Help with bias adjustment.

victo · 9th December 2012, 09:59 PM

I recently bought a JVC A-X9 amp. There is no problem with the sound and no difference between the channels. But one of the channel's heat sink gets much hotter than the other. I checked the DC offset and bias voltages as described in the service manual. I am able to adjust the dc offset for both channels. When it comes to bias, I can adjust the bias of the channel which is getting hotter, but the cooler channel's bias pot is not adjusting, the mV reading from the test point is always constant.

All the capacitors are original and I cant see any leaking ones.

What to look for? What can be the problem?

whizgeek · 9th December 2012, 10:12 PM

Start with mechanics, first the pot. then wiring to the bias transistor (not sure if there is one separate)
then measure and compare volts at the bias pots.

9th December 2012, 09:59 PM	#1
victo diyAudio Member Join Date: Dec 2012	Help with bias adjustment. I recently bought a JVC A-X9 amp. There is no problem with the sound and no difference between the channels. But one of the channel's heat sink gets much hotter than the other. I checked the DC offset and bias voltages as described in the service manual. I am able to adjust the dc offset for both channels. When it comes to bias, I can adjust the bias of the channel which is getting hotter, but the cooler channel's bias pot is not adjusting, the mV reading from the test point is always constant. All the capacitors are original and I cant see any leaking ones. What to look for? What can be the problem?

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9th December 2012, 10:12 PM	#2
whizgeek diyAudio Member Join Date: Feb 2010	Start with mechanics, first the pot. then wiring to the bias transistor (not sure if there is one separate) then measure and compare volts at the bias pots.