[R-390] R-390 (non-A) - Low RF Gain or bad Antenna relay?

[Barry Scott]

That resistance measurement seems quite odd.  R536 is supposed to be
820 ohms.  Unless C523 is bad, I don't see how there should be
anything much less than 820 ohms at pin 7 of V506 yet the resistance
diagram shows 700 ohms.  99 ohms seems very wrong.

Thanks,
Barry - N4BUQ

On Wed, Nov 6, 2024 at 8:12 PM <k1jos at att.net> wrote:
>
> Update....
>
> I checked voltages and resistances per TM  11-5820-357-35 (09 March 1962) for the IF amps V501 - V506.  I don’t know if my R-390 had any mods, its SN 1256, but all the results were very close to the listed values except for V506, 6th IF amp.  The cathode should read  700 ohms to ground and 8.2vdc and I find 99 ohms and 2.3vdc.   The schematic shows the cathode bias resistor of 800 ohms and a 15ohm pot for carrier meter adjustment.  There is a decoupling cap 0.1uF off the cathode that if leaky could bring the resistance down to my reading.   But would this be enough to drop my gain so dramatically?
>
> Jerry
>
>
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