So I've isolated my problem, to having the 5v rail, go from 4.98 fairly steady, to 1v once plugged into the mainboard, nothing else is connected as I wanted to isolate the issue.

To step back, I re-did the caps (all of them) on the SDB about a week ago, and it's been playing fine for about a week (20 Games). Then Friday evening I put some Cliffy protectors in, all the hardware that came out, went back in, no surplus nothing missing. So I'm fairly certain it's not something that's shorting anything out on the board. Saturday Morning I come into the room, turn it on, and the GI lights are on, the DMD is dark, and I look behind the black glass, no diagnostic lights +5v etc..

So I turn everything off, and start reading and diagnosing, because I don't have any diagnostic lights on the CPU, I can't / won't get anything on the DMD, because it also has nothing to go off of, because it hasn't been sent anything. I remove all connectors to the CPU Board, and just connect the wires next to the battery tray, (Game is NVram so no battery leakage that anybody can see / detect). And power it on, nothing on the diagnostic led's.

I take the game out to hook up to one of my PC Power supplies 5v supply, and lo and behold it powers up, goes through diagnostic, and gives me two red lights. (normal)

So since the CPU is good, and tests well with 5v, didn't blow a breaker or anything for drawing too much, I focus back on the power supply, the odd thing is I haven't touched that thing in a week. Before then yes it had several old caps, so that's why I replaced them, I had a low 12v side @ around 10.1v, I matched polarity, and microfarads. Everything I was supposed to... and it ran...for a week, but maybe the new caps put stress on some of the other old components?

I just re-flowed the bridge rectifier, and still same sad story.

Any thoughts?

Thanks!

I have tested C2 five days from sunday, I have an ESR tester and I tested C2 in and out of the cuircuit, and both read low ESR, and said the cap was good at 25v.

I can't find BR1 But I have checked and wiggled all the fuse holders, and there seems to be no "lose connection"

TR5 has been in my cross-hairs, I would most likely have to remove it to verify it works, and I have a transistor tester but I'm used to testing itty bitty little ones, that fit into the slot on the meter, this monster I'd have to extend the leads with alligator clips, I am worried that when I tested any signal on any of the 3 wires that lead up to the transistor I couldn't find any voltage on any of the 3 legs.

I have also measured continuity to all caps from the component they're connected to, through the pcb, to the part of the pin that pokes above the solder, I also have re-flowed the connector and measured continuity from the header pin to the first component it connects to through the pcb, all is solid.

I made sure I had it done properly, I took pictures before, and I took a picture just now...

The Bridge I re-flow-ed, but like I said it worked before, so if Polarity was wrong, I'd hope it wouldn't work before.

So it worked when I originally got the game (of course) about a month ago, I had some issues with 5v being around 4.1v so pretty bad but still functional, I got a cap tester, and tested the caps in the board, and a couple measured out of spec or the caps were 1000 microfarad, and the meter read, it's fine as long as the cap is less than 470 microfarad (Not exactly what it said, but it was less than what it was supposed to be rated at) so I replaced those, then I got a Pinsound Card, and it wasn't happy it said my 12v rail wasn't getting enough power. When I pressed on the caps, it stopped complaining for a little while and then it was back. So I swapped the rest, I got my cap kit from Yorktown Arcade Supply. So they were all brand new, and I matched polarity, and uF for each one I replaced. And Tested continuity from the soldered pin, to the next component by tracing the trace on the board, or looking for it in the schematic.

It then ran for another week flawlessly with pinsound, while I was waiting for a Cliffy Kit, to reduce some of the holes from wearing. I replaced all the holes, and marveled at how much more straight and predictable the machine became, and me and my son played 3-5 games, stepped away, and played another game before bed 10pm. I left the machine running and then finally turned it off before going to bed myself 12pm-1am and woke up the next morning 7-8 turned it on, and GI was on but no life from the DMD, so I knew something was bad...

I've had my head buried in forums, and trying to figure out what could be bad. I've been learning a lot, so I'm not mad, but I also want to resolve this.

PoweBoardRebuild (resized).png

Pin 4 and 5 read 4.97v under no load,
1.06v, and 1.86v under load from the cpu

So I ordered another transistor (TR5) for the heat sync, and another chip with a socket(LM723 ), we'll see how it goes. I'll try and update the thread as I go.

Well that didn't work....
I replaced the TR5, made sure that it plugged in the same way, since the plugs are on one side of the circle.
LM723, I added a socket for the chip making sure it matched the silk-screening and testing continuity, form the pin to the next component, and then inserting the chip with the same notch away from the big caps, and I get different voltages 1.02 and 2.07 on pin 4 and 5 under load, which would indicate that the failure was someplace else... I'm just not sure what I'm looking for, I can try all the diodes, but I feel like I'm just fighting windmills.

So I now suspect the relay, as F1 and F2 have no voltage, and yet have good continuity from the fuse holder to the fuse holder and the fuse itself.

I think the relay is a symptom not a cause, since it doesn't have the proper voltage to energize it or trigger it from the mainboard.