When powering any old tech for the first time in decades, it's best to use a variac to turn up the voltage slowly and monitor the input power to make sure there are not any shorts and to prevent "magic smoke" from coming out of the device.
I have the same variac but in the 30 amp version. I'm pretty happy with it. It has wire nut terminals instead of the plugs, two handles on top, and is a bit larger. For the price ($120) plus like $12 shipping it's really quite nice, I've seen name brand variacs that are comparable go for more than double the price. Mine has 2 brushes as well, and the windings look just like yours. They have no problem carrying the current. They had no provision for a ground so I ground a bit of paint off where a screw goes and ran my ground there. Also on the accuracy of the dial, it does depend on the input voltage greatly. On the front mine says 110v. My mains is 120v so it's not accurate. My overwind also goes to about 145v which is pretty nice. I made up a little information panel with a secondary side fuse, larger analog voltmeter, and ammeter to make it easier to use. Also added was a bridge rectifier, which makes it a pretty nice power supply. All I'm missing are a few ballasts.
InductiveExperiments Wow, that sounds great. I'm ok with the scale being dependent on the line input voltage but was not so happy with it not being linear. I like your modes, any changes you can share photos, diagrams and a bom listing?
***** I do have a few videos on it with "information panel" in the title. It's kind of stuck in the prototype phase since I'm okay with how it is now but it's not very sturdy. I'll put it all in a box eventually which will just make it easier to move around. And maybe make a switching device to go from ac to dc instantly and not have to change the terminals. The variac itself only has one change, that's the grounded frame. I show both in the videos. It's a pretty cool setup though, just not as good as what youtube user "photonvids" did in his video called "Easy Electrical Project" I like that one.
Hiya. Nice little review on this. A few things about it though which I'd be unsure about: (1) That earthing/grounding.... I have my doubts that would pass UK safety standards. As a qualified Portable Appliance Tester (PAT), I'd be kinda inclined to fail that on the basis that there isn't a dedicated earth connection to the chassis. Relying on mechanical fixings to carry-on the earthing continuity like that is a bit naughty. With the way that socket was flapping around in there, I don't think it's going to be too long before that screw loosens-off, and the split second it does..... No earthing to that chassis. NAUGHTY! :-O I'd be straight in there to make a dedicated earthing connection from that earth wire, to the little removeable casing/terminal cover, and the base of the chassis onto which the outer casing is connected. (2) What's all that hot glue around that power cord in there? Subjecting that cord to that kind of thing could've damaged the insulation inside the power cord. Let's hope they tested the cord's integrity before it left the factory. (3) Fuse. That would be better on the output than the input. From what I have heard, if the fuse is on the input side, it can be perfectly possible for that fuse while under load to be only seeing 3 or 4 amps, but the output could be pulling a good 25A through the brush, (especially if the test subject faults-out or goes hard-short) and that's when you start blowing windings and popping brushes. I'd re-configure the wiring in there so that the fuse is on the output side. Better still, have two fuses: One on the input wire and one on the output wire. The bets are on that, should you ever accidentally overload that variac, it'll be the output fuse which pops first. :-) (4) Output voltage. Obviously speaking, what you get out of the variac does depend on what is going into it to start with. If I was going to "re-calibrate" the dial on top of the variac, I'd want to calibrate the input voltage first, as you obviously can't re-position the input wire to the windings in there to pull things into line. If your input voltage is supposed to be say, 120v and you're getting 122v or 118v, that will affect your output. Calibrating the input voltage could be done with another variac, by turning the first one upto a certain voltage, of which is measured by a calibrated volt-meter, then once you're happy with the input voltage to the second variac, then start working on "re-calibrating" the voltage plate on top. I'd keep the volt-meter on the output of the first variac, just in case a regional voltage variation occurs during the recalibration of the second variac. That way, if the regional voltage does drop off a couple of volts or increase by a few, you can 'pull-in' the calibration voltage merely by tweaking the dial on the first variac so that the volt meter reads your desired calibration voltage once again. While I understand that everyone doesn't have the luxury of owning two variacs, it does help if you really want to go into very precise voltage calibration. Then, once you have 're-calibrated' the voltage plate of the second variac, don't forget to write on it somewhere what the calibration voltage was. :-) ------------------------------------ Overall though, it's a cute little device. I wouldn't rely too much on that built-in volt meter though. :D -BoomBoxDeluxe.
Thanks for the review. I've got variacs all over at home and at the lab. I use them for soldering irons, as you said, plus Tesla coil, incandescent light bulbs, window fan, home made variable power supply, and countless other applications and experiments. Just used one yesterday to test a FWBR.
Hi, just to add regarding the voltage not equal to the dial. In most cases you will find it will only be equal when the input voltage is correct to the system! ( eg. System equals 120v and calibrated @ this voltage from factory) So if the input is not 120v the dial will be out to the output!
The inaccuracy is probably because of variations on the mains. Don't know about the US but +/-10% is allowed here, I think. Always a joy to see your vids :D
The scale on the Variac dial is % of input voltage, not absolute voltage. Your input voltage is 115V AC (or whatever) not exactly 100. That explains the offset you're seeing and why your own meter agrees with the built-in one.
Hi, I acquired my variac pretty much in the same period as you did you clip, however this is the first time I see your video about the variac on UA-cam. I did modify the wiring so that the fuse is actually protecting the variac's output. Afterall, the variac's input is protected via the circuit breaker on which it is connected. If someone really wants to make it safier, a fuse on the input and one on the output is an alternative to consider too. As you stated, and also reported by other buyers, the ground connection wasn't adequate. This is one of the first thing I checked when I acquired the variac and fixed it ASAP ! I would appreciate if someone could tell me if they experienced breaker trippings because of the inrush current when they turn on the variac ? Even if the dial is at the lower setting, no load, the breaker trips when I turn on the device. This is fairly annoying. Some hobbyists are using the light bulb trick to minimize the breaker tripping, but personaly I'd rather prefer a more genuine soft-start approach. Would you have any suggestion in that regard ? Finally, I ordered a small panel voltmeter that I will make fit in place of the analog meter. There is someone on UA-cam who did that modification, however it works in a similar way as your Watt meter, showing the reading around 40V and up. On my end I opted for a meter requiring an external source to operated, therefore I'll be able to see the reading in the lower ranges. Keep up with the good work !
