[ARC5] Command set BFO coil - is it affected by the can filler (beeswax?)

[Martyn Google]

I’ve repaired many of these caps and the main problem I see is the alum strips that contact the back of the tin plated brass pots are all dull grey corroded and fall apart presume it’s all turned to alum oxide thus non conductive. If you have a lathe it’s easy to turn off the mica top and resolder it on after replacing the caps & hard to tell from original.
Martyn ZL3CK
Sent from my iPhone

> On 28/02/2020, at 9:57 AM, Bill Cromwell <wrcromwell at gmail.com> wrote:
> 
> Hi,
> 
> I play accordions. The reed blocks are assembled using beeswax and resin but mostly beeswax. I have seen the steel reeds and other steel fittings inside accordions older than these radios and there is *NO* corrosion. Over the decades the wax dries out and the beeswax dust has to periodically be cleaned off from the reeds because it will detune them. Just as ordinary household dust does. But - no corrosion. Eventually the wax has to be removed and replaced due to drying out and losing it's seal.
> 
> Paper is made from formerly living material which eventually rots. I suspect the paper itself is why those caps fail.
> 
> 73,
> 
> Bill  KU8H
> 
>> On 2/27/20 1:41 PM, Scott Robinson wrote:
>> Folks,
>> The failure mode for paper capacitors starts with the fact that they are made from paper (not necessarily acid-free...) and tinfoil.  Over time, water vapor gets in, combines with the acids in the paper, and makes corrosion residues that are conductive, causing the capacitor to leak.
>> If the rubber seal get tired, as they will, the sealing action fails, water vapor gets in, and the above happens.
>> Without the paper part, the coils might do better. The failure mode will be for them to go open circuit, the copper having been attacked by water and/or acids from the beeswax.
>> FWIW,
>> Scott Robinson
> 
> 
> -- 
> bark less - wag more
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