Hi all, I know this is an old thread, but it helped me repairing my RX V663.
Mine switch on, but of after one second it would switch off again.
Pressing and holding 'straight' and 'audio select' followed by pressing POwer On worked as some kind of override, so it would show me an 'PS2 PRT' error.
Using 'INFO' and 'TONE' combined brought me in an 'Advanced Setup', where test no. 8 would show a PS1 of 145 (OK, it's within the 110-255 limit),
but the PS2 value was L077, so I assume Low with a value of 77.
The limits for this test are 88-140, as shown on page 47 of the service manual.
It turned out to be an all plastic KIA 7812 positive regulator on the MAIN-2 board, I could check the voltages on connector CB303 of that little board, it's accessible from the top of the Amp, it was only 1,56V
This board is a 25 cm long and 3cm wide board, attached to the main cooling body in the center of the Amp.
With some fiddling I replaced IC104 (7812 regulator) with a 1.5Amp version that had a metal cooling tab as well.
I did put insulation between it to be sure, since the original had a plastic housing, so I did not want to create an unwanted ground loop of some sort.
After the replacement the 12V came back as normal.
After that I had to perform a full reset by going to step 23 of the Advanced Setup menu.
Turn the knob to select 23, then press one of the 4 audio field select buttons, it will show Preset RSRV.
Now power off the Amp, all done.
Un saludo,
Leo