when the power is off and check AC voltages when power is on. Sometimes the fuse will show contiuity but not voltage due to corrosion or bad connection with the fuse clips.

ken
 
I'll have to take a look. My guess is that there is cold solder somewhere.

I put the switcher back in and played the game a bit.

I'll get back to you.
 
the caps replaced were: c11,c15, c2,c16,c13,c5,c3,c14

VRs replaced: LM723, IC1/IC2
 
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