Re: {Collins} Tough problem in 32S3 ALC semi-fixed



Grayson, Thank you. A heroic job of troubleshooting. My round emblem TX has some of the same problems.   Doug K6JEY



  

   On Monday, August 12, 2019, 8:17:21 AM PDT, Grayson Evans via Collins <collins@xxxxxxxxxxxxx> wrote: 
 
 To all of you who helped with my “tough prolem in 32S3 ALC”, wanted to let you know that I semi-fixed it.
I say “semi” because while it works, it is not satisfying.

I replaced every part in the ALC circuit including V6 (it is NEVER the tube).
I found that something past the ALC rectifiers was loading the ALC circuit.  
I seemed to isolate it to the part of the circuit that drives pin 1 of V6 through a 10K resistor R105.  When I lifted R105 from the ALC line, ALC was restored, not as much as in my winged 32S3, but enough so it worked OK.

I could not find anything in the grid circuit/tuned circuit that was causing the loading.  no shorts, opens, etc.  all voltages normal.  There isn’t much there.
10K in a grid circuit is a very low value unless collins was trying to kill two birds by using it to drastically lower the Q of the tuned circuit.
SO I replaced the 10K with a 470K.  I didn’t notice any difference in tuning, but this let the ALC work and deliver ALC voltage to V6 and V3.

I am tired of working on it so this will have to do for now.

Thanks all who helped.
73, Grayson KJ7UM

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