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
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 <[email protected]> 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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