Kenwood KA-8011

[rokoc007]

Hello guys,

I would like to ask something about my ka-8011 which is same as kenwood ka-801. I don't have the amplifier for long time and it is working lets say normally.

It was surprise for me when I opened bottom cover and saw this.. Path to Q1 collector burnt. What can cause this and how it is possible that it can still working with burnt path ?

Thanks a lot

 

[latala]

I would strongly suspect that you have a faulty Q1 and the amplifier has opened circuited the track th e amp is using Q5 only I would first check Q1 for shorts between collector and emitter if this measures ok I would then link the bad track out if faulty replace both Q1 and Q5 with a matched pair

 

[rokoc007]

thanks for advice latala, I checked Q1, looks good, there is no short between collector and emitter. Maybe I should fix the line and hope that there will be not a firework 😀 But I am not sure how this can happened..

 

[latala]

if the amplifier was mine i would be tempted to repair the burnt link and try the amplifier again

 

[rokoc007]

hi, so I fixed burnt link, also had to change bias trim pots and some zener diodes, some capacitors 😀 I had trouble with high bias, but now is stable and I'm able to set it to 18mv.

 

[latala]

Is the 18 mv the total bias or is it per transistor
Well done the repair looks to be ok

 

[rokoc007]

I think that it is total bias, I set it according to service manual.. also found two black flag caps