No Variac Warning! Re: [sdiy] Lifespan of Electrolytics?

[Jim Patchell]

    Actually, there is nothing to worry about.  When you have a power
supply that is starting to get into the 1KW range, being able to bring it
up nice and slow the first time is a pretty smart thing to do.  In fact,
I use about a 250W variac to do this (but not while drawing 1KW).  If the
variac begins to groan, you know you have a serious problem and had best
try to discover what is wrong.  Something that can supply 1KW ( and more
is even worse) can generate some really cool fireworks, but the safety
people get really upset when you set off the smoke alarms.

    It is perfectly safe to run a transformer winding up to its rated
voltage.

    -Jim

Cynthia Webster wrote:

> Hi
>
> I wouldn't advise using a Variac with anything using a transformer!!
> (Variac to transformer = Heap Bad Mojo)!
>
> DO NOT TRY HIS AT HOME!
> (well, maybe in the kitchen if you have a nice apple pie in the oven)
>
> Seriously folks
> The windings of many a transformer are simply not designed for
> anything other than a standard mains supply from the wall.
>
> Playing with the voltages or frequency of the voltage is not advised!
> Bringing a power supply "up to operating voltage" with a Variac is
> much more likely to cause problems - than to solve them...
>
> There are a few electronic speed controls that may work,
> however the majority of them do not.  So be warned!
> This applies to florescent light ballasts (transformers),
> and most motors as well.
>
> on 5/20/02 11:22 AM, Tim Ressel at madhun2001 at yahoo.com wrote:
>
> > Yo,
> >
> > I have heard tales of woe concerning electrolytics.
> > One story is that if they are run with a significant
> > percentage of the working voltage, something bad will
> > happen. I'm not sure I believe that. Another concern
> > is electrolytics that have not been used for a long
> > time. The electrolyte 'goes bad' somehow. You're
> > supposed to bring the voltage up slowly when firing up
> > a unit after a long idle period, to 'reform' the
> > electrolyte.
> >
> > I have had none of these problems. However, when I
> > received my used Heathkit tube power supply, I brought
> > it up slowly with a variac, just to be safe.
> >
> > Does anyone have a circuit for testing caps??
> >
> > --TR
> >
> >
> > No Variac Warning!   Re: [sdiy] Lifespan of Electrolytics?