Shopping for a variac

[13hm13]

I'm in the USA, so 110-130V is my mains.

Looking for a good reliable variac. Cost should be under $100 USD.
10-20 amps is okay (max. required is enough power for 200w CRT based tv)

New or used is fine-- even classic/vintage in good shape. Made in China okay if the quality/reliability is decent.
I'd rather it be shipped from within USA due to Coronavirus shipping delays from Asia.
eBay or Amazon are okay. AliExpress -- no!
Suggest some options.
Thx!

[bob91343]

I am not up to date on prices for variacs but my guess is that you need to raise your budget if you are looking for something new.

A 5A unit might be more appropriate.  I can't imagine a tv set drawing more than that unless you go back to the 1940s.

[Electro Detective]

Get a good working one from a local seller via Ebay etc

Avoid those suss shiny red widow makers, unless you're already familiar with variac internals
and game to open one up and give it a good check over and de-rate it under heavy load

fwiw varying AC with a load is something to pay once cry once,
and go cheap on other stuff 

Good luck, hope you score a goodie 

[Electro Fan]

Contact and call the owner to discuss variacs, specs, features, reliability, prices, etc.

https://www.ebay.com/itm/USA-STACO-3PN1010-TUBE-AUDIO-POWER-AMP-AMPLIFIER-HAM-LINEAR-ANTIQUE-RADIO-VARIAC/192271396348?hash=item2cc444adfc:g:tRwAAOSwvD5Z69Ta

[13hm13]

Contact and call the owner to discuss variacs, specs, features, reliability, prices, etc.

https://www.ebay.com/itm/USA-STACO-3PN1010-TUBE-AUDIO-POWER-AMP-AMPLIFIER-HAM-LINEAR-ANTIQUE-RADIO-VARIAC/192271396348?hash=item2cc444adfc:g:tRwAAOSwvD5Z69Ta

Nice ... but US $269.00!!! Didn't you read my OP
I was thinking more ....
https://www.amazon.com/gp/product/B076Y2XHRS/

YaeCCC Auto Voltage Transformer AC Variable Voltage Converter Transformer 110VAC Input, 0-130VAC (500W)

NOTE: It's only 5 amps, but I think this will be fine (my orig. thought was 10-20amps, but that, as I now see, is not needed.

[Ian.M]

That looks fairly cheap & nasty.   The most important thing to know is the load current so you should have an ammeter on your Variac, as overloading one is *BAD* and  usually expensive if you don't react quickly enough to cut power or back off on the knob.   The voltage readout a cheap meter like that gives you is really no better that what you already know from the knob position and your supply voltage, so the meter is essentially worthless.   If you do get one, treat it as a Variac 'kit', open it up and check all the wiring, and ask here if anything seems odd before putting it into service.

[Shock]

Powerstat 136B or 236B

High quality, reversible percentage/voltage face plate, can be horizontal or vertical mounted, in or outside of an enclosure. Seperate voltage taps and can have custom socket enclosure mounted over the connections. You should be able to get replacement brushes for them as well.

Remember with large transformers etc you have inrush current which can trip your mains if you have fast acting circuit breakers. So you may need a soft start solution depending on what you are doing.

[Gyro]

Whatever you buy, make sure you modify it to add a fuse on the OUTPUT.  When the output voltage set low, it's very possible to burn out the winding / wiper contact without getting anywhere near blowing the input fuse or breaker.

[drussell]

Looking for a good reliable variac. Cost should be under $100 USD.

I don't think those two things are compatible. 

If you find a new one for under $100, it will be pretty much complete junk, though it may be sufficient as a starter model for your purposes if operated with care.  A good quality used one, in working condition, will usually set you back more than that also, but you end up with a much more robust, reliable piece of gear that will likely last a lifetime unless it is abused.

YMMV, and good luck. 

