Hi All,
I'm trying to fix this 40+ year old power amplifier which works but has a couple of issues:
When powered up without an input signal and the volume pots set to zero there is a noticeable high frequency interference coming through the speaker outputs. If I switch off the amplifier the interference disappears. The massive smoothing caps (14,000uF/100V) continue to power the amp for some time after the power is cut. I've attached the service manual, some oscilloscope screen dumps of the speaker outputs with the power on & off.
Any pointers would be most welcome.
Thanks.
I'm trying to fix this 40+ year old power amplifier which works but has a couple of issues:
When powered up without an input signal and the volume pots set to zero there is a noticeable high frequency interference coming through the speaker outputs. If I switch off the amplifier the interference disappears. The massive smoothing caps (14,000uF/100V) continue to power the amp for some time after the power is cut. I've attached the service manual, some oscilloscope screen dumps of the speaker outputs with the power on & off.
Any pointers would be most welcome.
Thanks.
Comment