DC Offset Issues - Harmon Kardon HK580i

[ChrisP2]

Struggled for several weeks off and on with an HK580i that had 6.7-7.0 VDC at the speaker terminals on one channel and neither the Offset or the Bias POTS had much effect.

Issue was the OEM glue on the back of the Amp board holding down C431 (electrolytic). Over the years the glue had complete dissolved a trace between R433 and the Emitter of Q411. Quick trace repair remedied the issue w/o further problems.

Seen several posts on HK gear of this vintage with this issue w/o too many documented fixes. One more thing on the list to check....

 

[ChrisP2]

Other channel - two bad 100 ohm resistors mid stage to the supply rail.

 

[6taafondo]

Good to know. Thanks for sharing.

 

[audiojones]

Good to know, thanks! I've got one of these that's been waiting for some bench time for a few years now (keeps getting bumped back for more urgent repair work). H/K gear from that era seems to suffer from weak components and solder trace problems fairly often. I had the matching cassette deck in here with similar problems, and the original owner of this receiver said it went in for service a couple of times before with board related issues.