Hi,
I just bought a Kenwood KR-5030 from a guy for cheap because it "didn't work". ( I'm new to amplifier repair/restoration, but I've been an electronic hobbyist on and off over the years.) So far I've fixed the power switch - a well known issue with this amp, cleaned the controls, and cleaned up the relay in the protection circuit which was too crudded up to function. I replaced the caps in the power supply, including the large filter caps. It's working pretty well and sounding good so far.
My question: I've got non-zero DC offset - 15 mV in one channel, 35 mV in the other. I bought a bag of 2SA750's from the auction site, that's the transistor in the input differential pairs, and I'd like to find two tightly matched pairs and put them in. Do I try to match VBE or hFE, or both?
I have tried to read up on this question before posting, but opinions seem to vary a lot and the answers seem to depend on the situation.
Thanks,
Rob
I just bought a Kenwood KR-5030 from a guy for cheap because it "didn't work". ( I'm new to amplifier repair/restoration, but I've been an electronic hobbyist on and off over the years.) So far I've fixed the power switch - a well known issue with this amp, cleaned the controls, and cleaned up the relay in the protection circuit which was too crudded up to function. I replaced the caps in the power supply, including the large filter caps. It's working pretty well and sounding good so far.
My question: I've got non-zero DC offset - 15 mV in one channel, 35 mV in the other. I bought a bag of 2SA750's from the auction site, that's the transistor in the input differential pairs, and I'd like to find two tightly matched pairs and put them in. Do I try to match VBE or hFE, or both?
I have tried to read up on this question before posting, but opinions seem to vary a lot and the answers seem to depend on the situation.
Thanks,
Rob