[R-390] 100K Resistor not in circuit.

[Larry H]

Hi Robert,  It sounds like the schematic I'm using.  The connection to the suppressor grids is supposed to keep the voltage from going very much plus at that point, like a clamping circuit.  This is an area in the agc circuit that does get modified for improved function on ssb, though.  See Dr. Lankfords 2-diode change.  There are others also.  It should not be that much + at that point.  It will mess up the agc and meter operation.  You might try swapping v504, v508, v509 and v506, in case they're faulty.  C551 usually goes bad and can cause this in 'agc slow' position, and other problems.  
Regards, Larry 
      From: Robert Ziolkowski via R-390 <r-390 at mailman.qth.net>
 To: "r-390 at mailman.qth.net" <r-390 at mailman.qth.net> 
 Sent: Tuesday, August 2, 2016 10:42 AM
 Subject: [R-390] 100K Resistor not in circuit.
   
I though the S-Meter circuit was not working properly in two of my R-390A's. When measuring the voltage on the 6AK6 V504, Pin 2 it was +4.2V, not -2.5V. Latest schematic I have shows it connected to another tube and a grid divider on V509A. Don't get the 125K or 280 k ohm reading that the Y2K-R3 or other diagrams show. It reads infinity. Don't want to remove the IF Module to see if it is wired like the schematic unless I have to. Is it possible the circuit has been modified in one of the updates? Thanks for your help.
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