I have a National RAO-7 military receiver that I recapped about 5 years ago.
I also replaced a few out-of-tolerance resistors. The receiver performed
well beyond original specifications at that time. It was unused for about
the last 2 years and now when I listen to it, I get distortion in the audio
output at about 1/3 to 1/2 volume. The more I increase the volume, the
worse the distortion becomes.

What might this be a symptom of?

Thanks in advance for your advise and help.

Cal in TX

Leaking interstage coupling cap? Were these replaced?

Beech Creek wrote:

I have a National RAO-7 military receiver that I recapped about 5 years ago.
I also replaced a few out-of-tolerance resistors. The receiver performed
well beyond original specifications at that time. It was unused for about
the last 2 years and now when I listen to it, I get distortion in the audio
output at about 1/3 to 1/2 volume. The more I increase the volume, the
worse the distortion becomes.

What might this be a symptom of?

Thanks in advance for your advise and help.

Cal in TX

Beech Creek wrote:
I have a National RAO-7 military receiver that I recapped about 5 years ago.
I also replaced a few out-of-tolerance resistors. The receiver performed
well beyond original specifications at that time. It was unused for about
the last 2 years and now when I listen to it, I get distortion in the audio
output at about 1/3 to 1/2 volume. The more I increase the volume, the
worse the distortion becomes.

What might this be a symptom of?

Thanks in advance for your advise and help.

Cal in TX Cal, I would first check the coupling cap from audio driver plate to output tube 1st. grid,,,It will probably be about .001uf.. change it...also look at the audio output tube cathode ,,,cap from cathode to gnd..maybe 10 to 20 uf. When the coupling cap leaks ,it behaves like a resistor, putting a DC voltage on output tube grid..output grid should be a neg v to gnd...when cap leaks the grid will become pos v..That is usually the problem....GL W4PQW