I removed my original JP power supply board when the HV leg appeared to have failed (for the DMD). I replaced with a Rottendog board as this seemed the shortest path to confirming my issue was with the DMD or the PS itself, and getting the machine back into playing condition. All is well.

As I have some time available now, I thought it might be a fun little project to try and diagnose and repair the old board. No harm, no foul if I fail.

Questions:

1. What's the best method to get power to this board to test my repairs? I'd much prefer not to have to insert/remove from the JP backbox until I am confident the board is functional. Plus, accessibility of the PS behind the backbox door hinge a real pain in the butt.

Is it reasonable/feasible to make an extension cable (~15ft to my bench), and connect the 4 wires coming off the transformer via the nearby Molex connector? These are pretty hefty wires (2x White, 2x Yellow); what AWG and Pin diameter here?

2. Any other connections required to confirm output voltages from the remote PS Board?

Any suggestions or cautions?

Thanks John,

I'll proceed as you suggest.

The PS is not terribly dense so a pretty quick check with a DMM.

1. Found a cracked diode (D5, 1N4004), but the remaining diodes checkout ok. I have a pile of these so will make the quick repair
2. No open or shorted legs on the bridge rectifier
3. No open or shorted resistors
4. No shorted transistor legs
5. No shorted, leaking or swollen caps
6. Did not know where to begin with the relay - nothing burned or visually obvious.

I'll take another pass when I return this evening

For testing zeners, is there much more to check with a DMM in ckt than short or high resistance in both directions?

D5 was it. Zeners all looked and tested as expected. Yeesh, a $0.05 item.

I'm thinking of leaving the original DE PS board in place, and holding on to the Rottendog board just in case...

I also think the JP 60Hz speaker hum is somewhat reduced with this old board than with the Rottendog board. Hmmm.

dup