Have to be honest that I dont hang around here much these days, but the G61R died a couple of days before xmas eve, and this thread saved it for me so thanks for that.

Had the G61R (what truly awful design) and the HD621 apart, even more shocking was the use of some really low grade components.
Including not the least the very poorly plated edge contacts for the cards to the backplane - these can be wiped clean fairly easily with IPA and the lightest touch of contact oil should help prevent future contact issues (really do this if you have your G61R apart), especially as the backplane connectors do not provide a reassuringly tight fit suggesting these too are poor quality.

Both units got new PSUs and electrolytic caps, the G61R got a little 40mm fan on the PSU as the local cooling is clearly hopelessly unsatisfactory (already changed the PSU already once before and should have done this last time).

So why bother to bump an old thread? Well as reported above 5.05V (on the processor PCBA regulator per TN20) is clearly significant for reasons I can't be bothered to work out.
5.0V and not working, 5.15V and not working. Not related to the processor PCBA itself I think, but other parts of the product.

hth helps someone in the same situation in future.
happy xmas all.

G61R, 5K5's (fronts & centre), 5K's (sides & rears), D2500, JVC DLA-X70, QNAP, Roon(Pi)