Great video! Thanks for this. I can see I should open mine up and look at all the things you mentioned looking out for. $99 for 20 amps is a great deal. Mine is fused at 3 amps and I think it cost me around $70 new. I use mine to feed my 24VDC power supply, so I can vary its output between 0-24VDC. Then I can plug my 30kV DC high voltage power supply into my 24VDC power supply, so I can vary that too.
Good review thank you. I wondered why there was no CE, CSA or other symbol to verify it passed. This one would surely fail, just on the ground connection by itself. It looks pretty good otherwise, I wonder why they didn't bother with a simple screw and wire to the chassis to attempt to get certification. For a lab device the calibration of the meter isn't important, most of us would measure that directly with a scope or MM anyway.
Wish you would have shown the bottom of the unit so we can see how well the shaft is supported without a bearing like most other Variac's. The one I had there was problems with the knob having side to side play allowing the unit to lose connection between the brushes and the top of the transformer coil, even allowing some small sparks inside the unit.
I have an old adjust a volt standard electric variac. It will do 0-140V AC up to 7.5 amp. When I got it it had an really old 2 prong un-polarized plug. I redid that with a 16AWG 3C cord from an old microwave, then just took a 3 prong adaptor and bonded the ground to the metal frame. I then got a 7.5 A breaker to replace the fuse holder. I fin interesting at one time I thought variacs were just some wacky part with not much use. I use it like all the time now though, I really like I can use it to test transformers. If I put 2V in and get 10V out then I know the ratio. One time I needed 480V for a project I connected an old microwave transformer to the variac then turned it up to like 20V and that gave me 480 V from the MOT. The other day I used it I had had to test a transformer with a 208V primary. I had another one that had a 120 primary and 208 output. I took the 120 input connected to the variac for adjustment reasons, then wired the output 208V to the input 208V of the transformer I wanted to test. I also have an accessory I made that has a lone cord for the variac on it then that connects to a bridge rectifier heatsank to the metal box. The output then attaches to a filter cap and terminals. The other thing I use with it is an old 18AWG 3C cord with 3 insulated aligator clips on the end. Then I can clip to transformer leads, motors, etc and run them on the variac. Last week I got 4 variacs that came from a control panel setup. They were rated for 3A at 280V. I wanted to find if I could use a different setup to input 120V and get the proper range still. I used the variac I had and my test lead to test various connection points on my new variac to find the best connection for a 120 input. In a way I find that funny because I used one variac to test a different variac. I also used to drive an old ignition transformer from an oil furnace to make a jacobs ladder. It I had the gap a bit too big I could boost it to 140V, or bring it online slowly to see what happens. Thay can also be used with AC to control amperage because it is basically a variable inductor. My next project is to take 2 of the 4 variacs I got install them in a metal toolbox, use one for voltage adjustment and the second for amperage control. I may put a few switches in too to adjust the primary windings on the voltage variac, and maybe another to bypass the amperage control variac. The outputs would be AC, then also have a DC output with a rectifier and filter cap(s). Perhaps at some point I may think about adding a regulated output too. These variacs are only rated 3 amp, but from what I have heard many places if you cool them fairly well you can overload them a good deal. unless it gets to be like 10+minutes, etc.
I know this is an old video but I wanted to comment for possible future viewers. I have an one Adjust-A-Volt as well. Mine is a 15 amp version. I’m pretty sure that the dial is marked in percentage of the total output voltage, and not in actual voltage. That’s why it never matches up. If I remember correctly, when I tested mine , by percentage it was in the ballpark. +/- 5% I believe.
Thanks for the info, I recently found a powerstat 246 variable transformer while cleaning out a barn, unused still in the box. I had no idea what i was looking at, now I just need to figure how much it is worth.
Nice review. My thoughts:- * If the wires were spade connected, some clown would probably re-install them arse-about. * Can you could lock the knob properly onto the shaft flat, and then fix the zero offset using the set screws on the wiper collar. * I would install proper ground wires to all 3 chassis parts, also putting some extra length on the wiring inside the power cover. * Maybe some hot snot would stop the output sockets flapping about.
@Eric William, Thanks. True, 210mA seems low but it was a Harbor Freight item so maybe its broken. I ran my 5Hp air compressor at ~14A for 10 minutes on the variac and the variac didn't even get warm. Nice.
Hi Todd, wanted to ask you a question about using a variac to lower the voltage of a 100 watt Marshall guitar amplifier. How many amps rating would you need, 10A or 5A at 500 watts like the SC-5M model sold from China that looks like the one you have? My amp uses a 4amp fuse. My other 50 watt amps use a 3 watt fuse.Hi Most people say you should buy an old Staco variac made in the USA. how do you find the quality of these Chinese variacs? I would appreciate your expertise on which variac I should buy. I searched all over UA-cam and the net and still haven't found the answer to my question. Thanks Michael Newell from Niagara Falls, Ontario, Canada
Find the rating of the input to your amplifier (usage rating from mains). If that is only 100 watt or less then the 5A china variac will work just fine. Just make sure the amplifier input is less than the rating for the variac and the china variacs are fine.
Todd I bought a variac and am having some issues. I’m outside my return window so I’m going to have to deal with it. Can I email you some pics of what I’m working with? Thanks in advance.
That 110V variac would work on 240v mains, wouldn't it? Only the scale on the dial would be wrong and the little volt meter would go "pop". Or would the variac windings get hot and melt? If not, is the only difference between a 110V and 240V variac the label on the dial and the little voltmeter?
