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Denon AV reciever shut down

I got an Denon AV receiver in that immediately goes into shutdown. Plug it in, no display. Hit the momentary power up switch, relay clicks by small power transformer, display goes through two different displays, relay clicks again and display goes mute. It says nothing on the display about protection or such. Non of the outputs seem to be shorted. Ot seems like a classic case of outputs shorted and the unit shutting down, but the outputs are not shorted and the display does not say protect before it goes blank. I resoldered up the main board and no change. ESR'ed the caps and nothing jumped out bad. DOn't have the print yet but that next if the customer wants to pony up more bucks. Any ideas on the shutdown? I'll post the model number latter.

Bob

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Reply to
Bob Urz
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Perhaps something like a zener has drifted so its falsely registering an imbalance of B+/B- or something. If you are loathe to temporarily disable the protection cct,for diagnosis, try adding a power diode or into one DC rail and then the other to see if there is a change.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N Cook

**In cases like this (all too frequent, with modern equipment) I bypass the power relay contacts and ramp the unit up with a VariacT. Watch for smoke, of course. 
--
Trevor Wilson
www.rageaudio.com.au
Reply to
Trevor Wilson

Ditto

Arfa

Reply to
Arfa Daily

Had a Denon recently with a similar problem - it was a bad 7815 regulator. It was necessary to disable the protection circuit by lifting a diode in order to troubleshoot. In my case bypassing the relay didn't work - it still triggered the protect without revealing any cause, since the problem disappeared as soon as the protect triggered. When the protect was disabled a wall-to-wall 60 hz sine wave appeared at the output of the amp. Good thing there was no load at the time...

MarkZ .

Reply to
Mark D. Zacharias

Thanks Mark, you got me on the right track. I had the high voltage rails. But the center voltage on all the outputs was 1/2 of the B+ rail. I had hot wired the turn on relay. There was a 5 volt 3 legged regulator and it was fine. BUT, right next to it was another low rail with 4 discrete diodes with a 1/2 watt resistor in series with the power transformer. This resistor was open. None of the diodes were shorted. replaced the resistor, checked all else, and it fired up.

Bob

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Reply to
Bob Urz

Cool!

mz

Reply to
Mark D. Zacharias

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