[NJARC] Deactivating AVC on Atwater Kent Radio?

[Al Klase]

Hi George,

Long time. No see.

I don't know this radio at all, but I read schematics pretty well.  WHAT 
A FREAKIN" NIGHTMARE!

I'm working from Rider's  A.K. page 1-59 and the voltage chart on 1-56. 
(From nostalgiaair.com)

Try disconnecting the grid of the control tube, and connecting it to the 
low side of the volume control ( junction with the 670 ohm resistor that 
goes to ground.  This should disable the AVC, and still allow the volume 
control to control the control tube.  (Does the work control appear 
often enough in that sentence?)  If that doesn't do the trick you might 
try connecting the grid to ground..

I'd also take a careful look at the 1st det. and I.F. tubes in terms of 
cathode to filament leakage.  The cathodes of these tubes are being 
operated way above ground, and leakage could cause strange problems.

See if that helps.

Regards,
Al

On 10/24/2011 8:04 PM, George B. Shields, Jr. wrote:
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> _________________________________________________________
>
> Hi All,Still working on a 1931 AK82 cathedral with the "infamous" control tube with AVC. I have completely rebuilt the resistor network and cleaned the volume control.  I have swapped out the controal tube (UX224) THREE times and have replaced all of the bleeder resistors.  There has been very little if ANY improvement in the volume instability in the set.  The voltage across the resistor network to which the volume control is connected fluctuates between 21 and 19 volts at "normal" listening volume.  Now, this is more than sufficient to drive the control tube from little volume control (unbearably loud) to full cutoff and back again seemingly whenever it wants to.
> So, I have read several comments about how bad this primitive AVC / volume control arrangement actually was in practice and that it can be circumvented, thereby rendering the volume control much more stable in daily operation.  But how do I do it??????  Can someone who has worked with this condition tell me what needs to be done to bypass (or otherwise deactivate) the AVC circuit so this set will operate with more stability when tuned to a station?  Other than accounting for the normal minor voltage fluctuations which exist in the AC line current in my home, I cannot find anything in this set which would account for the significant fluctuations in the resistor network (and yes, one-two volts represents a MAJOR fluctuation of voltage in this circuit!)
> Ideas welcome!
> -George-
>
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-- 
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/