Denon PMA900V idle current adj

KCC · 29th June 2011, 03:49 AM

Last week after some cleaning done on this old amp I decided to do the bias adj following what has stated in the service manual. I bought this used and the left channel sounded a bit unclean. It is otherwise ok.It turned out I managed to fry all output ransistors and then some. So,tonight,I have all of them replaced and started measuring.I connected to the test point next to VR5 and noticed the voltage reading is much higher than what suppose to be. 0.4v to 0.4mv. And VR5 is at min(highest resistance). I am thinking some resistors might be bad. I would appreciate advices on this matter and thanks in advance.

KCC · 4th July 2011, 02:47 AM

Ok. So after some testing on resistors and transistors I've found some of them are bad.Ao that's a good start.Although I wondered what cleaning steps will cause the output transistors and related components to burn.

29th June 2011, 03:49 AM	#1
KCC diyAudio Member Join Date: Mar 2002 Location: Edmonton	Denon PMA900V idle current adj Last week after some cleaning done on this old amp I decided to do the bias adj following what has stated in the service manual. I bought this used and the left channel sounded a bit unclean. It is otherwise ok.It turned out I managed to fry all output ransistors and then some. So,tonight,I have all of them replaced and started measuring.I connected to the test point next to VR5 and noticed the voltage reading is much higher than what suppose to be. 0.4v to 0.4mv. And VR5 is at min(highest resistance). I am thinking some resistors might be bad. I would appreciate advices on this matter and thanks in advance.

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4th July 2011, 02:47 AM	#2
KCC diyAudio Member Join Date: Mar 2002 Location: Edmonton	Ok. So after some testing on resistors and transistors I've found some of them are bad.Ao that's a good start.Although I wondered what cleaning steps will cause the output transistors and related components to burn.

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