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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Bob Urz wrote in message
...
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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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
http://home.graffiti.net/diverse:graffiti.net/

"Bob Urz" wrote in message
...
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.


**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



--
Posted via a free Usenet account from http://www.teranews.com

"Trevor Wilson" wrote in message
.. .

"Bob Urz" wrote in message
...
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.


**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.



Ditto

Arfa

Bob Urz wrote:
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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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 .

Mark D. Zacharias wrote:
Bob Urz wrote:

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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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 .


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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Bob Urz wrote:
Mark D. Zacharias wrote:
Bob Urz wrote:

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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Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service
in the World! 120,000+ Newsgroups ----= East and West-Coast Server
Farms - Total Privacy via Encryption =----


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 .


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


Cool!

mz