[Collins] Help with my 51J-4 - Ser. No. 2954 Please

[Kurt Brandstetter]

Hello from Vienna !

I have a problem (or I think I have one) with my Collins 51J-4:

If I switch the receiver on the following values of AGC I have:

NO antenna connected, RF sensivity full clockwise (highest sensivity):

AGC: - 1.65 V; BFO OFF
AGC: - 1.70 V; BFO ON

After 2-4 hours of operation the values are:
BFO OFF: 
AGC: - 1.75 V

BFO ON:
AGC: after 2 hours: - 2.5 V; 
AGC: after 3-4 hours: - 4 V; if I operate longer this value does not change
any more.
BFO ON (S-Meter reading about 25-30 dB RF), AGC measured at the AGC out on
the rear of the receiver.

This possible failure occures not suddenly; the AGC rises slowly in the 3
hours.
In AM all is working ok as the BFO is off. It occures on all bandwiths with
the same values.

Not a big problem, because I want to listen to SSB I swith AGC off and
regulate the reciever sensivity with the RF gain.

Can someone give me some hints where to look (I have not checked ths tubes
until now)
But I want to find the failure if possible for me.

TIA
Kurt OE1002419
-- 
73 de Kurt OE 1002419          ICQ-UIN 43074273
CCA member AC01-01249 NCDXF #4175  INDEXA #1720 
Homepage: http://www.swl.net/oe1002419   
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