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

[Barry Scott]

I'm not looking at an opened IF deck, but from the drawing of it, I'd
guess C523 is a Vitamin-Q cap and those are known to be pretty stable.
Of course, that cap could certainly be bad even if it is a Vitamin-Q
type.

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
>
>
> ______________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:R-390 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
> ______________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:R-390 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html