[ARC5] Use of a Variac

[Robert Nickels]

On 4/23/2020 6:08 PM, Mark K3MSB wrote:
>
> Very nice video.   To test capacitors I do pretty much the same thing 
> with either my Heath capacitor tester or HV power supply and some 
> meters.   You have nudged me to build a meter box like you did.
>
Just to clarify, it wasn't my video, I just liked the re-forming box 
"that guy" made.   I should make one like it but I'm lazy and just use 
the Sprague.

If I'm rebuilding a transmitter,  I would simply not feel good about 
putting in 30+ year old caps (reformed) when a short after hours of 
operation can take out something made of unobtainium

Agree fully.  As I stated, I do re-forming when a piece of equipment is 
new enough that the filter capacitor electrolyte likely hasn't dried 
out, but which hasn't been powered-up recently enough to be sure that 
the aluminum oxide dielectric if fully formed.   Time and lack of 
voltage is the enemy of all electrolytics, even NOS ones still in the 
box, and indiscriminately applying full voltage to a capacitor where the 
dielectric has started to deteriorate is likely to result in voltage 
breakdown, accompanied by heating and outgassing or even explosion.    
Re-forming basically repeats the final stage of capacitor manufacturing 
where the dielectric is initally formed to create a uniform dielectric 
layer in a capacitor that is otherwise still viable.

CE Manufacturing makes electrolytics using the original P.R. Mallory 
equipment and while the whole process might be of interest, I would 
direct those wishing to understand the process of how newly-made 
capacitors are formed initially to Step 8: 
https://www.cemfg.com/can-capacitors

There's also a set of videos; in the video CE Mfg. ages up to 100 
capacitors at a time for four hours with 540 volts applied (I assume 
these are those sold as 525V DC rated).

73, Bob W9RAN