Building a variac

bereanbill · 12th April 2009, 06:55 PM

Hi again..anyone have plans for building a variac ? How hard can it be ?

Brett · 12th April 2009, 07:03 PM

Why would you bother? They're cheap enough second hand.

bereanbill · 12th April 2009, 07:42 PM

I guess just for the sake of accomplishment...

zman3 · 14th April 2009, 05:42 PM

I'll have to agree with Brett; there are many other things you can do in this hobby that would fill you with a greater sense of accomplishment for far less money and/or aggravation (custom winding an output transformer or building a line-level preamp both spring to mind).

Just in case nobody has mentioned it, try to attend a local hamfest. I've picked up 10 A variacs fused and in housings for as little as $5 - and I can assure you they're FAR safer and more reliable than anything you can build.

Robert McLean · 14th April 2009, 11:43 PM

Here is a possible compromise answer :
Buy one of the cheap readily available variacs, you will have a good safe one, as Brett and Zman3 suggest,
then
copy it, and your desire for a sense of accomplishment will be satisfied.

Brett · 14th April 2009, 11:59 PM

I didn't mean to rain on anyone's parade, but for the same effort you could wind your own audio transformers which will teach you more and you'll get a lot more use out of. I use my variac a bit, and on a busy week it'd be lucky to get an hours use.

bereanbill · 15th April 2009, 12:13 AM

Thanks for the input. Winding trannies is on my accomplishment list, but I don't think I'm quite ready for it yet...baby steps first. I'm kind of a Rube Goldberg-type, so anything is gratifying to me. With the clunkers I have around, a variac will get quite a workout in my laboratory.

Brett · 15th April 2009, 12:21 AM

Some reading for you then.
Turner Audio Educational pages

There's quite a bit on load matching, as well as OPT design info a bit further down.

Iain McNeill · 15th April 2009, 12:22 AM

I have to reinforce the sentiment here...

A variac is an instrument of death (anything that connects directly to the mains is lethal) This isn't a good choice for a 1st build.

Buy a good safe one and it will help protect you during your other experiments

TubeMack · 15th April 2009, 12:49 AM

Any recomendations? I just picked up one as a part of a test equipment buy. It looks to be from the 30's,and the cord appears to have caught fire!

I'm guessing I shoud just junk it. I'd like something newish and cheap.

12th April 2009, 06:55 PM	#1
bereanbill diyAudio Member Join Date: Jan 2009	building a variac Hi again..anyone have plans for building a variac ? How hard can it be ?

14th April 2009, 11:43 PM	#5
Robert McLean diyAudio Member Join Date: May 2005 Location: Stittsville, Ontario, Canada	Here is a possible compromise answer : Buy one of the cheap readily available variacs, you will have a good safe one, as Brett and Zman3 suggest, then copy it, and your desire for a sense of accomplishment will be satisfied. __________________ Robert McLean

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12th April 2009, 07:03 PM	#2
Brett diyAudio Member Join Date: Jan 2002	Why would you bother? They're cheap enough second hand.

12th April 2009, 07:42 PM	#3
bereanbill diyAudio Member Join Date: Jan 2009	I guess just for the sake of accomplishment...

14th April 2009, 05:42 PM	#4
zman3 diyAudio Member Join Date: Feb 2008	I'll have to agree with Brett; there are many other things you can do in this hobby that would fill you with a greater sense of accomplishment for far less money and/or aggravation (custom winding an output transformer or building a line-level preamp both spring to mind). Just in case nobody has mentioned it, try to attend a local hamfest. I've picked up 10 A variacs fused and in housings for as little as $5 - and I can assure you they're FAR safer and more reliable than anything you can build.

14th April 2009, 11:59 PM	#6
Brett diyAudio Member Join Date: Jan 2002	I didn't mean to rain on anyone's parade, but for the same effort you could wind your own audio transformers which will teach you more and you'll get a lot more use out of. I use my variac a bit, and on a busy week it'd be lucky to get an hours use.

15th April 2009, 12:13 AM	#7
bereanbill diyAudio Member Join Date: Jan 2009	Thanks for the input. Winding trannies is on my accomplishment list, but I don't think I'm quite ready for it yet...baby steps first. I'm kind of a Rube Goldberg-type, so anything is gratifying to me. With the clunkers I have around, a variac will get quite a workout in my laboratory.

15th April 2009, 12:21 AM	#8
Brett diyAudio Member Join Date: Jan 2002	Some reading for you then. Turner Audio Educational pages There's quite a bit on load matching, as well as OPT design info a bit further down.

15th April 2009, 12:22 AM	#9
Iain McNeill diyAudio Moderator Join Date: Oct 2007 Location: Santa Cruz, California	I have to reinforce the sentiment here... A variac is an instrument of death (anything that connects directly to the mains is lethal) This isn't a good choice for a 1st build. Buy a good safe one and it will help protect you during your other experiments

15th April 2009, 12:49 AM	#10
TubeMack diyAudio Member Join Date: Apr 2006 Location: Florida	Any recomendations? I just picked up one as a part of a test equipment buy. It looks to be from the 30's,and the cord appears to have caught fire! I'm guessing I shoud just junk it. I'd like something newish and cheap.

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