[sdiy] outlet as variac? calling all EEs...

[The Peasant]

>okay, here's a weird question.  i've got an old apartment that has kinda
>weird wiring.  there's an outlet in the living room that's on the light
>switch, but said light switch has a dimmer on it.  this has always been
>annoying for me because to use anything on that outlet, you have to turn the

>lights on full bore, regardless of available light.

DO NOT run electronics of any kind on sockets wired with dimmers! This is very
bad practice, a dimmer should only ever be wired to a dedicated lamp fixture.
I recommend replacing the dimmer with a regular switch, as the damage that can
be caused is not worth the risk.

These dimmers use "phase control", they chop the ac waveform based on amplitude
to reduce power, which results in square and pulse waves instead of sine.

>this outlet came to mind after i realized that i need some kind of variac to

>bring up my newly re-capped tube amp.  if i plug the amp into the outlet,
>and turn the dimmer up slowly, is this the same idea as a variac?  
>
>what's wrong with the logic on this one?  it can't be that easy...
>
Variacs are transformers which reduce the actual waveform amplitude without
changing the shape. Neccessary for powering up old tube units to avoid exploding
the power supply filter caps that haven't seen a charge in many years.

Using tube rectifiers does not help as they apply full voltage quite quickly
once they sart to reach temperature. But they do help by not applying voltage
to the tubes until their filaments are warm, which prolongs their life.

Take care,
Doug (NOT an EE)

______________________
The Electronic Peasant

www.electronicpeasant.com