I think that for every given position of the dial the output voltage will vary depending on what load you connect. The bigger the load (lower impedance) the lower the output voltage will be. Just a reminder. Great video BTW, keep up the good content. EDIT: I just realized after this vid that autotransformers are just variable inductive voltage dividers. en.wikipedia.org/wiki/Voltage_divider#Inductive_divider
I assume you meant "compared to no load" instead of no variac. Interesting that it doesn't vary too much with a load. Good job testing it to make sure! that's not a serious difference in voltage and I probably wouldn't mess with it either.
+MonkeyMagic Elecifun I have done a tear down but not on video. It doesn't have as many features as say a the "RIGOL DP832" (astore.amazon.com/tod0f5-20/detail/B00ENX02GC) but the "CSI3005X" (www.circuitspecialists.com/bench-power-supply-csi3005xiii.html) is still very usable and I have had no troubles with it in all the years I've owned this unit.
***** I had one but killed it within a couple of weeks. It would be great to see a tear down of it. Circuit Specialists over here (UK) asked me pull mine apart to find the fault. I did and did, but I didn't like the lack of features, Output button,resolution, current control to name a few. I bought the Rigol DP832 and have never looked back. PS I think your Auto Transformer review, tear down is great, I am looking for a not too expensive unit and think I may have found it. Cheers.
I plugged a receptacle ground tester into mine and under 60v it's says the ground is fine but anything higher it says it has a bad ground. I even scratched of the powder coat off around the ground lug & it still does it, any idea why?
This is an auto transformer and your receptacle tester needs to measure the ground leg through the neutral leg. Maybe your neutral and hot are switched in your wall receptacle or in the variac plug or in the variac wiring or at the service panel. I thing this would cause your problem as it may not like the value it gets through the windings of the variac if the neutral is on the hot side going into the variac windings. That said, your tester shouldn't even be able to power on until after the variac gets over 60v AC as that is what it takes to turn on the 110 V Neon Indicator Lamps normally found in such receptacle tester plugins, this makes me think you have some bad wiring. I tested my variac with my 110 V Neon Indicator Lamp receptacle tester and it stayed off until 65 V AC then turned on with one light stating bad ground, then at about 80 V AC to max AC voltage it showed two lights indicating all good. Hope that hepls
I didn't like those crappy ground connections either. And I think "common" applies more to DC circuits. I think "neutral" is best for AC. Your review was good, very thorough, almost Dave Jones-y. Include a ToddCAD schematic and it would be perfect as a variac introductory tutorial. I learned a few things from the historical perspective. Glad you like my videos! Have some plans to do a few more JT experiments using optoelectronics. What's up with that CCFT power supply in the background?
Great video! I have the SC-10T which is rated for 10A and is isolated, but the front panel is identical. I'm planning on modifying it to add a digital display with an ammeter and volt meter. Did you notice that if you pull the fuse, the light on the switch stays lit. They have the fuse after the switch (between the switch and transformer). Doesn't make much sense to me.
+Todd Harrison (ToddFun) I just lucked upon it while looking for an isolation transformer. Since it was fully isolated, and I'd wanted a variac anyway, I went for it. When my parts get here and I get my modifications done, I'll post a link to pics.
+Todd Harrison (ToddFun) Hi Todd, I went to the store link above and it says "Note - The grounding pass through and bypasses the isolation, which means the grounding isn't isolated. You may be able to use a 3 prong to 2 prong grounding converter." Does that not mean that it is not isolated? If it is, then you should not have to use a 3 to 2 prong converter. Did you have a chance to measure the output wires to ground? Also, could you help explain how they managed to isolate it with only one coil instead of 2 coils i.e. a primary and secondary as in a transformer? Thanks.
+istoreit Thanks for the information. They have changed the product that this links to so I have removed it from my store listing. The one it was linking to was not isolated. I did leave other isolation transformers on my Amazon store that are not variacs. You can get a good Variac and plug it into an isolation transformer to get the same combo.
Hi Todd, Thanks for the review of the variac. I was on the market for one and found your review and helped me pick the same one you have. On bit of good news - the company must have reviewed your comments and added a earth ground wire to the cage! I took mine apart to check the quality and when I took off the front panel, they had already added the extra Earth connection over to the cage (I did add a star washer to make sure there was a good electric path through the paint). Thanks again for the review and take care, h
your voltage at your house will vary seasonally making your top outside scale wrong season to season, building to building, electric supplier to supplier. metering is a must. Also, check the outlet your using for proper ground connection with a test plug before using.
Great video. Mine never worked right. I used your video to clean the coils, remove the armature, adjust the tension rings, reset the armature and reassemble. It works much better now
Another awesome video sir, I recently acquired 2 Superior Electric Co 3PN116B Powerstat Variable Autotransformers off ebay for 5 bucks a pice! Score ob my part, just need to replace old dry rotted cords. I did have a question for you about the scale on these units. The two i have go from 0 to 100 marked, but output 0 to 140 volts, as well as all of the pictures i have seen show a scale of 0-140 volts on them. Is there something odd about the ones i have, or else i have no clue! I took the covers off to check the windings, and the screws appeared to be the original ones. Any guess as to why the output would be labeled this way as to the others i have seen?..
Ray M I don't know why the label is 0-100 unless it is just for a % of output. 0% to 100%. I have seen them with 0-100 but they where the 240v model. maybe somebody just modified a 240v unit to 110v. You could etch your own from some copper plate or make one by hand. Also try to see if the plate flips over, maybe the back side has 0-140v ?
***** I am not even sure how to tell if it is a 240 volt model or the 120 volt one, other than the model numbers. I will try and attach a few pics of the two, but also the rivits in the caps of these original scales appear to be the original ones.
I think I would have sent it back or claimed shipping damages. My AT's fuse completely destroyed itself for no apparent reason so I bypassed it for now, but I really need to put a new "better" fuse holder on it.
