[ARC5] BC-348

[Richard Knoppow]

    I can also confirm how bad the Micamold paper caps are. Also 
Solar made similar caps. They have a white dot where the mica 
caps have a black dot. I restored an RCA AR-88F which had several 
Micamold  and Solar paper caps in the RF sections, all bad.
    I think these caps must have had some virtue when new. The 
caps in the AR-88 were in places originally speced for mica caps. 
During the war when these were built mica was in short supply so 
the paper caps were used in their place. I suspect the flat 
package had less parasitic inductance than tubular caps.
    This receiver also had oil filled bathtub paper caps. All had 
defective seals at the terminals and all the oil leaked out on 
the bottom cover. A PITA to clean. I replaced all with plastic 
caps, mounting the bathtub replacements on terminal strips. The 
AR-88 has no electrolytic caps, the power supply filter is an oil 
filled triple paper cap. That one tested good.
    I was warned about Micamold caps by my mentor who was a 
professional designer.
    Both Micamold and Solar vanished in the late 1940s, I have no 
idea what happened to them.

On 1/3/2020 10:39 AM, Whitebear1122 wrote:
> Thanks Joe and all for the clarification.  Yes I mean the 
> postage stamp paper caps in particular.  I misspoke by calling 
> them mica caps.  I owned a Micamolds XTR-1 transmitter at one 
> time and several of the Micamold postage stamp capacitors were 
> actually leaking droplets of oil.  I didn’t realize that those 
> Micamolds had such a terrible reputation.  73, Scott WA9WFA
>
>> On Dec 30, 2019, at 12:00 PM, Joe Connor 
>> <joeconnor53 at yahoo.com <mailto:joeconnor53 at yahoo.com>> wrote:
>>
>> Scott, do you really mean mica caps? Sometimes, there is 
>> confusion between notoriously unreliable Micamold caps and 
>> usually reliable mica caps. Micamolds are square .01 caps that 
>> look like mica caps but are actually paper. I replace them all 
>> because in my experience, the Micamolds are either shorted or 
>> about to short out.
>>
>> Here's a link to a site that has high-resolution copies of the 
>> various BC-348 manuals. BC-348s are fun receivers to work on 
>> and operate. That's great that you have the dynamotor, shock 
>> mount and Jones plugs because those things are becoming harder 
>> and harder to find.
>>
>> http://www.jamminpower.com/main/bc348.html
>>
>>   Joe Connor
>
>

-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL