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First thing to do is get a little spray can of DeOxit. Turn the radio on it’s back with the front panel up. Hold a rag near the attenuator switch assembly to stop any over spray on?the outside of the panel.?
Flip the switch up all the way to max attenuation and gently push the spray nozzle tube into the little space under the toggle and give it a little shot of the DeOxit. There is a small rectangular felt gasket under the panel the toggle bat passes through and you can get a little shot of DeOxit solvent past it into the switch mechanism. ?
Then flip the ATT switch up and down a half dozen times or so.?
Now do the same thing with the spray nozzle tube but with the toggle switch all the way down.. repeat the single spray shot and flip the switch up and down a half dozen times. ??
If the contacts are dirty in that switch it wipes out all the radio’s receive signal.?
If this does nothing for you problem then move on to other issues. One of which could still be a bad ATT switch!!