[Milsurplus] BC348 out of storage

[Dale LeStourgeon]

A few years ago I acquired an un molested BC-224C without 12v dynamotor . It needed cleaning and I made a nice power supply. It was working FB but everyone said replace the micamolds ( I had done this with BC-348s). I took them out and replaced them with new caps . The radio worked the same.  I cracked open one of the ones I had jerked out and to my chagrin, it was perfect mica  inside. I checked the other pulls and they were right on.01. The radio seems to have been made in1939. Has a bronze tag even. Wish I had known.Dale K5AJZ


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On Monday, August 4, 2025, 3:37 PM, jphutch60bj <jphutch60bj at gmail.com> wrote:

Thanks for the inputs!  much appreciated.

Its not a general bypass cap issue, as most of those 0.01 have been 
replaced in a large part in both units and the 0.05 oils with orange drops.

     The power draw is nominal range at 227 Volt range at the terminal 
block.  No smoke or other any other oders. ++

I will check the  Tuning Cap :

          Back lash gear and put some deoxit on the wipers.

One Unit has a bad band will have to do some surgery  to fix that.

Thanks

JPH


On 8/4/2025 1:35 PM, hwhall--- via Milsurplus wrote:
> Micamold did make real mica capacitors. Pre-WWII Micamold made mica caps in sizes from pF to as large as 0.02 uF. They started making lots of paper caps during WWII because mica was considered a strategic mineral resource. Afterward the war, it was just an accepted & cheaper method. And Micamold wasn't the only manufacturer who put paper-insulated caps into what looked like tabular mica capacitor bodies.
>
> The most likely to be paper seem to me to be the black bodied rectangular ones with beveled corners and/or edges. Small brown square-cornered ones seem most likely to be mica internally. Low picofarad values are also more likely to be real mica. Location in the schematic is also a tip; caps used in RF & IF tuned circuits are more likely mica, audio & bypass caps more likely to be paper.
>
> The attached Micamold advertisement (1954) hints at shapes that can be used as clues, with the exception of one body shape that it shows was used for both mica & paper.
>
> Wayne
> WB4OGM
>
> On Monday, August 4, 2025 at 11:38:28 AM MDT, kgordon2006 at frontier.com <kgordon2006 at frontier.com> wrote:
>
> On 3 Aug 2025 at 22:15, Charlie L. wrote:
>
>> The old mica postage stamp caps are known to go bad in all the removable modules,
>> and they can contribute to instability in the HFO and BFO stages.  If it has those large
>> Micamold caps on the terminal boards, I guarantee those are bad and causing issues.
>>
>> Charlie, W4MEC
> Those cursed "MicaMold" flat, usually dark-brown, plastic-cased, capacitors are total and
> complete pieces of garbage. Every single one of those I have ever tested were bad. ALL
> leaked like a sieve, some were dead short.
>
> And there is absolutely NOTHING "mica" about them: they're simply squashed flat paper
> caps.
>
> Total junk.
>
> Get rid of every single one you ever find anywhere in any radio.
>
> Ken W7EKB
>
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