I see a few others also asked about the Variac. It appears to be something similar to the Staco Model 221-B. That one is rated at 2.5 amps. They go for around $160 new. Finding a used one (that is in good shape) could be a challenge. You might be better off buying a cheapo variac from eBay (~$50), removing it from the case, using the other parts, then building out the layout Terry has done by adding the panel meters, switch for Line vs Variable Output voltage, etc.
Terry, You might have mentioned that one must derate the variable transformer current on the lower voltage area of the transformer, because of the I.M. that came with a NOS Variac (R) I bought, it stated that "the amp rating was spec'd over the entire rating of the auto-transformer, and one must derate the current unless using the entire winding," I have built several of these over the years, and I always include an isolation transformer in the construction. This is because I work on a lot of hot chassis radios and TV sets. Failure to use an isolation transformer on the equipment under test can result in a big "Bang", and can damage the equipment under test and the test equipment too. (I had this happen back in Tech School when the teacher failed to teach or tell us anything about "Hot Chassis" sets and I connected the ground of a scope to the AC/DC TV set and blacked out the entire classroom building. Gotta love teachers that only knew theory, and had no practical experience).
Nicely done Terry. A tip for you guys out there looking to do a conversion like this without a mill. got a drill press or even a corded power drill? Screw your front panel down to a scrap of 3/4" plywood. Mark your hole centers and use a plain old hardware store hole saw and arbor. the plywood will keep the panel stable. Use your slowest speed and a bit of oil. You'll be surprised how nice a hole you can get with simple tools! Keep them killer vids coming D-Lab!
Nice project. One little suggestion is to add a neon bulb where the empty hole is for the + terminal and wire it to the output of the variac. When you set the voltage above about 60 volts, the neon bulb will illuminate indicating high voltage. Just a little safety feature addition.
TIP: If you can't find one of those older Hubble outlets, just buy a single round outlet at Home Depot or Lowes. Use the plate 6-32 holes to mount and cut the rest of the bracket off on each end.
Hi Terry, Well, I think I will go ahead and build myself one of these. I do think I will add the so-called "dim bulb tester" since I can be bit of a dim bulb myself sometimes! Thanks for sharing.
Terry, thanks for the information on the metered power supply! I have been watching your videos for a little while and I love them. A real education! Merry Christmas!
In the 70's I built a 10a version of this in a slope faced crinkle finish. The one it had was a 1000 watt isolation transformer. A lot of the TV's back then had a hot chassis so line isolation was important to me. Recently the 0-150 voltmeter opened up so I bought one off ebay, it doesn't match the 0-10a meter but works just fine.
I think the point of an isolation xformer arises if/when you’re working on series filament radios/amplifiers or when you have test equipment you want isolated from mains voltage
Good job Terry. Another great tutorial. I like how you pulled up the watch band. Top notch practice. Safety 1st. Happy Holidays to you and Yours. This is way better than the guit ologist. I live for the tube anything and everything approach. You don't have to learn how to play guitar of anything else for that matter cuz you are doing fine.
Great video. It would be super cool of you did a basic one about building the audio dummy load meter setup you made. That would be a great addition to peoples bench for these type of repairs/troubleshooting for output visuals all in one box Thanks for the content and info. Your legacy lives on in us
From Leo: I have always been "gonna get a variac". I have been using a lightbulb socket on a board since the 1960's. It is safety, but does not help with diagnosis. I have let the blue smoke out of a few components along the way. Anyone playing with electronic repair should have a variac. I may still build one.
I plug my variac into my "wattmeter" to see the current draw. Not as good for a few reasons but it adds the metering visibility. Plugging the wattmeter into the variac output can be more useful but low voltages may not display.
Looks like a great home project. I believe I have all of the major components necessary to do this already. I have a suggestion for a future video that would help with the un-trained/self taught hobbyist like myself. Would you demonstrate how to calculate what the proper amount of current draw should be for an amplifier that does not have a schematic or specs? How does one know if there is actually too much current draw and likely suspects for shorts? Your consideration is appreciated.
This was excellent, just what I was hoping for! Thank you Terry! Now the hunt begins for some parts. Hope you and family have a Merry Christmas and Happy New Year!
Battery eliminators on eBay are more expensive than the variacs... :( Mind you, everything is overpriced on eBay... Season's Greetings Terry, thanks for all the content in 2019. Cheer,
I appreciate all the great videos you produce and upload. I would really like to see you put an isolation transformer in the circuit though. It would be a big help to all who are interested in this unit.
