[R-390] Calibration Osc and 2nd Osc questions and AGC issue

[thoyer]

Well, it looks like my AGC issues may be due to the broken core in Z503. The
coil is fine, just the iron slug is in several pieces....
 
Last night I connected -9v to the AGC NOR terminal and traced the voltage
through various circuits. All measured voltages seem reasonable.
 
Once I locate a new slug I should be back in business.
 
Tom
W3TA

  _____  

From: Larry H [mailto:dinlarh at att.net] 
Sent: Monday, December 04, 2017 4:22 PM
To: Thomas Hoyer; bill.riches at verizon.net; r-390 at mailman.qth.net
Subject: Re: [R-390] Calibration Osc and 2nd Osc questions and AGC issue


Great work Tom.  Weak agc is usually leaky caps on the agc line.   C551 is
the large cap in the square can and not only does it leak like normal caps,
but it also leaks to ground.  Isolating the agc line is helpful by
unplugging units or removing the link on tb102.  Of course, a tube or z503
could be impairing agc gain.  Sometimes you need to remove the connection
from R546 to C547 to measure correctly.


Regards, Larry