[MRCA] Working on an old BC-342

Mon Feb 17 13:50:26 EST 2025

 Oh you have the "tubs"!  Take it outside, drill a hole in the bottom plate. Hold it With a pair of tongs, heat the bottom over a metal can with a torch. The oil will leak out,  but may flare if you over heat it..The drilling is optional, but maybe a little safer.Apply heat around the edges and the solder will  liquefy and drip off. once the solder has dripped off, rap the tub against a fireproof solid surface. The bottom cap will usually fall out. Occasionally you may have to pry it off while heating. Gut it, etc, etc.I think it would be a very slow process trying to unsolder that cover with even a BIG iron.

    On Monday, February 17, 2025 at 01:21:47 PM EST, David Olean <k1whs at metrocast.net> wrote:  

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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