TU56/TC11 restoration - VARIAC question

[O. Sharp]

Ashley Carder wrote, in part:

> Based on all the info that you and others have provided,
> it looks like an option is to remove the capacitors from the unit and hook
> them up directly to the variac.  Or is that not the right thing to do?

Maybe I've become confused along the way - it's definitely happened 
before <g> - but if you're looking at reforming electrolytic capacitors, 
I believe hooking them directly to the variac is definitely _not_ what 
you want.

The idea is to feed the cap a trickle of DC current to get all the happy 
little electrolytes to slowly rebond themselves to the capacitor's 
plating, and as you get part of the cap restored you can then apply 
greater voltage so more rebonding can take place until eventually the 
capacitor is reformed to its full rating. There seem to be two standard 
ways of doing this, which may perhaps be creating some confusion since 
it's not always obvious which is being discussed; so for clarity I'll 
arbitrarily call them the bench method and the variac method.

(Note to rest of list: if I basically screw up all the details on this, 
please tell me. I'm still new at it myself. <g>)

The Bench Method: Remove the capacitor, hook it up to a variable-voltage 
DC bench power supply, find a way to limit the amount of current (either a 
current-limiting power supply, or a big fat resistor), and slowly (e.g., 
over the course of several long hours or days) turn the voltage output up 
on the power supply:

Mains --> DC Power Supply --> Current-Limiting Resistor --> Cap
      ^-AC                ^-low-voltage DC              ^-low-current DC

The Variac Method: Since cap reformation is usually an issue with old 
power supplies, and the power supplies are specifically converting AC 
voltages to DC, you can use the variac to supply the entire unit with 
ridiculously low AC voltage and let the power supply figure it out for 
itself. The variac voltage is gradually turned up over hours or days as 
before, and the capacitors in the old power supply all reform from the 
same source. (Doing this means one should also disconnect the power supply 
from the rest of the equipment, and put some sort of dummy load in its 
place, so you don't inadvertantly fry your classic equipment.) 

Mains --> Variac --> Old Power Supply --> Caps
      ^-AC       ^-low-voltage AC  ^-converts to DC internally

The variac method is a little easier because you don't have to dig all 
the caps out of the machine, and you can skimp on the math; but it's less 
precise, harder to monitor and has the capacity to destroy more equipment 
much faster. I've done it once, and it worked, but as I've learned more I 
don't think I want to try using that method again.  :)

> Excuse me if I'm asking dumb questions, it's because I'm learning as I go.

Yeah, well, as my numerous disclaimers above may indicate, _I'm_ sure as 
hell no expert.  :) :) :)

                     -O.-