MR-1 distortion on strong SSB signals - HELP!

[Gary Schafer]

Hi Sandy

Sounds like it could be a leaky bypass cap somewhere on the avc line. Also could be some
grid leakage in one of the rf or if amp tubes that the tube tester doesn't show.

73
Gary  K4FMX


Sandy Gerli wrote:

> Hi,
>
> Going through my MR-1 which seemed to work all right, I noticed that
> some feller had removed the 8uF/475V cap at the B+ input and also
> had disconnected the 750 ohm 10W dropping resistor. Hmmm...I
> restored the configuration to normal. Now, I notice that, on strong
> SSB signals, there's considerable audio distortion which goes away
> if I crank the RF Gain way back. Perhaps Joe Ham had low B+ and was
> trying to jack it up a bit. Anyway, I'm using an HP-20 with the
> correct voltages.
>
> All other alignment parameters seem just fine; I went through the
> whole procedure. What's left is this distortion and a weak S-meter.
> That takes a 1000mV signal from my HP sig gen to get an S-9 signal.
> Supposed to be 100uV for S-9. All tubes check out well.
>
> I suspect something in the AVC line, but I'm not sure where to
> start. That 6T8 triode/triple diode is an odd duck on the schematic.
> It's hard to tell from the envelope diagram WHICH section is the AVC
> rectifier, although I suspect it's off Pin 2, going to the AVC buss
> through several high-value (2.2 meg and 1 meg) resistors.
>
> Anyone have any suggestions?
>
> 73,
>
> --
> Sandy Gerli, AC1Y
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>
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