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Vintage HK protect mode?

Is there one common cause for the longer delay time in protect mode typical of vintage Harman Kardon amplifiers? Or is the cause any one of 100 possiblilities?
arnettpartners
magfan
1,583 posts
 
In general, I'd say NO. Not too hot, since when turned on, it's stone cold.

Too high a bias? Don't know if that could trip some protection circuit. Maybe if the circuit 'interprets' that as a short? That'd do it.

In any event, a trip to a tech is indicated. Choices are stuff like bias adjust, or time delay relay problem. Weak output device, going bad? Don't know.
Such relays are fairly reliable, but also a moving part....That click you ordinarily hear is the relay 'flipping'. which means it can wear out.
arnettpartners OP
312 posts
 
OK. Thanks. I have a tech lined up who loves to work on vintage.I never thought of that--the click. Like a solenoid. The click can wear out. Cool. Thanks.
arnettpartners OP
312 posts
 
Getting back to you guys on the Citation 24 protect mode after getting it back from the tech today. Tech's note: Located and replaced 2 faulty capacitors in protection logic circuit.

I think I found a good tech. He says, disassembled and cleaned pc boards and chassis. Pulled speaker output jack. Plastic broken and cracked. Fabricated support for speaker output jack and jack panel. Checked components for correctness as much as possible. Bias is dead on. Resoldered a few suspect connections on output board. Inspected driver/regulator board-ok. Reassembled and bench tested. Works great. Flat rate $90

For anyone who might be interested, from the research and anecdotal info I found, I believe that the quality control issue regarding the factory bias settings is misinformation. A source who is an agon member told me that the left channel bias circuit board contained an error on both the 22 and 24 which does not agree with the schematic and which he found and corrected on his own amps.
I have run into owners on the net whose amps ran hot and the left channel subsequently burned up. I believe that at some point in production Harman found the error, if not before, then after the amps started burning up, and corrected it during production. Otherwise, I don't think there would be any 22's or 24's left.

Regards,

Lynne
hifihvn
943 posts
 
Sounds good. I hope you enjoy it.
arnettpartners OP
312 posts
 
Thanks. I might have added that I'm a little surprised by the sound quality. I like the new stuff and I bought it as a gift for someone who likes vintage. It's soft and full and quick. I can understand why the owners have no desire to upgrade. I wouldn't either.
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