Neroskillo
New Member
Hello dear Forum members,
I am new to this site and also rather new to repairing audio stuff. I've done amplifier 2 re-capping projects succesfully and am trying to save this KA7002. It is a bit of a Family piece, because it belonged to my father in law, and my oldest son wants to use it now in remembrance of him.
So I already fixed 1 channel that was bust, because of a bad tor in one of the tone pre amp stages.
Then I decided to do some extra tor replacements. Also exchanged the main amp C's. And last I decided to replace the power supply cap's.
All went according plan, but.... seems there is something wrong in the power amp stage.
R42 is getting hot (see attached schematic) as are Q5,6,7,8. Hot meaning 65°C. The end stage tor's are ok though. Not hot at all. I didn't as yet check the quiescent or bias current. But before doing that I want the hot spots out. Or is this related to the VR1&2 not being adjusted as they should.
Sound is quite ok, except that the unit seems very sensitive now for cell phone signals. But that's maybe due to fact that it is all out open now.
There's another thing that is strange. The signal input of the power amp is drawn as R then C on schematics. But on the PCB phantom view it is the other way round: C then R. Does this matter in any way? And what is the correct way? I gather that the C serves as high pass filter and/or DC cut-off from previous stages.
I am new to this site and also rather new to repairing audio stuff. I've done amplifier 2 re-capping projects succesfully and am trying to save this KA7002. It is a bit of a Family piece, because it belonged to my father in law, and my oldest son wants to use it now in remembrance of him.
So I already fixed 1 channel that was bust, because of a bad tor in one of the tone pre amp stages.
Then I decided to do some extra tor replacements. Also exchanged the main amp C's. And last I decided to replace the power supply cap's.
All went according plan, but.... seems there is something wrong in the power amp stage.
R42 is getting hot (see attached schematic) as are Q5,6,7,8. Hot meaning 65°C. The end stage tor's are ok though. Not hot at all. I didn't as yet check the quiescent or bias current. But before doing that I want the hot spots out. Or is this related to the VR1&2 not being adjusted as they should.
Sound is quite ok, except that the unit seems very sensitive now for cell phone signals. But that's maybe due to fact that it is all out open now.
There's another thing that is strange. The signal input of the power amp is drawn as R then C on schematics. But on the PCB phantom view it is the other way round: C then R. Does this matter in any way? And what is the correct way? I gather that the C serves as high pass filter and/or DC cut-off from previous stages.
![IMG_4053[1].JPG](/forums/data/attachments/1719/1719376-7d07761fd0ddfde94d5d19bec7b052f3.jpg?hash=fQd2H9Dd_e)