Yeah, well, its a cosmetic issue I suppose, I could take it apart and straighten out the metal a little bit better. The problem I believe was that it was too heavy for the thin foam on the bottom, and that is what happened, that it got thrown around and it slightly buckled on one edge, that is what bent in the metal on the round shape. Hey, I tried to avoid this bs,...I noticed the seller was supposedly in California, and I am in Oregon, then when it was shipping it comes from Kentucky,...I messaged the ebay seller, who seemed like a chinese foreigner about this and received a strange foreign like english apology. I paid $76 + $15 shipping, and I alerted the seller what happened, haven't heard back though, and sending it back for an exchange just seems a waste of time, and they are now out of these. Now I have a chinese 30 v 10 amp dc power supply coming from a different seller,....in supposedly chino california, another one of our chinese sellers on ebay, I hope it comes in straight. *****Just got an email from the seller, wanting some pictures of the damage, which I gave, maybe I might get a partial refund, but most likely, in the past from other ebay sellers on partial refunds on chinese made consumer goods, I get a five or ten dollar partial refund while they claim a total insurance payout from the shipper,....I have seen that twice. BUT, the point here is, .....I'd expect the heavy 20 amp variac to be twice as likely damaged or bent up in shipping cause the thin foam on the bottom of the box is too thin and pancakes out in no time allowing the heavy item to be slammed on concrete and other hard surfaces with little protection other than pancaked bottom foam and thin cardboard. Like I said, I have a el cheapo 30v 10 amp dc power supply coming, supposedly from Chino California to southern Oregon(here) from a different seller, and if that comes in all squashed or bent up,....haha, I might need some electro shock treatment so to speak.
What they told me in school was that you can never rely on the scale on top of the variac. The input voltage may vary and when the input voltage is not exactly right, then neither is the output voltage. For an accurate voltage reading, use your own volt meter and ignore the scale. I think the grounding is a big fail! And I don't think your fix is good enough either; the mains ground should be securely connected to ground lugs mounted on unpainted areas of the panel and the main enclosure.
Hi I got mine today, a vevor with digital readout. A 3kva 240 volt. But the output is enormous! 338 volt 😃😁 With shipping to DK only 99$.. These things has becoming really cheap. About using it as a transformer, just remember: It has live mains, there is NO isolation, so one's power supply is LIVE on the low voltage side....
safe ur rahman Thanks. I learn a lot when I make these video too. I want to get everything as correct as possible so it motivates me to learn more making the videos than I would have otherwise known about the product.
Prolly it'd be fine, ofc without the volt meter. You'd have to interpret the scale as a percentage scale. Btw for the same power output in a 230v line you require half the amps you'd need in a 110v so you wouldn't need to bother about the fuse either.
I believe you have hit the nail on the head here. The scale is a percentage scale. If the scale shows 100 at the 1:1 point (110 VAC in 110 VAC out) surely that's the case. Being a percentage scale means that it 'works' irrespective of the input voltage.
Liked the video but there is a lot of info that is redundant. I liked it don't get me wrong but you need to do some editing. Other that that I walked away from this with a good understanding of the unit. P.S fly paper or bug zapper will take care of that fly.
I Like your presentation, Thank you for telling us what is a VARIAC . Great video. PSS, didn't know you are in Az.. Hello Neighbor, I'm here in Surprise Az.
Your initial explanation of an AUTO TRANSFORMER IS TERRIBLE. Take some advice, Soend some time planning what you will say BEFORE STARTING YOUR PRESENTATION
@@ToddFun The presentation appears to be an off hand unplanned performance. As I stated in my first comment there appeared to have been done without ANY FORETHOUGHT.
@@ToddFun It's always worth a chuckle to see people give instructional advice when they don't post videos themselves. Lots of armchair experts who don't understand how difficult it can be.
When powering any old tech for the first time in decades, it's best to use a variac to turn up the voltage slowly and monitor the input power to make sure there are not any shorts and to prevent "magic smoke" from coming out of the device.
I have the same variac but in the 30 amp version. I'm pretty happy with it. It has wire nut terminals instead of the plugs, two handles on top, and is a bit larger. For the price ($120) plus like $12 shipping it's really quite nice, I've seen name brand variacs that are comparable go for more than double the price. Mine has 2 brushes as well, and the windings look just like yours. They have no problem carrying the current.
They had no provision for a ground so I ground a bit of paint off where a screw goes and ran my ground there.
Also on the accuracy of the dial, it does depend on the input voltage greatly. On the front mine says 110v. My mains is 120v so it's not accurate. My overwind also goes to about 145v which is pretty nice. I made up a little information panel with a secondary side fuse, larger analog voltmeter, and ammeter to make it easier to use. Also added was a bridge rectifier, which makes it a pretty nice power supply. All I'm missing are a few ballasts.
InductiveExperiments Wow, that sounds great. I'm ok with the scale being dependent on the line input voltage but was not so happy with it not being linear.
I like your modes, any changes you can share photos, diagrams and a bom listing?
*****
I do have a few videos on it with "information panel" in the title. It's kind of stuck in the prototype phase since I'm okay with how it is now but it's not very sturdy. I'll put it all in a box eventually which will just make it easier to move around. And maybe make a switching device to go from ac to dc instantly and not have to change the terminals.
The variac itself only has one change, that's the grounded frame. I show both in the videos. It's a pretty cool setup though, just not as good as what youtube user "photonvids" did in his video called "Easy Electrical Project" I like that one.
Hiya. Nice little review on this. A few things about it though which I'd be unsure about:
(1) That earthing/grounding.... I have my doubts that would pass UK safety standards. As a qualified Portable Appliance Tester (PAT), I'd be kinda inclined to fail that on the basis that there isn't a dedicated earth connection to the chassis. Relying on mechanical fixings to carry-on the earthing continuity like that is a bit naughty. With the way that socket was flapping around in there, I don't think it's going to be too long before that screw loosens-off, and the split second it does..... No earthing to that chassis. NAUGHTY! :-O I'd be straight in there to make a dedicated earthing connection from that earth wire, to the little removeable casing/terminal cover, and the base of the chassis onto which the outer casing is connected.
