[R-390] AGC Troubleshooting

[Dennis L. Wade]

Thanks for the reply Roger.

	Good point.  7 meg may not indeed be a problem. But why don't I see the 
350K I saw from the AGC jumper?

	So let me review why think there is a problem:

		1.  With all modules connected, from the AGC jumper to ground is about 
350K.  When the RF deck is disconnected, it remains the same.  When the 
IF module is disconnected, it goes to about 1.8M to ground.  Does this 
isolate it to the IF deck?

		2.  I don't see more than about -4.9 vdc at the AGC jumper on very 
strong, or the cal, signals.  No signal is +0.15

		3.  There is distortion on strong signals.

	Note that I have not re aligned the receiver yet, I still have some 
caps to replace in the AF deck.  I'd like work on the IF deck if I need 
to while I have it out.

	Two basic questions:  Do I have an AGC problem given the measurements 
above?  And, is it isolated to the IF deck?

              Dennis


		

Flowertime01 at wmconnect.com wrote:
> Dennis,
> 
> I took out the IF deck and measured resistance from pin 6 to ground, and I 
> see about 7 meg with no charging behavior. it says I should see infinite 
> resistance.
> _____
> If you were doing this in 1970 with a TS 505 or a TS 352 on the K ohm range, 
> 7 meg would be infinite resistance. You are likely OK on this test.
> 
> TM 11-5820-358-35 8 Dec 1961 Para 72 b. Alignment of Z503 Page 113.
> says AGC should be in the range of -1 to -2 volts
> 
> My mail only goes back 5 days, so I do not have your original problem
> with your AGC.
> 
> Watch the other responses and keep asking questions until you
> feel you and your receiver are happy.
> 
> Roger KC6TRU
> 
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-- 
--------
Dennis L. Wade
KG6ZI
Carmichael, CA