Receiver has dead channel

[spark1]

Great tip. Thanks.

How did you clean the selector and monitor switches?

 

[spark1]

Thanks. I pulled the board that I believe is the left channel pre-amp. In the photo it's the left VERTICALLY mounted board with the two gray capacitors (not sure how to confirm this). I will test the components on this board.

The preamp section will be on one board (both channels). Also, while not relevant to the problem at hand, this receiver has capacitor coupled outputs. So, there is not a DC offset to measure.

 

[petes'picks]

You can measure DC offset with a 8 ohm resistor across each channels speaker outputs. It may not be deadnuts accurate but it works for me.

 

[spark1]

Yes, you can measure DC leakage with a load. Some cap coupled amps allow for center voltage adjustment, but there is no afjustment for for DC offset. Effectively, you are measuring leakage from the coupling caps. If significant, the caps should be replaced.

 

[BigShooter]

Check the ground(s) of the selector switch.

You said input from tape monitor works fine. This means the preamp and power amp sections are good.

The tape monitor switch is after the selector switch and before the preamp/tone/volume. Seems like the problem must be before the tape monitor switch (or, as I said earlier, is due to the tape monitor switch failing to open completely when off). If before the tape monitor, that would suggest the selector.

Problem is all sources, so it is not at the inputs. That leaves the selector, I think.

Great advice. Thanks for the help, I will look at the selector ground(s). I will clean both the selector and tape monitor switches one more time for good measure.

 

[spark1]

Great advice. Thanks for the help, I will look at the selector ground(s). I will clean both the selector and tape monitor switches one more time for good measure.

To be clear, in the absence of a schematic, I am doing some "educated" guessing, based on how tape monitor switch works on other units with which I am familiar.

As regards cleaning...I would focus on the tape monitor switch. You are getting exactly the same result with all inputs; if the selector contacts were the problem, I would expect there to be some variance between inputs. But also still check wiring and joints/connections from selector switch onward to preamp. It may be that the monitor switch has its own path to the preamp, altho I would guess that it is same path as from the selector.

Can you post a pic of the tape monitor switch, and describe how you cleaned it?

 

[spark1]

Bueller? Bueller?