(2) What's all that hot glue around that power cord in there? Subjecting that cord to that kind of thing could've damaged the insulation inside the power cord. Let's hope they tested the cord's integrity before it left the factory.
(3) Fuse. That would be better on the output than the input. From what I have heard, if the fuse is on the input side, it can be perfectly possible for that fuse while under load to be only seeing 3 or 4 amps, but the output could be pulling a good 25A through the brush, (especially if the test subject faults-out or goes hard-short) and that's when you start blowing windings and popping brushes. I'd re-configure the wiring in there so that the fuse is on the output side. Better still, have two fuses: One on the input wire and one on the output wire. The bets are on that, should you ever accidentally overload that variac, it'll be the output fuse which pops first. :-)
(4) Output voltage. Obviously speaking, what you get out of the variac does depend on what is going into it to start with. If I was going to "re-calibrate" the dial on top of the variac, I'd want to calibrate the input voltage first, as you obviously can't re-position the input wire to the windings in there to pull things into line. If your input voltage is supposed to be say, 120v and you're getting 122v or 118v, that will affect your output. Calibrating the input voltage could be done with another variac, by turning the first one upto a certain voltage, of which is measured by a calibrated volt-meter, then once you're happy with the input voltage to the second variac, then start working on "re-calibrating" the voltage plate on top. I'd keep the volt-meter on the output of the first variac, just in case a regional voltage variation occurs during the recalibration of the second variac. That way, if the regional voltage does drop off a couple of volts or increase by a few, you can 'pull-in' the calibration voltage merely by tweaking the dial on the first variac so that the volt meter reads your desired calibration voltage once again. While I understand that everyone doesn't have the luxury of owning two variacs, it does help if you really want to go into very precise voltage calibration. Then, once you have 're-calibrated' the voltage plate of the second variac, don't forget to write on it somewhere what the calibration voltage was. :-)
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Overall though, it's a cute little device. I wouldn't rely too much on that built-in volt meter though. :D
-BoomBoxDeluxe.
Thanks for the review. I've got variacs all over at home and at the lab. I use them for soldering irons, as you said, plus Tesla coil, incandescent light bulbs, window fan, home made variable power supply, and countless other applications and experiments. Just used one yesterday to test a FWBR.
Hi, just to add regarding the voltage not equal to the dial. In most cases you will find it will only be equal when the input voltage is correct to the system! ( eg. System equals 120v and calibrated @ this voltage from factory) So if the input is not 120v the dial will be out to the output!
The inaccuracy is probably because of variations on the mains. Don't know about the US but +/-10% is allowed here, I think.
Always a joy to see your vids :D
The scale on the Variac dial is % of input voltage, not absolute voltage. Your input voltage is 115V AC (or whatever) not exactly 100. That explains the offset you're seeing and why your own meter agrees with the built-in one.
Hi,
I acquired my variac pretty much in the same period as you did you clip, however this is the first time I see your video about the variac on UA-cam.
I did modify the wiring so that the fuse is actually protecting the variac's output. Afterall, the variac's input is protected via the circuit breaker on which it is connected. If someone really wants to make it safier, a fuse on the input and one on the output is an alternative to consider too.
As you stated, and also reported by other buyers, the ground connection wasn't adequate. This is one of the first thing I checked when I acquired the variac and fixed it ASAP !
I would appreciate if someone could tell me if they experienced breaker trippings because of the inrush current when they turn on the variac ?
Even if the dial is at the lower setting, no load, the breaker trips when I turn on the device. This is fairly annoying.
Some hobbyists are using the light bulb trick to minimize the breaker tripping, but personaly I'd rather prefer a more genuine soft-start approach. Would you have any suggestion in that regard ?
Finally, I ordered a small panel voltmeter that I will make fit in place of the analog meter. There is someone on UA-cam who did that modification, however it works in a similar way as your Watt meter, showing the reading around 40V and up. On my end I opted for a meter requiring an external source to operated, therefore I'll be able to see the reading in the lower ranges.
Keep up with the good work !
You might want to try installing a thermistor like orbiter8(John) did to solve this problem with his variac.
ua-cam.com/video/Avsua8G7Vpw/v-deo.html
Great video! Thanks for this. I can see I should open mine up and look at all the things you mentioned looking out for. $99 for 20 amps is a great deal. Mine is fused at 3 amps and I think it cost me around $70 new.
I use mine to feed my 24VDC power supply, so I can vary its output between 0-24VDC. Then I can plug my 30kV DC high voltage power supply into my 24VDC power supply, so I can vary that too.
Good review thank you. I wondered why there was no CE, CSA or other symbol to verify it passed. This one would surely fail, just on the ground connection by itself. It looks pretty good otherwise, I wonder why they didn't bother with a simple screw and wire to the chassis to attempt to get certification. For a lab device the calibration of the meter isn't important, most of us would measure that directly with a scope or MM anyway.
Wish you would have shown the bottom of the unit so we can see how well the shaft is supported without a bearing like most other Variac's. The one I had there was problems with the knob having side to side play allowing the unit to lose connection between the brushes and the top of the transformer coil, even allowing some small sparks inside the unit.
I have an old adjust a volt standard electric variac. It will do 0-140V AC up to 7.5 amp. When I got it it had an really old 2 prong un-polarized plug. I redid that with a 16AWG 3C cord from an old microwave, then just took a 3 prong adaptor and bonded the ground to the metal frame. I then got a 7.5 A breaker to replace the fuse holder.
