Kenwood KA-6100 BIAS to high - diyAudio
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Old Yesterday, 08:00 PM   #1
idntr is offline idntr  Germany
diyAudio Member
Join Date: Aug 2013
Default Kenwood KA-6100 BIAS to high


I'm currently restoring a Kenwood KA-6100. Most of the caps are replaced and so far it's sound quite nice.

But I'm not able to get the BIAS current to the specified 20mV. Left: ~50mV, right: ~60mV. The BIAS potentiometers are already on the lowest position...

Any suggestions?

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Old Today, 12:19 AM   #2
llwhtt is offline llwhtt  United States
diyAudio Member
Join Date: Jun 2008
Location: SoCal
Both channels? Does the idle current adjust at all? Will it adjust higher? If THm1/2 is open idle current will be high, what are the chances of both channels though? Boot strap capacitors Cm53/54 installed correctly?
Basically your problem is that the voltage on the base of Qm17/18 is too negative. Sometimes the pots are shot, try removing and measuring. The wiper of VRm5/6 should go to zero Ohms at both ends. Full cold would be wiper at the VRm5/6 and Rm87/88 junction, least negative position.


Last edited by llwhtt; Today at 12:29 AM.
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Old Today, 12:14 PM   #3
idntr is offline idntr  Germany
diyAudio Member
Join Date: Aug 2013
Yes both channels, with ~10mV difference. Both are higher adjustable. When the amp is cold it's 35mV left and 40mV right. Cm53/54 are replaced and should be fine.

sorry, but I don't get the last sentences..
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