[Boatanchors] BC-348 Manual Comments and Stuff

[Joe Connor]

Yes, Scott, those military manuals are excellent. Think about it for a minute. A lot of the guys who worked on these sets during the war weren't experienced technicians. They enlisted or were drafted, and then quickly trained. Comprehensive manuals were a must. 
You can really see how good the military manuals are when you take a set with a civilian counterpart, like the SX-28, and compare the military manual with the civilian manual. There is no comparison.
Those .01 micmolds are really bad. Interestingly, I worked on an R-45/ARR-7 that had micamolds that were .0082, not .01, and might have been made of mica because they all tested good. It surprised the hell out of me because I was used to the horrible micamolds in the BC-348s.
There are several techniques for mounting the new caps. I've found that .01 ceramic disks mount very nicely on those boards, but the yellow ones mount almost as easily.
            Joe Connor 

    On Tuesday, November 28, 2017 11:56 PM, Whitebear1122 <whitebear1122 at comcast.net> wrote:
 

 I downloaded a BC-348H manual from the BC348 page on Jammingpower and printed it out.  Tonight I was going through the manual to find out how many 0.01 and 0.5 mfd  paper caps to order. 

I am so impressed with this radio manual. I was expecting some worthless manual due to the urgency of World War II but instead I found a well written manual with clear photos of each resistor/capacitor board and assembly with clear references to EACH component,  board diagrams, circuit descriptions, alignment, and schematics.  Even the parts list was easy to use.  With each turn of the page I would find myself thinking of the urgency of the people designing the radio, the component manufacturers, the radio manufacturers, in the time of desperation.  This was a radio that had a very short anticipated lifetime.... in a B25 bomber heading off to war, either to return to fight again or get blown out the sky.  It is an odd feeling.  

I’ve never seen that technique before where each component is given a reference number that makes it so easy to locate in the parts list.  Number like 32 or 32-1, 32-2, etc.. I would see a component with a reference of, for example, 11-1 or 11-2 and be able to quickly find it in the parts list where each part is identified separately, and not buried in a rows full of R1 through R100 numbers.  Like the radio, the manual was also well thought out.

So the replacement capacitors are on order with our friends justradios.com for those pesky Micamold paper capacitors.  I am reminded of a Micamold XTR-1 transmitter that I once owned.  I opened it up and was surprised to see several of the Micamold capacitors with a big oil drop on the case.  It was the dielectric leaking through the case.  In spite of our modern day crabbing about the quality of the capacitors, I’m sure no one of that era had even a clue that these radios would be in use 70 years later.  Hell I think the anticipated lifetime of a BC-348 was in months, not 70 years :)

Bill W2DGB suggested a mounting method to clip the caps and mount new ones to the tube sockets.  I’ve been looking at the resistor boards and it looks like I can at a minimum clip one end of a hidden capacitor and then solder the new ones on the topside of the resistor boards where the solder terminals are easily accessible.  

For you guys that recapped all the paper capacitors, did you use this technique or the W2DGB technique, or unsolder wires and remove the resistor boards completely and do a capacitor AND resistor change out?

73, Scott WA9WFA

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