[ARC5] Carbon Composition Mug Shots

[CARL HUETHER]

You never know with carbon comps and IMO they are always worth holding onto if into vintage work or duplication in a new project. Some Ive had since the late 50's when I used scrapped radios from the town dump or at the curb for parts. Old 30's dog bone styles are easy to repaint with standard colors close to the value measured.....my experience is they have stopped drifting after 70-80 years or so.  Restuffed paper caps add to the original look that some want.


Allen Bradleys are one brand that seems to hold up well over time and there are several other unknowns that are equally good.  Just yesterday I pulled an unknown 15K 1W 5% out of stock that measured 15.6K. It was a 40's era style and just right for the customers radio who didnt want modern looking parts.


On a side note National had a mismarked batch of 47K 1/2W in the 50's that were actually 470K. These were used as screen droppers and with 3 IF's and a selected cathode resistor as shown on the schematic as * they would easily make stage gain specs. With only 2 IF's it was cutting it close and likely the reason for many tube swaps as they aged. Having worked as a Service Tech at National in the 60's it saved me a lot of grief in later years.


Carl



> On March 3, 2019 at 11:05 AM J Mcvey via ARC5 <arc5 at mailman.qth.net> wrote:
> 
>     have included a picture of three components that  have recently replaced in radios:
> 
>     The 47K looks perfect in every way, no sign of running hot, yet is is open.
> 
>     The 27K looks like it ran warmer, but it is now a 70K resistor. Both of these came out of the same early 1970's transceiver.  Looks like there may have been a bad batch of 2W resistors in that run...?
> 
>     The third is the infamous 'guaranteed to leak" "black beauty" capacitor. This is one of a dozen I removed from an old receiver.  All of the ones I tested were bad.
> 
>     Jim, AC2EU
> 
> 
> 


 

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