[Amps] Silver Epoxy Needed

[Roger]

RICHARD SOLOMON wrote:
> I have a 200 pF 10 KV Doorknob that has one end broken off.
>
> It looks like Silver Epoxy was used to fix the terminal to the cap.
>
> Correct me if I am wrong.
>
>   
I used to use a lot of these transmitting doorknobs in high powered 
systems to adjust frequency.  It was not uncommon to blow them apart. 
All that I "swept up" had been soldered..

This following is what I'd try, but comes no guarantee  as these things 
are relatively fragile.
I think you will find a small "toaster oven" will get hot enough to melt 
solder. I'd prefer something a bit more precise, but you need to bring 
the whole device up to temp over a few minutes, let back for just a 
couple, (just long enough for all the solder to melt and the end to 
settle in place), and then cool down over half an hour to hour.

I'd build a small fixture to hold it vertically.  The ends IIRC are 
threaded for 10-32. so the fixture need be nothing more than a small 
metal plate with a 10-32 screw through it into the one end of the cap.  
screw the loose end to a steel plate/weight/nut of about 4 or 5 ounces. 
It  needs just enough to help settle the end when the solder melts.

Although written out it sounds complicated, it's quite simple, but coefficients of expansion being what they are the results are unpredictable.  IIRC these things were soldered using an relatively high powered induction heater that just applied a burst of power so the soldering only took a few seconds at most.  

We also used some identical looking spark gaps across the system, but the used Cesium to set the ionization potential. I had one of those fall apart in my hands.  Ever spend half an hour in a cold shower getting decontaminated? <:-)) (They were hot enough we had to have a license for them)

Some one mentioned JB Weld which would probably work although I think the value and current handling capability might be changed.  OTOH as it stands it's no good now so you have nothing to lose by experimenting. Just be careful if using heat as the ceramic sometimes shatters. Wear gloves and safety glasses.

73

Roger (K8RI)
> Where can I locate a small amount of this material to repair this
>
> cap ?
>
>  
>
> Thanks, Dick, W1KSZ
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