Merry Christmas to you and your Family! Santa's coming on christmas eve to Sweden and I'll remind Him of the tubewizard whith the big heart in the USA.
Just picked up a General Electric T-127b and cant get any schematics and it's a nice little 30 watt 5 tube AM radio, was going to do a conversion into a little guitar amp, it just hums VERY loud when it warms up, noise just gets more gritty when you turn volume but the volume doesn't change and it does it on zero volume, also makes a weird spacey underwater noise when playing with the tuning dial lol
i had some hum issues like that with steel chassies. They create a great big magnetic field around all the electronics and it couples into the speaker. nothing really helped my situation but then again yours might be different
When I saw the thumbnail and read the description I was hoping you were going to be working on a Henry RF amp cause it looks like one :-) Merry Christmas. Have fun out here.
Thanks for the DIY. It so happens I am building a variac and needed some clarification on a few things, like why an isolation transformer is not needed. Now all I need is a vacuum tube tester, any suggestions for a limited budget?
Nice work! Looks really cool. Btw have you been doing much with CW and transceivers lately? I ended up building an Elecraft K2 recently. How's yours going?
Can the pilot light be converted into a dim bulb tester using a small bulb? Or, simply add a small bulb in the "Positive hole" that is covered by the label?
Hi and good day. As normal you have done it again. Great useful unit bulid. ? Due you sleep at night ? Your brain must be ingage to come up all these great projects. Thx for a great video
Ge, I don’t know, you can buy a varianc cheaper than you can trying to build one, and especialy going through all the trouble of buying all the parts plus the modification work, but I guess just for a project I guess it’s ok, I would rather use the money to buy a few drinks or something, CHEER’S .🍸
So I built one like this, but when I test it with my soldering iron, the volt meter drops down quite a lot, like under 50 volts. Why would that be? Thanks for any information.
Hey Terry, I disagree that it doesn't make sense to use an insulation transformer for a lab like yours - or mine...! First, amps have an exposed area of line voltage, that you might accidently touch while working in an amp... Second, you might work on other electrical devices as well, that don't have a power transformer... In my opinion it's the wrong spot to save money and NOT go for an insulated variac... I built a device almost like yours about 10 years ago, and I use it almost every day. It's one of the most important devices in my own lab. But I used an adjustable transformer that has insulated primary / secondary windings. It's way bigger and heavier than the one I can see in your video - so probably also more expensive - but I am really lucky to have this extra safety of a not-mains-related power outlet at my workbench!
Nice video. I'm glad you used a non-functional unit to convert, I always picture someone cringing when a working unit is "murdered" and they wanted it. I don't have a continuously variable variac like you created; instead I've got an old multi-step one with horizontal and vertical position slide switches, giving 9 possible output voltages. I think it's a B&K unit, saved it from the dumpster many years ago and only used it a few times. I need to find where I stored it and have a look. [ Edit - Apparently it's a model TR110 Isolation Transformer, so as I said it's not really a true variac. www.bkprecision.com/products/discontinued/TR110-isolation-transformer.html ]
ooooohhmg u rock i did this same project with simple dc motor push buttons for forward reverse polarity to go up down voltages u cant imagen the transformer is basically made for stabalize 220 v in any case cuse iam from pakistan and commpany was puma i alter its winding little bit how could i send u my project vedio i wana show u my project of trouble shooting technics su7600 long tail diffriential stage was netrous that was some time gives 5 v dc while working only in left channel ....cuse ocl and pure complimenty so dv was prob i did it ....and 2nd was sharp optonica sa2121 receiver
Thumbs down for making a blanket statement that an isolation transformer is not required/necessary. Anybody who has a 220V or higher supply in their country should absolutely incorporate an isolation transformer for safety. Also ensure that the mains on/off switch has suitable double pole isolation ( 3mm contact gap in UK).
What? No 120VAC front panel metal binding posts? Keep it period correct. OK, chill everyone. Just being silly. I've got about 3 stand alone Variacs but what I'm missing is a pair of meters. No idea why I haven't cobbled something together. Got a small one too that could be mounted in a box.
From Leo: Generally yes, but if your amp draws over 2 amps, that is not what you need. The 5 amp ones are only a little more money, I have never needed more than that on electronic equipment.
