[R-390] AGC problem

[Bill Hawkins]

Don't have voltages for you, but here are a few ideas:

Do you have the right tubes? No sharp cutoff where they should
be remote cutoff.

Does the S meter read correctly?

Do the resistors in the AGC circuit have the correct measured
values? How about the cathode resistors of the controlled tubes?
They should be within 20% of the schematic value.

Is the resistance to ground of the AGC line greater than 100 meg
if you isolate the line? Can you measure the resistance with
something that applies 20-30 volts to the line? Or just apply
voltage to the line with three 9 volt batteries and see if it
propagates down the line correctly.

Regards,
Bill Hawkins


-----Original Message-----
From: r-390-bounces at mailman.qth.net
[mailto:r-390-bounces at mailman.qth.net]On Behalf Of Bill Abate
Sent: Thursday, December 09, 2004 11:31 PM
To: r-390 at mailman.qth.net
Subject: [R-390] AGC problem


I also found the AGC voltage on all the tube grids it was supposed to 
control.  The only thing I can conclude is that the AGC voltage is 
insufficient but the manual does not say what the voltage should be with 
varying inputs.  At least I could not find it.  I also tried slow, med 
and fast AGC and the results were the same.

Anybody have data on the AGC line?  Any ideas as to the cause??

Thanks,

Bill, K3PGB