[Milsurplus] BC-348-J BFO Help Needed (Corrected)

[AKLDGUY]

This is exactly the problem I had with my 3-6 Mc Command receiver BFO. I
changed tube, dismantled the coil, replaced the grid leak resistor, and
still the BFO would refuse to operate until I touched the grid leak with a
screwdriver. The problem proved to be the mica grid leak capacitor (100
pF). I suspect it went open circuit and the screwdriver provided just
enough capacitance to bring the BFO to life until next switch off. The BFO
played perfectly after replacement with a new 120 pF mica unit that was
left over in my junk box from an abandoned project.

Neil ZL1ANM


On Thursday, January 3, 2019, Joe Connor via Milsurplus <
milsurplus at mailman.qth.net> wrote:

> Guys, I need some help and advice for a BC-348-J I'm working on. The link
> for the manual is below (AN 08-10-112) and the schematic is on pp. 75-76.
>
> My problem is no BFO. With the BFO switch on, the voltages look pretty
> good, but no BFO. While I was doing the voltage testing, I found that when
> my probe touches the grid (pin 2) of the 6SR7 (2nd Det/CW Osc.) with the
> BFO switch on, I get the BFO loud and clear. With the probe on but the BFO
> switch off, I don't get the BFO tone.
>
> Any ideas? From the results above, I assume I can rule out the BFO
> oscillator, the 6SR7 and the BFO switch as the culprits. What else is there?
>
> This receiver is pretty nice. No mods and I have the shock mount, so I'd
> really like to get it going full blast.
>
> As always, thank you for your help.
>
>                             Joe Connor
>
>
>
> http://bama.edebris.com/manuals/military/bc348/
>
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