![ออกพรรษาน้ำตาหล่น - แอน อรดี [OFFICIAL MV]](http://i.ytimg.com/vi/PFZtOcY9ONA/mqdefault.jpg)
I see a few others also asked about the Variac. It appears to be something similar to the Staco Model 221-B. That one is rated at 2.5 amps. They go for around $160 new. Finding a used one (that is in good shape) could be a challenge. You might be better off buying a cheapo variac from eBay (~$50), removing it from the case, using the other parts, then building out the layout Terry has done by adding the panel meters, switch for Line vs Variable Output voltage, etc.
Busy putting one together.
Thanks
Terry, You might have mentioned that one must derate the variable transformer current on the lower voltage area of the transformer, because of the I.M. that came with a NOS Variac (R) I bought, it stated that "the amp rating was spec'd over the entire rating of the auto-transformer, and one must derate the current unless using the entire winding,"
I have built several of these over the years, and I always include an isolation transformer in the construction. This is because I work on a lot of hot chassis radios and TV sets. Failure to use an isolation transformer on the equipment under test can result in a big "Bang", and can damage the equipment under test and the test equipment too.
(I had this happen back in Tech School when the teacher failed to teach or tell us anything about "Hot Chassis" sets and I connected the ground of a scope to the AC/DC TV set and blacked out the entire classroom building. Gotta love teachers that only knew theory, and had no practical experience).
NOS
is not a brand
it stands for New Old Stock
If you do a lot of radio repair work, especially on All-American Fives, an isolation transformer is definitely recommended.
Nicely done Terry. A tip for you guys out there looking to do a conversion like this without a mill. got a drill press or even a corded power drill? Screw your front panel down to a scrap of 3/4" plywood. Mark your hole centers and use a plain old hardware store hole saw and arbor. the plywood will keep the panel stable. Use your slowest speed and a bit of oil. You'll be surprised how nice a hole you can get with simple tools! Keep them killer vids coming D-Lab!
Nice video Terry..
Nice job..yes you can buy it..but what fun is that..thanks Terry....
Nice project. One little suggestion is to add a neon bulb where the empty hole is for the + terminal and wire it to the output of the variac. When you set the voltage above about 60 volts, the neon bulb will illuminate indicating high voltage. Just a little safety feature addition.
TIP: If you can't find one of those older Hubble outlets, just buy a single round outlet at Home Depot or Lowes. Use the plate 6-32 holes to mount and cut the rest of the bracket off on each end.
D lab logo to hid the extra holes or some aluminum rivets would look cool, Nice job Terry (D-Lab).
For a future improvement you may want to consider adding an isolation transformer so the output is isolated.
I have made the same thing, using an old
60's-70's DC variac with the same meters. Removed the rectifier... Bam! Works perfect.
Very nice project Terry. What a money saver, and to boot, a good entry-level project for those new to construction techniques.
Hi Terry,
Well, I think I will go ahead and build myself one of these. I do think I will add the so-called "dim bulb tester" since I can be bit of a dim bulb myself sometimes!
Thanks for sharing.
Terry, thanks for the information on the metered power supply! I have been watching your videos for a little while and I love them. A real education! Merry Christmas!
Watching this while I cook . Man iam addicted. This explains why iam single. Oh well i will keep watching while petting my cats.
In the 70's I built a 10a version of this in a slope faced crinkle finish. The one it had was a 1000 watt isolation transformer. A lot of the TV's back then had a hot chassis so line isolation was important to me. Recently the 0-150 voltmeter opened up so I bought one off ebay, it doesn't match the 0-10a meter but works just fine.
Excellent, thanks Terry.
I think the point of an isolation xformer arises if/when you’re working on series filament radios/amplifiers or when you have test equipment you want isolated from mains voltage
Yup. Indeed if combinate with working with a scope when you need no ground relation with your neutral.
super useful for troubleshooting switch mode supplies as well
It’s looking great Terry, well done! I like all your videos! always very interesting ! Grz
Good job Terry. Another great tutorial. I like how you pulled up the watch band. Top notch practice. Safety 1st. Happy Holidays to you and Yours. This is way better than the guit ologist. I live for the tube anything and everything approach. You don't have to learn how to play guitar of anything else for that matter cuz you are doing fine.
An interesting project. Thanks for adding the schematic to the video.
Great job making a repurposed equipment into a Variac.
Great video. It would be super cool of you did a basic one about building the audio dummy load meter setup you made. That would be a great addition to peoples bench for these type of repairs/troubleshooting for output visuals all in one box
Thanks for the content and info. Your legacy lives on in us
Michael Sorenson he has already done a vid on that :)
Terry point to point is great for electronic circuits but some tidy looking would look much smarter with this job.
