Has anyone run into a problem with intermittent tube socket contacts on an
R-4(*)? I have an R-4A that apparently makes intermittent contact on a
pin or pins of V4. When first turned on the receiver works fine but after it
runs for a while an S-9 signal will suddenly drop to S5 for a moment or
two, then jump back up. Diddling with the pins from underneath using an
insulated wand will make the signal come and go but I see nothing loose and no
sign of a cold solder joint (not that appearances always show them).
I used Deoxit on the pins and even used a round toothpick with the tip
soaked in Deoxit to "spin" by hand in each pin to remove residue. I tried
a couple of different tubes and even cleaned the tube pins with Deoxit but
it's still flaky. I tried making the pin sockets a little tighter by
gently pressing the sides in but the problem persists. I also loosened and
re-tightened the screws that hold the socket down to ensure decent grounding.
(NOTE: The chassis of this R-4A is quite shiny, in fact remarkable
condition, so I'd be surprised if corrosion is a problem).
My next approach will be to re-heat all of the pins to eliminate any
cold joints and also to reheat the connections on the PCB that feeds those
pins.
Any other suggestions welcomed - and yes, I do need to measure
voltages (B+, etc.) on the tube when the signal drops and will do so tonight.
73/arf,
Paul, K4MSG
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