Harman Kardon HK6000 DC out problem


2014-08-28 11:03 am

I am looking for an advice regarding Harman Kardon HK6800 integrated amplifier repair.
I have quite unusual situation where DC is present at the both outputs (okey, 2 burned speakers as I haven't checked before connecting). The mystic is that power section is good and I done all alignments of voltages/currents there. DC starts from pre-amp part to the Volume potentiometer and futher. DC level is about 10V on both channels and varies along with potentiometer. If connected to main amp, the output level goes up to the supply rail.
DC is found on the connector CN507 on the other hand connector CN502 is DC-less and carries good AC signal form inputs. Related part is presented below.
Imgur: The magic of the Internet
Full SM can be found at:
Harman Kardon HK6800 - Manual - Stereo Integrated Amplifier - HiFi Engine
Have checked that board, nothing bad at the first glance. Will investigate transistors next day once again. By the way, Protection lights up only at the startup and goes off like normaly. Nothing burned or loose too. Voltages are present, control switches and LEDs working as usual.

Maybe anyone had similar situation and could help to speed up this repair as the assembly of the amplifier is quite robust and repair-proof.