Great job anyway.
Nice job Terry!
Hey Terry you could add a light socket where that spare hole is for the current limiter bulb as well. food for thought?
From Leo: I have always been "gonna get a variac". I have been using a lightbulb socket on a board since the 1960's. It is safety, but does not help with diagnosis. I have let the blue smoke out of a few components along the way. Anyone playing with electronic repair should have a variac. I may still build one.
Nice and simple. Thanks, T-Man. And a Merry Christmas & Happy New Year to you and our family!
I’m heading to my basement where I keep my Bridgeport and Greenlee punches...wait - I don’t have a basement...
I plug my variac into my "wattmeter" to see the current draw. Not as good for a few reasons but it adds the metering visibility. Plugging the wattmeter into the variac output can be more useful but low voltages may not display.
Looks like a great home project. I believe I have all of the major components necessary to do this already. I have a suggestion for a future video that would help with the un-trained/self taught hobbyist like myself. Would you demonstrate how to calculate what the proper amount of current draw should be for an amplifier that does not have a schematic or specs? How does one know if there is actually too much current draw and likely suspects for shorts? Your consideration is appreciated.
i have no youtube channel but u make me think about it
This was excellent, just what I was hoping for! Thank you Terry! Now the hunt begins for some parts. Hope you and family have a Merry Christmas and Happy New Year!
I have a Heathkit IP-12 here along with a set of the matching meters, no Variacs though
D-lab Electronics Hi Terry! Oh really? That is interesting ... how does a guy like me find out the cost?
D-lab Electronics :)
Great Job Terry
thanks for the advice
Excellent! Merry Christmas, Terry!
Thanks Terry! Merry Christmas!
Nice build Terry. Merry Christmas to you and your family.
Battery eliminators on eBay are more expensive than the variacs... :(
Mind you, everything is overpriced on eBay...
Season's Greetings Terry, thanks for all the content in 2019.
Cheer,
I appreciate all the great videos you produce and upload. I would really like to see you put an isolation transformer in the circuit though.
It would be a big help to all who are interested in this unit.
That was cool. Maybe I should try and build one. I have a tube amp and may need to work on it some day.
Merry Christmas to you and your Family! Santa's coming on christmas eve to Sweden and I'll remind Him of the tubewizard whith the big heart in the USA.
Very good vid as usual. Nice year on your channel. Thanks
FELIZ NAVIDAD Terry and family!!!! GL 73,s
Thanks Terry!
Nice video, thx Terry
Just picked up a General Electric T-127b and cant get any schematics and it's a nice little 30 watt 5 tube AM radio, was going to do a conversion into a little guitar amp, it just hums VERY loud when it warms up, noise just gets more gritty when you turn volume but the volume doesn't change and it does it on zero volume, also makes a weird spacey underwater noise when playing with the tuning dial lol
I've been binge watching videos from your channel and I bet I sound silly while you're like, "yep, filter cap again" lol
i had some hum issues like that with steel chassies. They create a great big magnetic field around all the electronics and it couples into the speaker. nothing really helped my situation but then again yours might be different
Mine is like this lol
th-cam.com/video/vR7v0gs_asc/w-d-xo.html
I took the back off, burnt up tube
Really helpful Terry, thank you so much !!!
Ficou excelente essa montagem...Parabéns colega...!!!!!
When I saw the thumbnail and read the description I was hoping you were going to be working on a Henry RF amp cause it looks like one :-) Merry Christmas. Have fun out here.
Yes Sir, it does look like that Amp, good observation.
Thanks for the DIY. It so happens I am building a variac and needed some clarification on a few things, like why an isolation transformer is not needed.
Now all I need is a vacuum tube tester, any suggestions for a limited budget?
Nice work! Looks really cool. Btw have you been doing much with CW and transceivers lately? I ended up building an Elecraft K2 recently. How's yours going?
I had a dream I was at a hamfest and found a stripped communications receiver the guy was going to give me for making a custom variac.
Can the pilot light be converted into a dim bulb tester using a small bulb? Or, simply add a small bulb in the "Positive hole" that is covered by the label?
Hi and good day. As normal you have done it again. Great useful unit bulid. ? Due you sleep at night ? Your brain must be ingage to come up all these great projects. Thx for a great video
Hey Terry, I’ve been thinking, could you use that empty hole for a Variac/Line mode indicator light? Might be cool!
Terry, it's not isolated from the mains. I found a B&K 1653 on eBay that is isolated.
