WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
My friend asked me to fix this preamp, it has a background hum like 50 hertz and one channel receives radio. I opened it and saw that one resistor in the power supply was burning.
Guys anyone having the kta ls-1 diagram? and any experience with these?
I would recommend that the HV electrolytics be replaced I suspect 1 or both of them are bad at this point. The burned resistor is in the HV supply and there are no current levels in normal operation that would cause the damage I see.
Would also explain why it is noisy. These were very quiet units. I used one in a secondary music system for a number of years before selling it to a friend here in MA who still has it last time I checked.
This particular unit is 20 years old. There was a matching phono stage.