[Collins] 51J-4 1st IF problem

[Mark Croney]

I am working on a 51J-4 problem and I thought I would share this with the
group and see if anyone can offer some insights.

 

The symptom is that there is an intermittent rise and drop in signal
strength.  While listening to what should be a steady signal, the signal
strength meter can jump to different signal strengths intermittently.  

 

I also notice that V301, 1st IF Amplifier, can be wiggled in its socket and
make similar changes in signal strength occur.  When I push V301 all the way
into its socket, there is a strong oscillation that occurs.  I have to pull
the tube up from the fully seated position for the receiver to function
normally.  I've swapped tubes with no change in performance.  I've also used
some Deoxit on the tube socket with no change.  I am suspecting some of the
mica coupling capacitors underneath that are house within the module where
the mechanical filters are mounted. 

 

Has anyone had a similar experience?  Also, If I do have to obtain access to
the inside of the mechanical filter mechanism to access these capacitors,
what's the best way to do that?  

 

Thanks,

Mark

W4ZF

 

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