[MRCA] Working on an old BC-342

[David Olean]

Hello folks and thanks for the advice on the BC-312/342. The oil filled 
caps in the BC-342 are rectangular and soldered together. Luckily they 
are all located in HV  B+ lines and are not in the AVC circuits.  They 
are working for now in my radio.  I will try the big soldering iron idea 
first to remove the covers. If that does not work very well, I can saw 
the cap apart just under the top cover. That will require removing all 
of the caps though. Once sawed in two, the top cover can be re installed 
on the capacitor body and the only difference will be that it is a bit 
shorter.

I did dis assemble the radio by unsoldering all of the RF coil and the 
oscillator compartments and swapped out all those Micamolds that were in 
the AVC line in those boxes. I put the radio back together and the set 
really took off. As the tubes warmed up, I was greeted by a very ample 
supply of background noise on all bands.  The set is not hot as a two 
dollar gun. I checked the 6 dB S/N ratio at 5 MHz and saw 0.26 
microvolts for a 6 dB jump in audio. A 1 microvolt signal is now loud on 
all the bands.

My plan is to give the radio to my grandkids and hope they get a kick 
out of snooping around on the air waves.  At a minimum, it will get some 
attention.

I also did some snooping around and found a very early article by George 
Grammer back in Septemer of 1946 on the pages of QST. His article is 
great and covers many items that need work to improve the radio. Sadly, 
many subsequent articles are around that have plagiarized the original. 
Some parts of the texts are copied almost word for word.  Pretty sad. 
There is never any ref back to George's original work.

73

Dave K1WHS





On 2/16/2025 9:05 PM, J Mcvey wrote:
> That's a whole lotta extra work. But if you MUST:
>
> Try carefully cutting the insulator face as close to the metal body as 
> possible, and pry it off , cut the internal wire and remove it , Scoop 
> ior drill the capacitor out. Stuff with a metal film type that should 
> be small enough to fit.
>
> Plan B: Cut in half with a pipe cutter.and remove innards , stuff it, 
> solder the two halves back together.
> One of those two ways will probably get it done, whichever seems the 
> path of least resistance.
>
>
>
> On Sunday, February 16, 2025 at 02:23:20 PM EST, David Olean 
> <k1whs at metrocast.net> wrote:
>
>
> About 2 or 3 years ago I bought a slightly re worked BC-342 at Gilbert,
> PA and just got around to trying it out. Lo and behold, it actually
> worked. On closer inspection I found that it had issues. The cursor in
> the frequency window was made from a chunk of #12 copper house wiring!
> I forget who sold it, but the price was right and I figured it would be
> fun to get it going. I read two nice articles about the BC-312/342. Mine
> has the RA-20 AC supply and it had sensitivity at about 2.5 microvolts
> for maybe 10 or 15 dB S/N ratio. According to data that i saw, it was a
> bit deaf. It also overloaded and the oscillator pulled on strong
> signals. I figured that the AVC was probably messed up. I then read that
> there were a few Micamold paper caps inside the RF coil compartments.
> Getting them out of the RX is a chore requiring some serious un
> soldering, but I bit the bullet and started on a re build.  Yes there
> were Micamolds in the RF compartments, but when I looked in the IF cans
> I found 0.01 MFD mica caps that had absolutely no leakage.  The article
> that I read in Electric Radio mentioned paper caps in the IF cans too. I
> did not see that and left the mica caps in there. So I have been
> swapping out the paper caps in the LO and all of the RF and the 1st
> detector stages. Each and every paper cap was quite leaky, so I am glad
> I dug into it. That leaves the metal encased bypass caps left to deal
> with. My plan is to use a big (I mean BIG) soldering iron and gently pry
> off the tops of each can and then dig out the guts, replace with new
> mylar caps and then re seal the cans. I read that someone tried to open
> them with a gas torch and almost burned down his house as the oil caught
> fire.  If I can't pry open the caps, I need a Plan B. Is there a good
> way to replace those metal can caps and still have it look sorta original?
>
> 73
>
> Dave K1WHS
>
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