2230B got 27V DC in power amp input!

[Romer]

Hi,

Got a non working 2230B from eBay and planned to repair it myself.
Tuner and pre amp sections work well but power amp has 23-27 V DC in one of the channels input, that is J701 in diagram. Voltage rises from 23 to 27 as power transistors and heat sink warm up. And they get hot in short time. I also disconnected incoming wires from pre-amp to make sure it's not pre-amp's fault, and still high voltage in input. This time I didn't have much time to dig into deeper. So, how such voltage can get to input?
Asking you guys first, what you recon where the problem lies, before I open it up again?

Diagram PDF file: https://goo.gl/GZCCkV
Thank you.

 

[culcuhain]

Service manual and start tracing the power from start to finish ( or the halfways style: check halfway, if good then go halfway between there and end. If bad go halfway between there and the start. Repeat) . Remember that DC is like water and it flows to ground.....

 

[mech986]

Yep, divide and conquer!

If there is actually DC on the input, sounds like the Differential pair is shorted or C701 (3.3uf/25V electrolytic, blocking cap) is shorted.

For those who don't have a dropbox acct:
http://akdatabase.org/AKview/albums/userpics/10004/Marantz 2230B Service Manual.pdf