[ARC5] NC-270 Success

[Arden Allen]

> ..... I noticed when bringing up my 173 with a Variac that the background noise peaked at around 107 VAC input.  Above that voltage, the noise decreased.  In addition, the S-meter readings would peak at around 107 volts in.  I did a check using a General Radio 1001-A signal generator, on the 40 meter band, and sure enough there was a slight decrease in sensitivity with over 107 volts in.  Not much, but a decrease nonetheless, maybe a couple of dB at the most.  ..........

That sounds to me like a detector diode producing a lot of contact bias current that is driving the AGC bus negative.  Drop the filament voltage of the diode with a series resistor to see if that’s it when running the radio at over 107 volts.

Arden Allen
KB6NAX

He who is cruel to animals becomes
hard also in his dealings with men.
We can judge the heart of a man by
his treatment of animals.
—Immanuel Kant
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