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Colleague's mom used this until it supposedly just died. These things have a standby power supply with some logic and a relay that's switching mains, after the board allows it. Circuit of a very similar one, in fact I haven't found any differences yet. Part no. in the defective unit: BCPS-1120 Part no. in pic below BAPS-1120 https://pic8.co/sh/EgQVqk.png

Edit:Main board https://pic8.co/sh/hdizQD.png

Anyway, relay wasn't clicking. No reaction at all when power was applied and power button was pressed. Search revealed that on these the relay that switches mains goes bad. Put a bridge over the NO relay contacts and the unit came on. Sure enough, the 9 V DC relay coil measured open (MegOhms) when desoldered. Hacked in a new relay that I had on hand and no dice. Bridged the contacts and it went into an on-off loop. Now that I write this, it comes to mind that during testing the Standby PSU was floating, not connected to the chassis. Additional info: Cursory testing of the electrolytics revealed nothing out of the ordinary. What I think is unlikely af, is a relay coil going open and after that is fixed, another fault decides to rear its head. Stranger things have happened but not often.

Any kind of input would be much appreciated. I'll pay in a single upboat.

Edit: Fixed! Turns out it was only the relay that was the original problem. The reason for the other problem was that my colleague hat mangled the little plug that connects the five wires from the standby-PSU to the main board and some of the wires weren't making proper contact any more. I ended up removing the cap from the plug and soldering the wires directly to the little contact springs inside. https://pic8.co/sh/pAESCQ.jpg Seems rock solid now.

Old and new relay https://pic8.co/sh/Kuh1lF.jpg

MPOWERD! (active low) state change standby to powered. https://pic8.co/sh/QqXb8Q.png

Colleague's mom used this until it supposedly just died. These things have a standby power supply with some logic and a relay that's switching mains, after the board allows it. Circuit of a very similar one, in fact I haven't found any differences yet. Part no. in the defective unit: BCPS-1120 Part no. in pic below BAPS-1120 https://pic8.co/sh/EgQVqk.png Edit:Main board https://pic8.co/sh/hdizQD.png Anyway, relay wasn't clicking. No reaction at all when power was applied and power button was pressed. Search revealed that on these the relay that switches mains goes bad. Put a bridge over the NO relay contacts and the unit came on. Sure enough, the 9 V DC relay coil measured open (MegOhms) when desoldered. Hacked in a new relay that I had on hand and no dice. Bridged the contacts and it went into an on-off loop. Now that I write this, it comes to mind that during testing the Standby PSU was floating, not connected to the chassis. Additional info: Cursory testing of the electrolytics revealed nothing out of the ordinary. What I think is unlikely af, is a relay coil going open and after that is fixed, another fault decides to rear its head. Stranger things have happened but not often. Any kind of input would be much appreciated. I'll pay in a single upboat. Edit: Fixed! Turns out it was only the relay that was the original problem. The reason for the other problem was that my colleague hat mangled the little plug that connects the five wires from the standby-PSU to the main board and some of the wires weren't making proper contact any more. I ended up removing the cap from the plug and soldering the wires directly to the little contact springs inside. https://pic8.co/sh/pAESCQ.jpg Seems rock solid now. Old and new relay https://pic8.co/sh/Kuh1lF.jpg MPOWERD! (active low) state change standby to powered. https://pic8.co/sh/QqXb8Q.png
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[–] • 1 pt

Wow, you put a lot of work into helping me. Thank you so much! I edited the OP to include the main board, mainly for posterity, in case someone else needs it.

I'll tinker some more tomorrow or next week if I remember to bring my portable scope. (I didn't this morning) When I hooked the standby power supply up this morning and this time connected it to ground, it worked briefly but quit again, just as I tried to show the guy that owns the receiver.

I'll keep you in the loop.

[–] • 1 pt

It's not that much work, once you start to get the feel for a schematic. I really don't know how to make power supplies, but I've seen enough arcade and radio repairs to know how to start tracking down power rails, which is 99% of "it's broke" problems.