[ARC5] Mica Capacitor

[Dennis DuValll]

Yep, the old DBPCs (darn black plastic capacitors).  Always bad, replace all going in.  I have gotten away with leaving them in place bypassing the low voltage filament circuits in the SCR-284.  Dozens of them used for that in the radio, all hard to reach… :^(
Replace in all other circuits though.

Dennis D.  W7QHO
Glendale, CA

****************





> On Sep 17, 2016, at 1:38 PM, Sandy <ebjr37 at charter.net> wrote:
> 
> This is the "gospel truth"!  Ask the real old timers who dealt with "Moulded paper" (alias: MICAMOULD) capacitors!  absolute trash, short shelf life.  Anyone who has "recapped" an old SCR-522 transceiver or some BC-312, BC-342, BC-348 receivers will attest to this.  Drove SCR-522 radio rebuilders nuts.  Even on brand new unused gear!
> 
> 73,
> 
> Sandy W5TVW
> 
> 
> On 9/17/2016 2:36 PM, Richard Knoppow wrote:
>>   A note: The charts will show a color dot on some flat type caps which is either white or silver,  or black. Black is for mica, white or silver for paper. One may encounter flat paper caps in some older equipment, they were made by Micamold and Solar, maybe others. They should replaced. They may have been high performance when new but suffer from the same ageing problems as other paper caps.  They were sometimes used in place of mica caps in less critical applications during WW-2 when mica was in short supply.  Plastic film caps are good replacements and probably superior to the originals when they were new.
>> 
>> On 9/17/2016 12:10 PM, WA5CAB--- via ARC5 wrote:
>>> Those charts are in most of the TM 11's printed from 1942 or 43 into the
>>> mid-1950's.
>>> 
>>> Robert Downs - Houston
>>> wa5cab dot com (Web Store)
>>> MVPA 9480
>>> 
>>> In a message dated 09/17/2016 10:44:17 AM Central Daylight Time,
>>> releazer at earthlink.net writes:
>>>> Ken:
>>>> 
>>>> Okay, I found the mica cap color codes in a copy of TM11-630. I had
>>>> no idea
>>>> there were so many kinds.  Anyway, I decided that the codes on the
>>>> mica cap
>>>> matched the American War Standard, and equate to 0.01 mfd bypass cap,
>>>> 500V.
>>>> It's not too hard to find a ceramic disk cap with those values!
>>>> 
>>>> By the way, I scanned the cap color code section out of that TM and if
>>>> any
>>>> one wants a copy I can e-mail it to you.
>>>> 
>>>> Thanks!
>>>> 
>>>> Wayne
>>> 
>>> 
>>> 
>>> 
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> 
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