[R-390] AGC Problem Fixed :))

[Dennis L. Wade]

Good Afternoon,

	The nagging not-quite-right AGC line in my Motorola '390A has been 
fixed.  The culprit:  V509

	Got out to the garage early enough to avoid the heat and took some 
voltage readings on the signal grids of V501, 502 and 503.  All were 
slightly *positive* under no signal conditions.  Pin 2 of V509 was also 
slightly positive.  In my research through the Pearls (many, many thanks 
Wei Li), I kept seeing posts from Dr. Jerry that said in 
essence...positive grids are either from leaky caps or gassy tubes. I 
wasn't finding any strong evidence of leaky caps.

	So, almost on a lark, I swapped V506 and V509.  Voila!!  Negative grids 
return.  Hooked up an antenna...noticeable improvement in audio quality. 
  The offending tube does not test gassy on my emission type tester 
however, although that doesn't surprise me.

	So, Roger, your advice was sound..that is...go on with it and finish 
the radio.  And I was...but after just oneeeeeee more thing to try.

	Thank you all for your help.  I'm sure you'll hear from me again 
shortly as I continue on.   :)

               Dennis
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Dennis L. Wade
KG6ZI
Carmichael, CA