Ge, I don’t know, you can buy a varianc cheaper than you can trying to build one, and especialy going through all the trouble of buying all the parts plus the modification work, but I guess just for a project I guess it’s ok, I would rather use the money to buy a few drinks or something, CHEER’S .🍸
So I built one like this, but when I test it with my soldering iron, the volt meter drops down quite a lot, like under 50 volts. Why would that be?
Thanks for any information.
PIddly detail. If you had milled the squares about a 1/8" lower, the 'frame' on the panel would show all the way around
Hey! At 5:30 I was expecting to see the punch in action!! Noooooooo! :( Anyway thank you for the great video!
Hey Terry, I disagree that it doesn't make sense to use an insulation transformer for a lab like yours - or mine...! First, amps have an exposed area of line voltage, that you might accidently touch while working in an amp... Second, you might work on other electrical devices as well, that don't have a power transformer... In my opinion it's the wrong spot to save money and NOT go for an insulated variac... I built a device almost like yours about 10 years ago, and I use it almost every day. It's one of the most important devices in my own lab. But I used an adjustable transformer that has insulated primary / secondary windings. It's way bigger and heavier than the one I can see in your video - so probably also more expensive - but I am really lucky to have this extra safety of a not-mains-related power outlet at my workbench!
The only thing we didn’t see was the installation of the power cord.
Nice video. I'm glad you used a non-functional unit to convert, I always picture someone cringing when a working unit is "murdered" and they wanted it.
I don't have a continuously variable variac like you created; instead I've got an old multi-step one with horizontal and vertical position slide switches, giving 9 possible output voltages. I think it's a B&K unit, saved it from the dumpster many years ago and only used it a few times. I need to find where I stored it and have a look.
[ Edit - Apparently it's a model TR110 Isolation Transformer, so as I said it's not really a true variac.
www.bkprecision.com/products/discontinued/TR110-isolation-transformer.html ]
ooooohhmg u rock i did this same project with simple dc motor push buttons for forward reverse polarity to go up down voltages u cant imagen the transformer is basically made for stabalize 220 v in any case cuse iam from pakistan and commpany was puma i alter its winding little bit how could i send u my project vedio i wana show u my project of trouble shooting technics su7600 long tail diffriential stage was netrous that was some time gives 5 v dc while working only in left channel ....cuse ocl and pure complimenty so dv was prob i did it ....and 2nd was sharp optonica sa2121 receiver
Terry, could you please tell me who you ordered the transformer from.
Thumbs down for making a blanket statement that an isolation transformer is not required/necessary. Anybody who has a 220V or higher supply in their country should absolutely incorporate an isolation transformer for safety. Also ensure that the mains on/off switch has suitable double pole isolation ( 3mm contact gap in UK).
Cool!
How different/difficult is it to build a variac for a guitar amp not for testing but to play the amp cranked at a low output volume?
Fantastiv Vídeo!
nice!!!
Just be careful working on all american 5 radios with an un-isolated variac
I plug my diy variac box into an isolation transformer, when I need isolation.
Sir where can i get that beautiful thing that You hold in hands in 1:33? What is that?
Where did you get the bare variac? Thanks!
Can anyone post a link to a video that shows the variac that was built in the Heathkit box?
HI T. Were did you find the Variac?
What? No 120VAC front panel metal binding posts? Keep it period correct.
OK, chill everyone. Just being silly. I've got about 3 stand alone Variacs but what I'm missing is a pair of meters. No idea why I haven't cobbled something together. Got a small one too that could be mounted in a box.
Do u have outlet in india?
is there an earth wire been added to the outlet and the chassis
I am seeing a lot of chinese variacs for sale on ebay. They are 2 amp power ratings. Are these ok for use with guitar amps?
From Leo: Generally yes, but if your amp draws over 2 amps, that is not what you need. The 5 amp ones are only a little more money, I have never needed more than that on electronic equipment.
Neat, like it. May motivate me to put mine in a cabinet. Wb4zqu
Where did you purchase the variac?
Where can you get a bare variac?
Best place, ebay or Ham Radio swapnet sites.
build one with scr
But this is not an isolation variac !
So what,use polarised plug in and out.
You could plug it into an isolation transformer box.
sooo, you're a cabinet-maker? okay. :^P***
An excellent video. It is very satisfying to create something useful for the bench. de k3oe
What? No glass of wine?
Shot this at 0800
4 or 5 hundred dollars? A variiac is only about $65 on amazone.