[R-390] Strange variation of sensitivity AGC resistance toward the chassis

[Pierfrancesco Mengacci]

Hi!

 

In my former mail I complained a variation of the R390/A-URR  sensitivity. I
experience a slow variation, up and down, in all bands, unpredictable but in
some way related to chassis temperature (even 5 times from min to max
performance).

 

I must thank Larry, Roger, Jim and Cecil for suggestions on the matter.

 

I’ve been invited to control the efficiency of the AGC circuit, but,
apparently, it seems OK.

 

Just for scruple, does someone know which is the “normal”  value of the AGC
circuit resistance toward ground , measured at the rear contacts of TB 102
(n° 3 or 4), when the receiver is set on AGC function and disconnected from
power supply ? (AGC delay setting: medium)

 

In my case, I read 380 Kohm (when the negative terminal of the ohmmeter is
connected to the chassis, it has a minor influence...). This reading takes
even 5 minutes to stabilize.

 

 

Thanks in advance,

Franco