Denon pma-1080 cutoff after few mins. - diyAudio
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Old 11th August 2009, 09:13 PM   #1
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Join Date: Jan 2005
Location: Bergen
Default Denon pma-1080 cutoff after few mins.

Hi.

I recently bought an well used Denon pma-1080.
But i have some problems. The output is cut off after a few minutes when started from cold.

If I change inputs i can clearly hear that the relays doesn't click as they should. I can also blow into the cabinet left side, behind the transformer and it gets back on.

But if I switch off/on a few times, the amplifier can be ok for the rest of the day.


Do anyone have service manual for this amp. or suggestions in where to start looking for error..


best regards
Andreas
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Old 11th August 2009, 10:23 PM   #2
jaycee is offline jaycee  United Kingdom
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Join Date: Apr 2004
Location: Norwich, UK
check for cracked solder joints
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Old 31st August 2009, 07:46 AM   #3
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Join Date: Jan 2005
Location: Bergen
Default solder joints

Hi.

I've checked for solder cracks, and found a few.. But the problem is still present..

there are some resistors that get hot on the relay-board for the outputs, and those had cracked slodering.

And the board also had evidence from liquid spills..

Do anyone have some schematics for this amp, or a closely related amp? i.e PMA 980R ??
Or where can I get one?

Best regards
Andreas
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Old 3rd September 2009, 08:33 PM   #4
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Join Date: Apr 2009
Maybe the relays are bad.
Measure the power to the relays.
I have 2 denons on is a 980r but i only had a output transistor problem on that one.
Alot of old Marantz from the same time era got relay problems.
I have just bought a defective pma-1560 which turns itself off ,clicks when you try to turn it on.
I will receive this amp early next week and maybe i can give you some idea to your problem.
Optical class A is great.

Pelle
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Old 4th September 2009, 01:10 PM   #5
tricomp is offline tricomp  Denmark
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Join Date: May 2004
Location: Jutland
Hej Andreas,

Send mig en PM med din e-mail adresse.
Jeg kan hjælpe med service-manualen og måske også med et par forslag til, hvad der kan være galt.

Med venlig hilsen

/tricomp
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Old 6th September 2009, 07:01 PM   #6
MatsE is offline MatsE  Aland Islands
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Join Date: Jul 2008
I have a PMA-1080R that I bought used some years ago, and I have had many problems with the relays.

First, the sound in the right channel faded away now and then. I found that the contacts in the output relay were burnt and measured tens of ohms when they were closed. Cleaning the contacts helped for a while, but later I just bypassed the output relays. Which of course disables the protection circuits and muting.

I also had problems with Source Direct. The signal was lost in both channels, if I remember correctly. Never found the cause. I stopped using Source Direct.

Mats.
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