- Joined Jul 21, 2015
I'm trying to fix a hum that appeared on one channel of my Radio Shack/RCA SA-155 integrated stereo amplifier. Does anyone have a schematic for this amp?
Thanks. This is exactly what I needed. Also your advice. Will follow this up.Check the coupling capacitors that should be connected to pins 2 and 6 of the main amp IC (LA4440). I would also check the main power supply capacitors. These may be allowing 60 cycle hum although I would expect both channels to be affectedinthis case.
Thanks Joe. This schematic will help a lot. I just checked the headphones. Good suggestion. The hum is absent! The signal at the speaker is a 120 Hz sawtooth, 0.4 V pk-pk but sounds like 60 Hz hum and is unaffected by the volume control. Pic of waveform attached.You can get the SA-150 schematic and compare the two. You might get lucky.
on edit ... Did you listen using your headphones to see if the hum was still there?
Attached is similar to the SA-150 schematic.
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