I fin interesting at one time I thought variacs were just some wacky part with not much use. I use it like all the time now though, I really like I can use it to test transformers. If I put 2V in and get 10V out then I know the ratio. One time I needed 480V for a project I connected an old microwave transformer to the variac then turned it up to like 20V and that gave me 480 V from the MOT.
The other day I used it I had had to test a transformer with a 208V primary. I had another one that had a 120 primary and 208 output. I took the 120 input connected to the variac for adjustment reasons, then wired the output 208V to the input 208V of the transformer I wanted to test.
I also have an accessory I made that has a lone cord for the variac on it then that connects to a bridge rectifier heatsank to the metal box. The output then attaches to a filter cap and terminals. The other thing I use with it is an old 18AWG 3C cord with 3 insulated aligator clips on the end. Then I can clip to transformer leads, motors, etc and run them on the variac.
Last week I got 4 variacs that came from a control panel setup. They were rated for 3A at 280V. I wanted to find if I could use a different setup to input 120V and get the proper range still. I used the variac I had and my test lead to test various connection points on my new variac to find the best connection for a 120 input. In a way I find that funny because I used one variac to test a different variac.
I also used to drive an old ignition transformer from an oil furnace to make a jacobs ladder. It I had the gap a bit too big I could boost it to 140V, or bring it online slowly to see what happens. Thay can also be used with AC to control amperage because it is basically a variable inductor.
My next project is to take 2 of the 4 variacs I got install them in a metal toolbox, use one for voltage adjustment and the second for amperage control. I may put a few switches in too to adjust the primary windings on the voltage variac, and maybe another to bypass the amperage control variac. The outputs would be AC, then also have a DC output with a rectifier and filter cap(s). Perhaps at some point I may think about adding a regulated output too. These variacs are only rated 3 amp, but from what I have heard many places if you cool them fairly well you can overload them a good deal. unless it gets to be like 10+minutes, etc.
I know this is an old video but I wanted to comment for possible future viewers. I have an one Adjust-A-Volt as well. Mine is a 15 amp version. I’m pretty sure that the dial is marked in percentage of the total output voltage, and not in actual voltage. That’s why it never matches up. If I remember correctly, when I tested mine , by percentage it was in the ballpark. +/- 5% I believe.
if your set brush at 120volts does tgat mean 120 wraps of wire at that point? if not what does determine the voltage relitive to the number of turns?
Thanks for the info, I recently found a powerstat 246 variable transformer while cleaning out a barn, unused still in the box. I had no idea what i was looking at, now I just need to figure how much it is worth.
Enjoyed the video. Does the engineering calculator not run off 120 volts? How was it originally powered?
Nice review. My thoughts:-
* If the wires were spade connected, some clown would probably re-install them arse-about.
* Can you could lock the knob properly onto the shaft flat, and then fix the zero offset using the set screws on the wiper collar.
* I would install proper ground wires to all 3 chassis parts, also putting some extra length on the wiring inside the power cover.
* Maybe some hot snot would stop the output sockets flapping about.
My 25-year old Tenma variac has exactly the same non-linearity with respect to scale markings. I adjusted it to be more accurate at the higher end.
@Eric William, Thanks. True, 210mA seems low but it was a Harbor Freight item so maybe its broken. I ran my 5Hp air compressor at ~14A for 10 minutes on the variac and the variac didn't even get warm. Nice.
Hi Todd, wanted to ask you a question about using a variac to lower the voltage of a 100 watt Marshall guitar amplifier. How many amps rating would you need, 10A or 5A at 500 watts like the SC-5M model sold from China that looks like the one you have? My amp uses a 4amp fuse. My other 50 watt amps use a 3 watt fuse.Hi Most people say you should buy an old Staco variac made in the USA. how do you find the quality of these Chinese variacs? I would appreciate your expertise on which variac I should buy. I searched all over UA-cam and the net and still haven't found the answer to my question. Thanks Michael Newell from Niagara Falls, Ontario, Canada
Find the rating of the input to your amplifier (usage rating from mains). If that is only 100 watt or less then the 5A china variac will work just fine. Just make sure the amplifier input is less than the rating for the variac and the china variacs are fine.
Are those copper winding live would you get shocked when its on and touch it by accident without the case?
Yes.
did you measure the inductance of the primary? I guess is high, maybe Henry's but I have no idea how big.
I think that I would glue a clock hand to the bottom of the knob. That would give you a more precise and much easier to see adjustment indicator.
Todd I bought a variac and am having some issues. I’m outside my return window so I’m going to have to deal with it. Can I email you some pics of what I’m working with? Thanks in advance.
Sure, My email is in my About Me page at ToddFun.com
That 110V variac would work on 240v mains, wouldn't it? Only the scale on the dial would be wrong and the little volt meter would go "pop".
Or would the variac windings get hot and melt? If not, is the only difference between a 110V and 240V variac the label on the dial and the little voltmeter?
I think that for every given position of the dial the output voltage will vary depending on what load you connect. The bigger the load (lower impedance) the lower the output voltage will be. Just a reminder. Great video BTW, keep up the good content.
EDIT: I just realized after this vid that autotransformers are just variable inductive voltage dividers. en.wikipedia.org/wiki/Voltage_divider#Inductive_divider
I assume you meant "compared to no load" instead of no variac. Interesting that it doesn't vary too much with a load. Good job testing it to make sure! that's not a serious difference in voltage and I probably wouldn't mess with it either.
How do you find that CSI3005X power supply in the back ground. have you done a teardown and review of it?
+MonkeyMagic Elecifun I have done a tear down but not on video. It doesn't have as many features as say a the "RIGOL DP832" (astore.amazon.com/tod0f5-20/detail/B00ENX02GC) but the "CSI3005X" (www.circuitspecialists.com/bench-power-supply-csi3005xiii.html) is still very usable and I have had no troubles with it in all the years I've owned this unit.
