Power Issues

[121940kz]

I am working on an S2000 Triple Diamond Deluxe machine. I purchased it, no idea of the history. Overall it's a decently clean machine. It has a 50X board just for added context, the board is professionally repaired. The issue is some sort of power problem, if I pull the main power plug from the backplane and test voltages, they are all over the place, for all the voltages. +25, +13, and the 6~8v they are all over the place. Some start at 12v and then work themselves down. Some start and 5v and move around from 1 to 5v. There is absolutely no rhyme or reason as to what voltage i might get, and it's constantly moving in big swings. Usually starts at some higher value and as i'm watching it, it just slowly keeps creeping down.

For the sake of my testing, the MPU and backplane are not plugged in so they don't come into the equation here, since I have the main power molex unplugged and am probing it from that point.

Service outlet has a good constant 124v, so service outlet is fine.
Tested with 2 other known good power supplies, still the same result.
Unplugged all 3 ballasts
The top fan does comes on when I turn the power on

Doesn't make any sense, I've reseated the power supply many many times.

I guess I'm leaning towards the power distribution board in the inside, I opened it up though, and nothing seems visually wrong. Checked the top fuse on the distribution board and probed it for continuity and it was fine.

Anyone seen this behavior before? What should I try next?

[Stayouttadabunker]

I set my multimeter to 200VDC.
I power ON the machine, stick the red probe into that single black pin on the right of the power Molex plugged into the backplane.
I usually get something like 6.3VDC and it trickles down to 6.2, and 6.1 then bounces back up to 6.3, 6.2, 6.1, 6.3 over and over.
The black probe is just touching the metal floor of the cabinet.

Then I stick the red probe into the back of the Molex where the red wire is coming out of it, and I got a reading of 12.7VDC constant.
Zero fluctuation...black probe of multimeter on the floor.

Finally I stick the red probe into the orange pin right under that red one and I got 24VDC...again zero fluctuation and also with the black probe of my digital multimeter on the cabinet floor.

That 1st pn you check (The single black wire on top of the Molex), should fuctuate a little...the DC voltage falls slightly, like 2 to 3/10ths of a volt...then bounces back up.
I believe it's the capacitor draining then filling back up....normal behaviour.

[121940kz]

I set my multimeter to 200VDC.
I power ON the machine, stick the red probe into that single black pin on the right of the power Molex plugged into the backplane.
I usually get something like 6.3VDC and it trickles down to 6.2, and 6.1 then bounces back up to 6.3, 6.2, 6.1, 6.3 over and over.
The black probe is just touching the metal floor of the cabinet.

Then I stick the red probe into the back of the Molex where the red wire is coming out of it, and I got a reading of 12.7VDC constant.
Zero fluctuation...black probe of multimeter on the floor.

Finally I stick the red probe into the orange pin right under that red one and I got 24VDC...again zero fluctuation and also with the black probe of my digital multimeter on the cabinet floor.

That 1st pn you check (The single black wire on top of the Molex), should fuctuate a little...the DC voltage falls slightly, like 2 to 3/10ths of a volt...then bounces back up.
I believe it's the capacitor draining then filling back up....normal behaviour.

I know, this is not what it's doing though. I'll take a video tomorrow and post it here, I've got other working machines to compare to. I've never seen all 3 voltage outputs do what it's doing, and across different power supplies