[Electro Fan]

Contact and call the owner to discuss variacs, specs, features, reliability, prices, etc.

https://www.ebay.com/itm/USA-STACO-3PN1010-TUBE-AUDIO-POWER-AMP-AMPLIFIER-HAM-LINEAR-ANTIQUE-RADIO-VARIAC/192271396348?hash=item2cc444adfc:g:tRwAAOSwvD5Z69Ta

Nice ... but US $269.00!!! Didn't you read my OP
I was thinking more ....
https://www.amazon.com/gp/product/B076Y2XHRS/

YaeCCC Auto Voltage Transformer AC Variable Voltage Converter Transformer 110VAC Input, 0-130VAC (500W)

NOTE: It's only 5 amps, but I think this will be fine (my orig. thought was 10-20amps, but that, as I now see, is not needed.

I did see your original post with your price target.  I think it’s always good to be careful not to push someone beyond their budget as that is an important personal decision.  At the same time if someone asked for advice on a reliable/safe car and I thought their budget might be half or less of what it might take to get a reliable/safe car I might try to explain why it’s possibly a risk.  But rather than me explain it I thought you might benefit from a phone call with someone who I believe has the expertise to help you see the possibilities.  I bought a variac from the guy who owns the business in the link years ago.  I have run it on a 15 amp circuit with a varying but fairly heavy load for days at a time over the years and so far so good.  No big deal, any good variac should do likewise.  My variac has a meter for current with two sensitivities as well as a voltage meter.  Again, not a big deal.  The reason for the suggestion is that I remember speaking with the owner.  He could cite chapter and verse various General Radio models and the more or less the history of variacs and he offered to build or refurbish almost any type of variac I wanted.

Overall I found him to be willing to discuss variac designs at length but maybe most importantly in my book I found him to be both credible and trustworthy. Plus he was a super nice guy who delivered an excellent product that was exactly as he represented.  I think because he sells so many variacs of many configurations he can probably get the price down as low as anyone for a given level of functionality and reliability but he won’t sell you something unless he believes it’s safe.

Can’t hurt to call.  If his price is too high at least you will have heard whatever he has to say which might help you choose a variac from somewhere else.  Just my thoughts.  It’s your decision, of course.

[Electro Fan]

Fwiw, my variac looks a lot like this plus two meters and two fuses and it looked like it just came new (inside and out) from the factory.

https://www.ebay.com/p/1127332453?iid=372842692756

Call the owner in that eBay link above that I first posted above (I don't know anything about the unit or seller in this link just above in this post).


Edit: Ok, here you go
http://www.shitintogold.com/VARIAC.php
http://www.shitintogold.com/

Another Edit: Owner's name is David.  Looks like he might have a different/new URL; I think the company name was / maybe still is DRCO.  I might have picked a different URL but you're buying a variac not a PR firm.

Yet another edit:
Tell David you don't want (can't afford / can't justify) the brand new cosmetics - you just want his least expensive reliable variac and see what he says.  His pricing reflects the fact that he likes to make products that operate like and look like they came new from GenRad decades ago - but I think he can cut the price down if you go for the electronics over the case condition.  Tell him that you are going to report back to EEVblog if he takes good care of you (that's his only MO anyway) and therefore this is his chance to tap into a new market - but first you need a reliable variac that you can afford.  If his least expensive unit is too expensive for your budget keep shopping elsewhere - but I think he will try to take good care of you.

Good luck!

And another PS,

Those Powerstats like Shock posted look good.  Ask David if you go for a Powerstat vs. a GenRad if that would help keep the budget in line.  For all I know the Powerstats might be the same or more or less; the good thing with David is that he just likes making and refurbing good products and he's big into variacs.  I don't think he has any axe to grind whether it's Powerstat, GenRad, Staco, or any other manufacturer, model, or design.  It's like asking Michelangelo for something in marble - but it needs to be an affordable statue.

[Cubdriver]

Skip the cheap Chinese-made ones and go with old American iron.

Examples:
https://www.ebay.com/itm/Powerstat-S1138-Variac-Variable-Autotransformer-0-140V/162588872075?hash=item25db0d4d8b:g:3ZwAAOSwfIxZZodq
https://www.ebay.com/itm/4211-STACO-3PN1210-Variable-Autotransformer/143152811752?epid=27009075506&hash=item2154928ee8:g:eL8AAOSwfCZZ1pC-
https://www.ebay.com/itm/Superior-Electric-Powerstat-Type-3PN117B-Autotransformer-0-120-V-12-A/133080862801?epid=1781743689&hash=item1efc3cd051:g:XkYAAOSwRjlc~uAH:sc:USPSPriorityFlatRateBox!06795!US!-1