***** I had one but killed it within a couple of weeks. It would be great to see a tear down of it. Circuit Specialists over here (UK) asked me pull mine apart to find the fault. I did and did, but I didn't like the lack of features, Output button,resolution, current control to name a few. I bought the Rigol DP832 and have never looked back.
PS I think your Auto Transformer review, tear down is great, I am looking for a not too expensive unit and think I may have found it. Cheers.
I plugged a receptacle ground tester into mine and under 60v it's says the ground is fine but anything higher it says it has a bad ground. I even scratched of the powder coat off around the ground lug & it still does it, any idea why?
Not right now. I will test mine tonight and get back to you with any ideas.
This is an auto transformer and your receptacle tester needs to measure the ground leg through the neutral leg. Maybe your neutral and hot are switched in your wall receptacle or in the variac plug or in the variac wiring or at the service panel. I thing this would cause your problem as it may not like the value it gets through the windings of the variac if the neutral is on the hot side going into the variac windings. That said, your tester shouldn't even be able to power on until after the variac gets over 60v AC as that is what it takes to turn on the 110 V Neon Indicator Lamps normally found in such receptacle tester plugins, this makes me think you have some bad wiring. I tested my variac with my 110 V Neon Indicator Lamp receptacle tester and it stayed off until 65 V AC then turned on with one light stating bad ground, then at about 80 V AC to max AC voltage it showed two lights indicating all good. Hope that hepls
Todd Harrison weird, it seems like the 10amp model is nicer. Thanks for testing yours too!
I didn't like those crappy ground connections either. And I think "common" applies more to DC circuits. I think "neutral" is best for AC. Your review was good, very thorough, almost Dave Jones-y. Include a ToddCAD schematic and it would be perfect as a variac introductory tutorial. I learned a few things from the historical perspective. Glad you like my videos! Have some plans to do a few more JT experiments using optoelectronics. What's up with that CCFT power supply in the background?
Great video! I have the SC-10T which is rated for 10A and is isolated, but the front panel is identical. I'm planning on modifying it to add a digital display with an ammeter and volt meter. Did you notice that if you pull the fuse, the light on the switch stays lit. They have the fuse after the switch (between the switch and transformer). Doesn't make much sense to me.
+swappart.com I was not aware they made such a think. Thanks for sharing. I have added it to my Amazon store: astore.amazon.com/tod0f5-20
+Todd Harrison (ToddFun) I just lucked upon it while looking for an isolation transformer. Since it was fully isolated, and I'd wanted a variac anyway, I went for it. When my parts get here and I get my modifications done, I'll post a link to pics.
+Todd Harrison (ToddFun)
Hi Todd,
I went to the store link above and it says "Note - The grounding pass through and bypasses the isolation, which means the grounding isn't isolated. You may be able to use a 3 prong to 2 prong grounding converter."
Does that not mean that it is not isolated? If it is, then you should not have to use a 3 to 2 prong converter. Did you have a chance to measure the output wires to ground? Also, could you help explain how they managed to isolate it with only one coil instead of 2 coils i.e. a primary and secondary as in a transformer? Thanks.
+istoreit Thanks for the information. They have changed the product that this links to so I have removed it from my store listing. The one it was linking to was not isolated. I did leave other isolation transformers on my Amazon store that are not variacs. You can get a good Variac and plug it into an isolation transformer to get the same combo.
Hi Todd,
Thanks for the review of the variac. I was on the market for one and found your review and helped me pick the same one you have. On bit of good news - the company must have reviewed your comments and added a earth ground wire to the cage! I took mine apart to check the quality and when I took off the front panel, they had already added the extra Earth connection over to the cage (I did add a star washer to make sure there was a good electric path through the paint).
Thanks again for the review and take care,
h
+h barton Thanks for the comment and the update on the earthing wire. That is good to know they fixed that issue.
same lines as you mentioned of powering up a commodore.
powering up older test equipment to make sure you don't blow it up.
Always a good idea.
Just curious Todd; did the scale get any close with a load on the output?
your voltage at your house will vary seasonally making your top outside scale wrong season to season, building to building, electric supplier to supplier. metering is a must.
Also, check the outlet your using for proper ground connection with a test plug before using.
The dial on top loses accuracy at higher output voltages because your variac is rated at 110V, and you're inputting 120
Thanks
210 milliamps for a wood burning iron? I would have expected much higher. Gread vid and great piece of equipment. Cheers
Great video. Mine never worked right. I used your video to clean the coils, remove the armature, adjust the tension rings, reset the armature and reassemble. It works much better now
I'm very glad the video helped you with your repairs.
Another awesome video sir, I recently acquired 2 Superior Electric Co 3PN116B Powerstat Variable Autotransformers off ebay for 5 bucks a pice! Score ob my part, just need to replace old dry rotted cords. I did have a question for you about the scale on these units. The two i have go from 0 to 100 marked, but output 0 to 140 volts, as well as all of the pictures i have seen show a scale of 0-140 volts on them. Is there something odd about the ones i have, or else i have no clue! I took the covers off to check the windings, and the screws appeared to be the original ones. Any guess as to why the output would be labeled this way as to the others i have seen?..
Ray M I don't know why the label is 0-100 unless it is just for a % of output. 0% to 100%. I have seen them with 0-100 but they where the 240v model. maybe somebody just modified a 240v unit to 110v. You could etch your own from some copper plate or make one by hand. Also try to see if the plate flips over, maybe the back side has 0-140v ?
***** I am not even sure how to tell if it is a 240 volt model or the 120 volt one, other than the model numbers. I will try and attach a few pics of the two, but also the rivits in the caps of these original scales appear to be the original ones.
***** ok, just realized I cant attach pictures. .. uggh
Ray M I'm thinking it is the 240v unit that may have had the plugs modified. But you can still put 110v in.
Excellent video. Shouldn't be too hard to modify a digital volt meter into the variac instead of the needle meter.
Did you try adding a load?
