I see you just got your M-506RS recently; mine should be arriving this Wednesday; how do you like yours so far? I was looking into the servo feature too. You have to have an Onkyo preamp that supports this feature and a special cable to connect from the pre-amp to the power amp. There was a discussion at the link below about the servo feature and after reading it, I don't think it makes much of a difference.
Thanks for the update, I already ordered some red ones I found on Ebay; they will be fine as they are only on for a few seconds, it doesn't matter to me if they are amber or red. I agree with you about the servo being BS otherwise Onkyo would still be using it. I don't have the matching preamp but I'm using a Denon AVP-8000 tuner-preamp which I like a lot and I didn't want to have to replace it just so I could use the servo feature.
My M-506RS is arriving tomorrow and I plan to check the DC offset voltage. Do you happen to remember which pots you used to adjust the DC offset voltage. I downloaded the service manual from hifiengine.com and all of the adjustments are on pages 5-7 but I couldn't find anything on how to adjust the DC offset voltage. It is a crime that you left that in the garage for 12 years but you got a great deal getting that for free.
I couldn't find anything in the M-506RS service manual about how to adjust the DC offset voltage either. You said you tried to adjust but wasn't sure if you did it right. So how did you do it and were you able to lower the DC offset voltage at the speaker terminals. Out of curiosity I also looked at the M-504 service manual and it doesn't have any thing about adjusting the DC offset voltage either.
I picked up the Onkyo P-304 and M-504 today for $750 and I'm really happy they both are in excellent condition and sound really great. The only Problem is the left RCA output jack on the P-304 is missing the outer metal ground around the plastic connector housing. My cable still plugs in securely around the plastic that is left. I haven't noticed and hum or any effect on how it sounds [Mod Edit]
The weird thing about the M-504 is that when I plugged in my banana jack speaker plugs I wasn't getting any sound from my speakers but when I removed the banana plugs and just used the speaker wire and screwed the terminal down tight then the speaker worked fine. It seems the M-504 has really deep plastic receptacles or slightly larger than normal as my 4mm banana plugs were loose fitting and I had to bend them out a little to make them fig snugly so maybe that is the reason they are not making contact. It seems I need to find a banana plug that is slightly larger and maybe longer as well, as mine aren't making contact with metal only plastic. So I'm going to have to find some longer and larger ones that will work on the M-504. This is very odd because of been Pomona 1825-2 and Pomona 1825-0 banana plugs for over 40 years and they have worked on every speaker and amplifier I have ever had except for the Onkyo M-504. I can buy the Pomona banana jacks at my local Fry's Electronics in a 2-pack for $5.19; they are very study so it's a shame they won't work with the Onkyo M-504. Are there 6mm banana plugs? I'm thinking a 6mm plug might work with the M-504.mron The Onkyo M-506RS that I bought on Ebay arrived damaged and I had to return it. I ended up buying a M-504 on Craig's List and I like it; I just wish it had the level controls and meter range switch like the M-506RS has. I also found out the M-504 uses eight four pin 9,000uf capictors in the power supply which aren't sold any more which means you have to use two pin capacitors and modify the circuit board to make them work. Do you know if the four 22,000uf capacitors in the M-506RS are also of the four pin design?