If you're willing to wire in the connections yourself:
https://www.ebay.com/itm/Superior-Electric-Company-Powerstat-Variable-Transformer-Type-116-0-140V-Output/324143800062?hash=item4b7879defe:g:~cYAAOSwvpZeoIjn

This one needs a cover for the connections:
https://www.ebay.com/itm/STACO-ENERGY-1210CT-VARIABLE-POWER-TRANSFORMER/192886776612?epid=8032348549&hash=item2ce8f2a324:g:IKQAAOSwUuNcvkf6

Just some options.  Good luck in your search.

-Pat

[BravoV]

Below is Matsunaga, well known intenational brand variac manufacturer for decades, and I've seen one at industrial site that is still working fine after 50 years. 

Its 1 KVA rated, bought it used, and did inspection tear down when I received it.

Here are few photos of it's internals.




The carbon wiper and exposed windings close up shots ...

[drussell]

Whatever you buy, make sure you modify it to add a fuse on the OUTPUT.  When the output voltage set low, it's very possible to burn out the winding / wiper contact without getting anywhere near blowing the input fuse or breaker.

Indeed.  A proper old-school variac is usually wired this way:



Obviously you could add an input fuse also on a smaller model or a cheap one that you don't trust the autotransformer windings on, but traditionally on larger ones they don't even bother with an input fuse.  That's what the branch circuit supply breaker is for.   

As for the prices, paying $100-150 or even more, for a quality used unit in good shape by the time you have it shipped, etc. is actually a bargain compared to some generic $60 Chinese unit in the long run.

There is a reason why something high-quality like a brand new production 10A  ISE "Variac", a Superior "Powerstat", or a STACO Energy variable autotransformer costs $750. 

[13hm13]

Great tips everyone!

I like the idea of buying a new eBay/Amazon China-made unit and modding it for better safety and reliability. I realize that if the Chinese variac is pretty crappy to begin with (cheap, low -quality coils, etc), modding it for the better may be impossible.
All the "red" China units (eBay or Amazon) seem to ultimately be sourced from a single source. And have generated sizeable and favorable Amazon reviews (for what those are worth).

[tkamiya]

Contact and call the owner to discuss variacs, specs, features, reliability, prices, etc.

https://www.ebay.com/itm/USA-STACO-3PN1010-TUBE-AUDIO-POWER-AMP-AMPLIFIER-HAM-LINEAR-ANTIQUE-RADIO-VARIAC/192271396348?hash=item2cc444adfc:g:tRwAAOSwvD5Z69Ta

Nice ... but US $269.00!!! Didn't you read my OP
I was thinking more ....
https://www.amazon.com/gp/product/B076Y2XHRS/

YaeCCC Auto Voltage Transformer AC Variable Voltage Converter Transformer 110VAC Input, 0-130VAC (500W)

NOTE: It's only 5 amps, but I think this will be fine (my orig. thought was 10-20amps, but that, as I now see, is not needed.

I have that exact same one, purchased from Amazon.

It's rated for 0.5KVA but based on size, weight, what I had in the past, and general knowledge in transformers, I wouldn't rate it at that.  Honestly, 2A maybe more reasonable limit.  The meter and the dial is way off, so be sure to have a DVM and check it before plugging anything in.  On spec, they mix up amps, watts, and VA.  They are very confusing and not to be trusted.  I also don't feel comfortable using it unattended. 

If I have to do this again, I'd buy a used one, either Japanese or American made.  You'd be surprised how big and heavy they are for given amperage. 

[drussell]

All the "red" China units (eBay or Amazon) seem to ultimately be sourced from a single source. And have generated sizeable and favorable Amazon reviews (for what those are worth).

They're not all red.

My local industrial electronics shop stocks everything from the $700 STACO to some cheap Chinese one that is only a slightly-more-robust version, painted beige instead of red, that came out of the same Chinese factory of your above-linked Amazon listing.

They also don't always get great reviews....

Unit received inoperative. It did not show any voltage on meter although power switch lit when unit turned on. Checked fuse and found it to be good. However, noticed that upon screwing fuse holder cover back onto fuse holder there was no back pressure to indicate that the fuse was seating properly. Removed two front screws, examined interior and found that fuse holder was broken. Having several spare fuse holders of this general type, replaced holder and soldered two wires back into place.

