Williams power supply. Not enough 5+ voltage to the CPU/ram board.

[Junt]

[Robotron] Originally the PS was dead. I used the Bob Roberts rebuild kit and brought it back to life, kind of...

I'm getting ~4.7 volts or less to the cpu board at times. It fluctuates so I can get 4.9 sometimes and the games works, but that's not good enough.  I replaced the harness, reflowed solder and reseated connections, etc. I replaced the ICs and caps but not the bridge rectifier as it wasn't in the kit.

Is it worth trying to fix? Are Williams power supplies too finicky? The problem is I can't adjust the voltages, The original Williams doesn't have a voltage adjustment pot. I heard there's a guy that installs them.

Or should I just get a switching conversion kit? The arcade is 100% original with the exception of a repro CPO so I would like to keep the linear in there, what do you guys think?

[Junt]

Pictures:

Bridge Rectifier looks a bit haggard


Previous owner removed the damn header coming from the AC & transformer for some reason but I'm fairly sure its not the problem. I reflowed the solder anyway.

[DarkStar]

When I hear about a power supply starting to fluctuate in voltage, the first thing I tend to think of is a capacitor problem. Do you have an ESR meter to check the input caps?

[iankellogg]

4.7V is enough for the ram but if its fluctuating quickly you have a problem.

[Junt]

I don't have an ESR Meter, I noticed my header pins are a bit rusty and I'm wondering if that's producing some resistance so maybe I'll take a flex stone file to those pins and maybe clean up the rust a bit.

[iankellogg]

that sounds like a good idea, rusty pins can greatly increase the resistance and drop the voltage.

[VertexGuy]

yeah you don't wanna start popping rams.

I shotgunned my Williams power supply , but I wouldn't hesitate to use a switcher if it meant saving my boardset.