I bought the exact unit, a 20 amp dual plug outlet model, and it came in all bent up on one side, ...seems to work okay though.
I think I would have sent it back or claimed shipping damages. My AT's fuse completely destroyed itself for no apparent reason so I bypassed it for now, but I really need to put a new "better" fuse holder on it.
Yeah, well, its a cosmetic issue I suppose, I could take it apart and straighten out the metal a little bit better. The problem I believe was that it was too heavy for the thin foam on the bottom, and that is what happened, that it got thrown around and it slightly buckled on one edge, that is what bent in the metal on the round shape. Hey, I tried to avoid this bs,...I noticed the seller was supposedly in California, and I am in Oregon, then when it was shipping it comes from Kentucky,...I messaged the ebay seller, who seemed like a chinese foreigner about this and received a strange foreign like english apology. I paid $76 + $15 shipping, and I alerted the seller what happened, haven't heard back though, and sending it back for an exchange just seems a waste of time, and they are now out of these. Now I have a chinese 30 v 10 amp dc power supply coming from a different seller,....in supposedly chino california, another one of our chinese sellers on ebay, I hope it comes in straight. *****Just got an email from the seller, wanting some pictures of the damage, which I gave, maybe I might get a partial refund, but most likely, in the past from other ebay sellers on partial refunds on chinese made consumer goods, I get a five or ten dollar partial refund while they claim a total insurance payout from the shipper,....I have seen that twice. BUT, the point here is, .....I'd expect the heavy 20 amp variac to be twice as likely damaged or bent up in shipping cause the thin foam on the bottom of the box is too thin and pancakes out in no time allowing the heavy item to be slammed on concrete and other hard surfaces with little protection other than pancaked bottom foam and thin cardboard. Like I said, I have a el cheapo 30v 10 amp dc power supply coming, supposedly from Chino California to southern Oregon(here) from a different seller, and if that comes in all squashed or bent up,....haha, I might need some electro shock treatment so to speak.
What they told me in school was that you can never rely on the scale on top of the variac. The input voltage may vary and when the input voltage is not exactly right, then neither is the output voltage. For an accurate voltage reading, use your own volt meter and ignore the scale.
I think the grounding is a big fail! And I don't think your fix is good enough either; the mains ground should be securely connected to ground lugs mounted on unpainted areas of the panel and the main enclosure.
Does it become more accurate with a load?
if u unscrew and flip over the scale it may have percentage rather than voltage markings
Where is outputnya mr?
Hi
I got mine today, a vevor with digital readout. A 3kva 240 volt. But the output is enormous! 338 volt 😃😁
With shipping to DK only 99$.. These things has becoming really cheap.
About using it as a transformer, just remember: It has live mains, there is NO isolation, so one's power supply is LIVE on the low voltage side....
I just purchased two of these variacs from Circuit Specialists because of the video.
JJ91284 I hope they work out for your. I'm sure you will have to make the same changes I did.
Thanks Todd,You are a great teacher.Keep it up.safe from South Australia
safe ur rahman Thanks. I learn a lot when I make these video too. I want to get everything as correct as possible so it motivates me to learn more making the videos than I would have otherwise known about the product.
maybe a cool mod would be to change the analog meter out for a digital meter.
This was a great review / tear-down! Nice work!
Todd, your pesky visitor must have thought the video was going to be about flyback transformers.
Prolly it'd be fine, ofc without the volt meter. You'd have to interpret the scale as a percentage scale.
Btw for the same power output in a 230v line you require half the amps you'd need in a 110v so you wouldn't need to bother about the fuse either.
I believe you have hit the nail on the head here. The scale is a percentage scale. If the scale shows 100 at the 1:1 point (110 VAC in 110 VAC out) surely that's the case. Being a percentage scale means that it 'works' irrespective of the input voltage.
I had a VEVO and it is th same exact model. I sent it back because the wires were super crappy .
Yes these can be doggie sometimes
I don't think there would be enough winding inductance for 240v.
Great video, very interesting, good job your lad was there to remind you that you were still recording LOL, many thanks.
what is a chasy? or how u spell it...
You would call any foundation box or support structure a "chassis". In this case the autotransformer circuits are in a metal chassis.
Take care mate....looking forward for more:)
Yeah, non linear scale was pretty weird. Must have been a design goof! :)
It's not a voltage scale, it's a % of input voltage scale. Look at it that way and it's exactly what you'd expect it to be.
The sockets look like a surprised face 😂
thank you this was very helpful. you know if you go after that fly and kit it will be an entertainment by itself.
Liked the video but there is a lot of info that is redundant. I liked it don't get me wrong but you need to do some editing. Other that that I walked away from this with a good understanding of the unit. P.S fly paper or bug zapper will take care of that fly.
The name came from "Variable A/C"
I Like your presentation, Thank you for telling us what is a VARIAC . Great video.
PSS, didn't know you are in Az.. Hello Neighbor, I'm here in Surprise Az.
thanks
I real like this
Great video, Todd, but 'Chinky'?! That's a word your videos can do without.
chintzy is probably the word you were looking for
19:05 wtf was that jajaja.
Zooming sounds manual overlay ;)
Think s
You're welcome Elec.
I got one for 5$
Your initial explanation of an AUTO TRANSFORMER IS TERRIBLE.
Take some advice, Soend some time planning what you will say BEFORE STARTING YOUR PRESENTATION
Please post your explanation in the comments so everyone can learn from you and I'll pin it to the top.
@@ToddFun The presentation appears to be an off hand unplanned performance.
As I stated in my first comment there appeared to have been done without ANY FORETHOUGHT.
@@ToddFun Hey CALM DOWN, you obviously do know your subject BUT IT EAS NOT WELL PRESENTED.
You need to plan the presentation and PRACTISR IT FIRST.
@@ToddFun It's always worth a chuckle to see people give instructional advice when they don't post videos themselves. Lots of armchair experts who don't understand how difficult it can be.