Horrible wiring. The solder joints in this device are terrible and the input live broke off the switch after about a month of use. Unaware of the loose wire, I plugged it in yesterday and was greeted with sparks and a pop. Thankfully the gfci outlet did its job. The pictures I included show where the short occured as well as the haphazard wiring my device was shipped with.

Also, the indicated voltage on both the reference dial and analog v-meter display voltages substantially below what the true output is. I can't remember the exact numbers but I was measuring something like 135V output when the device was set to 110V.

As other reviewers have mentioned, do not buy this device without a strong working electrical knowledge. This tool needs to be checked before use (which I failed to do) because there are obviously QC issues.

After taking the time to rewire everything with the appropriate terminals and resoldering, the problem with mine is fixed. However, because of the unsafe condition this was out of the box I reccomend spending the extra money on a safer, higher quality unit.

YMMV. 

[tkamiya]

Now, I have a sudden urge to do some destructive testing.  500 watts worth of incandescent light bulb as loads, instrument it and let it run.  (outside on concrete)

[drussell]

Now, I have a sudden urge to do some destructive testing.  500 watts worth of incandescent light bulb as loads, instrument it and let it run.  (outside on concrete)

Run it down from the top if you do, it will likely blow up at the bottom, probably even if you used an active constant current load instead of bulbs or heaters which will slowly become lower and lower resistance at lower and lower temperatures. 

Those little junk units aren't even rated for their actual load current and why they would specify a VA rating when you can't even get like 50 VA out at the bottom of the winding without ending up with what amounts to more of arc welding of the windings, I don't know... 

Take a look at something like the STACO brochure and you'll see that they rate them to do the full current even at the low end.

I doubt those Chinese units will fare so well above, like you say, perhaps 250VA?

And what about a rectifier-capacitor load?  With those tiny autotransformer windings?  Current peaks?!  No way.

Please post video. 

[Cubdriver]

Great tips everyone!

I like the idea of buying a new eBay/Amazon China-made unit and modding it for better safety and reliability. I realize that if the Chinese variac is pretty crappy to begin with (cheap, low -quality coils, etc), modding it for the better may be impossible.
All the "red" China units (eBay or Amazon) seem to ultimately be sourced from a single source. And have generated sizeable and favorable Amazon reviews (for what those are worth).

You are correct that a basic variac doesn't consist of much beyond the coils and brush.  Given that, if the heart of the device is crap, what do you expect to modify to make better?  I'll repeat my suggestion that you go with a used version of a major US or Japanese brand - they are well built, conservatively spec'd and very reliable if not horribly abused.  We got one of the red ones at work - needed to buy 'new' for a small project.  It's a hunk of junk - I much prefer my 30+ year old Superior Electric models.  I got one of them surplus when NSC closed their Danbury CT plant 30 years ago.  It was old then, and had been in service powering an adjustable heater in the dopant supply section of a diffusion furnace for probably 15-20 years at that point.  It's not pretty, but it works perfectly.

Buy once, cry once.

-Pat

[engrguy42]

Now, I have a sudden urge to do some destructive testing.  500 watts worth of incandescent light bulb as loads, instrument it and let it run.  (outside on concrete)

Now you're talkin'.  Nothing like actual data rather than vague generalizations.

I'm all for the "don't buy junk" motto, but I'm also mindful that in the tech world there's a whole lot of paranoia over stuff people maybe heard about something and made up their minds, but never actually tested it themselves. Y'know, like, say, ATX power supplies. 

Anyway, I'm also kinda wary of buying stuff on eBay that's obviously been used for decades. Yeah, that US-made stuff was probably built extremely well, but who the hell knows who used it, and on what?

As far as variacs, I'm also considering buying one maybe. And I'm trying to figure what actually can go wrong with them that make them "junk". Hell, it's a variable autotransformer. Is the wire insufficient to handle the current? The insulation insufficient? The only moving part is the brushes, so are they gonna fail? Maybe they get damaged in shipment since it's such a big heavy thing? Of course the built-in meter is probably inaccurate as hell, but that's why we have multimeters. And fuses are cheap.

