marcoeloco
New Member
Hi all, I agreed to have a look at a friend’s Kenwood ka-5500 amp, and now I’m thinking maybe I shouldn't have. He told me it had a fault with the speaker protection on one channel and when the amp is turned on one of the meters went to full scale and the protection relay cut out.
I decide to have a look and recap it fully as it had been sitting for years. I thought I would recap it first and then try and find the problem as it may have been a cap causing the problem. It wasn't.
After firing up the amp the same problem occurred in one channel and then it changed. Sometimes the meter will float up a small way and others it will go up more quickly and cut out the relay.
I check all the voltages from the power supply, control amp, and power amp.
I checked the bias, dc offset and it was all ok
I found up to 5 volts ac and the speaker output depending where the meter was and also the base of the main output transistors. I traced the voltage back a bit further but it was too hard with the board in the amp. I decided to remove the board and remove all the transistors on that channel check them I did not find a problem. I then re soldered all points on the board. I am hesitant to put the board back as I don’t think I have found the problem.
Any ideas as to what could be causing this?
I decide to have a look and recap it fully as it had been sitting for years. I thought I would recap it first and then try and find the problem as it may have been a cap causing the problem. It wasn't.
After firing up the amp the same problem occurred in one channel and then it changed. Sometimes the meter will float up a small way and others it will go up more quickly and cut out the relay.
I check all the voltages from the power supply, control amp, and power amp.
I checked the bias, dc offset and it was all ok
I found up to 5 volts ac and the speaker output depending where the meter was and also the base of the main output transistors. I traced the voltage back a bit further but it was too hard with the board in the amp. I decided to remove the board and remove all the transistors on that channel check them I did not find a problem. I then re soldered all points on the board. I am hesitant to put the board back as I don’t think I have found the problem.
Any ideas as to what could be causing this?