[Milsurplus] BC-342-N Question

[W7QHO at aol.com]

In a message dated 6/2/07 6:55:29 PM, carolew at bellatlantic.net writes:


> I'm fixing up a BC-342-N and have a question. I see a black Micramold in 
> the 1st Detector Transformer can that I would like to change out. However, it 
> is located behind a board and seems virtually inaccessible. Has anyone found a 
> way to replace this cap? If so, how?
> 
> 
Joe,

Ah yes, those Micamold DBPCs (darn black plastic capacitors) so prolific in 
the BC-342 and other BAs.   High quality components for their time and FB for 
the first 30 years or so.   By now, though, if they haven't gone bad they will 
and in HV circuits they'll take out other components with them when they do. 
Cause nondestructive mischief in other places like AVC and audio coupling 
circuits too.   Only place I've gotten away with not replacing them is in low 
voltage filament circuits (BC-654 for ex.).    

I've had very few failures with the metal "bathtub" units in these sets, BTW.

Just went through a recapping job on a BC-342 here.   Sounds like you're 
talking about a DBPC in the xtal filter (1st. IF) can.   Actually two of these 
here, C54 in the plate circuit of the 6L7 and C63 in the AVC line to the first IF 
amp (6K7).   The exact placement of these two DBPCs can vary from set to set. 
 In my experience, however, the "hot" lead on each is usually exposed enough 
to get the dikes on it and the buried ground end lead can then be worried off 
with long-nose pliers or surgical forceps.   The removed components can then 
be replaced with modern units using alternate ground points.   I've been able 
to do all this without removing the IF can.  In my set, BTW, C54 WAS shorted 
and had taken R17 out with it.

You'll find two more DBPCs in the 2nd IF can, one more in the 3rd IF can, one 
in the BFO box, one buried down under the VOL dual pot, two in each of the 
three RF coil boxes, and one more in the HF osc. compartment (and I may have 
missed a couple) . Would highly recommend replacing ALL of these in the 
BC-342/312 sets.   To do this the RF coil boxes have to be dropped as Robert has 
described.   Bit of a job but not as bad as it sounds.

Hope this helps.

Dennis D. W7QHO
Glendale, CA



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