I dunno, I'm a bit skeptical about the skepticism... 

[drussell]

And I'm trying to figure what actually can go wrong with them that make them "junk". Hell, it's a variable autotransformer. Is the wire insufficient to handle the current? The insulation insufficient? The only moving part is the brushes, so are they gonna fail?

Well, yes, it is just a variable autotransformer, so the windings could be burned, broken, shorted, etc.  Sometimes that can be mitigated by bypassing a couple of turns by removing and then shorting the wiper-contact-area of those turns so it just has an "uneven" spot instead of a total dead spot or open winding, or whatever...

Brushes?  Yes, the brush contact assembly can require careful refurbishment or outright replacement if they have been used heavily or overloaded repeatedly.  They are typically still available for even older models but expect to pay close to $100 for the complete replacement brush and holder assembly, though if not abused a new one should easily last another 50+ years in regular operation.

[engrguy42]

And I'm trying to figure what actually can go wrong with them that make them "junk". Hell, it's a variable autotransformer. Is the wire insufficient to handle the current? The insulation insufficient? The only moving part is the brushes, so are they gonna fail?

Well, yes, it is just a variable autotransformer, so the windings could be burned, broken, shorted, etc.  Sometimes that can be mitigated by bypassing a couple of turns by removing and then shorting the wiper-contact-area of those turns so it just has an "uneven" spot instead of a total dead spot or open winding, or whatever...

Brushes?  Yes, the brush contact assembly can require careful refurbishment or outright replacement if they have been used heavily or overloaded repeatedly.  They are typically still available for even older models but expect to pay close to $100 for the complete replacement brush and holder assembly, though if not abused a new one should easily last another 50+ years in regular operation.

Yeah, but what, specifically, about those cheap Chinese "junk" variacs is junk?

[tkamiya]

What specifically make it a junk?

It's too light.  That means the core (that wires are wound on) is too small.  It will saturate and overheat.  Wires are also too thin for the rating.  When I lived in Japan, I had a 250VA version.  It was larger and heavier than this thing.

My prediction is, it will get way too warm, possible smoke, possible broken wire, but I don't expect anything spectacular.  I think I have a 500 watt light bulb somewhere, so I'll use that as a load.  Thermo-couples on bottom, face plate, sides.  Clamp on meter for current at input, Voltage at the output.  Run it for one hour at half way point, and another one hour at whatever the bulb is rated.  (120V?)  Then rotate the slider from 0 to 120V back and forth few times.  This is when I expect something to go wrong. 

Breaking it isn't the point, and stressing until it melts isn't a point either.  My goal is to determine, if _I_ feel safe using this at the rating.  Obviously, at half way point, it won't be expending 500VA.  I am a licensed electrician but this is only a partial and personal test in home setting.  I don't endorse, approve, or guarantee anything and if anyone decides to buy it, they do so at their free will.

It might take me few days but I've been wanting to do this for a while, so I will do it.  Just don't stay up all night waiting for it. 

[Electro Fan]

And I'm trying to figure what actually can go wrong with them that make them "junk". Hell, it's a variable autotransformer. Is the wire insufficient to handle the current? The insulation insufficient? The only moving part is the brushes, so are they gonna fail?

Well, yes, it is just a variable autotransformer, so the windings could be burned, broken, shorted, etc.  Sometimes that can be mitigated by bypassing a couple of turns by removing and then shorting the wiper-contact-area of those turns so it just has an "uneven" spot instead of a total dead spot or open winding, or whatever...

Brushes?  Yes, the brush contact assembly can require careful refurbishment or outright replacement if they have been used heavily or overloaded repeatedly.  They are typically still available for even older models but expect to pay close to $100 for the complete replacement brush and holder assembly, though if not abused a new one should easily last another 50+ years in regular operation.

Yeah, but what, specifically, about those cheap Chinese "junk" variacs is junk?

Lots of people here know more about this than me but it's my understanding that, among other things, in a well made variac tolerances are tight (thousandth of an inch or better, better than you can usually get with a hand file), the compositions and  plated materials are made to avoid wear and corrosion, and generally the old school brushes were not dependent on (ie had no) heat sinks.