I have a T7820 and it worked amazingly well until about a week ago. Nothing happened that I'm aware of (no power surges/I didn't drop it/etc...) but when I went to turn it on, it didn't seem to work.

I see the LED on the power button flash yellow 4 times, then white 4 times, then a long pause, then the sequence repeats.

The manual says that the 4-4 blink code means:

Riser board issue
Power issue on Riser second CPU board

I'd really, really, really like to get this working again but I don't have a ton of experience with hardware issues like this.

1. If I remove the 'riser' unit completely, the machine boots up and seems to work fine.
2. I've used swapped both the 10-pin power cable and which 'port' the cable is plugged into to receive power from the power supply. IE both cables and both ports are able to power the first CPU as long as the riser is not attached

What should my next step be? Is it possible that my power supply is defective and I should order a replacement, because it's not able to give enough power when the riser is attached anymore? Or would that be a different set of flashing lights.

Is there something else I can do to the riser unit to fix this power issue? Or do I just need to order a new riser, then install my ram/cpu into it?

Any help would be greatly appreciated.