# Look at this stand alone rheostat dimmer I found



## Les (Apr 21, 2008)

So for years I have seen this up in the tech storage of my local community theatre. It was usually behind some junk on the lowest shelf next to the air handler and I just assumed it was some old electric dryer motor or something. Anyway a few days ago I finally decided to pull it out and give it a look and it turns out to be a 2,000w rheostat dimmer. I asked if I could have it and they said sure, since no one can remember the last time it was used. I still haven't gotten the courage to plug it in. If I do, it will probably be out in the driveway from 20 feet away with an extension cord. And into a GFI outlet. Just by looking at it I can already tell I'd like to have a heavier duty cable attached to it (like the ones used for lighting jumpers, isn't that S.O.?), which I think I have attached to this Mole Richardson light that I have. It has about 25' of cable and I feel like I only need 6. There is a knockout which hasn't been knocked out on the opposite side of the existing one, so if I would probably knock it out and run the input through one and the output through the other. And strain relief it too.

On the other hand, judging by the lack of rear (and bottom) cover (shock hazard) and asbestos looking cable on the inside shaft, maybe this whole thing would be best stripped for it's copper?

What do you think?

EDIT: Just noticed it carries a UL Label. heh. It would never pass today.

SPECS:
"Powerstat" Transformer Dimmer by Superior Electric Co.
Model/Type D2000
Serial Number 2793 
16.7 Amp

You will have to excuse the quality of pictures. Camera phone. Bleh.


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## gafftaper (Apr 21, 2008)

We had one just like that in college. Sometimes we did small shows in the lobby and we used it to run the scoop houselights. I loved it. It's probably still there too.


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## Dustincoc (Apr 21, 2008)

We have a couple of those around. Quite handy for the followspots that have been rewired(Of course, the fan, ect. is independently wired). That's what we use at our second stage. I've also seen one or two lying about the shop.


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## cutlunch (Apr 21, 2008)

Lester that appears to be an autotransformer based dimmer not a rheostat dimmer.

Here's a link that shows what similar models made by that company look like.

http://www.wimb.net/index.php?s=slosyn&page=2

Heres a wikipedia article showing how the autotransformer works.

http://en.wikipedia.org/wiki/Autotransformer

A rheostat dimmer was purley resistive usually wire wound.

They worked by resisting the current flowing through them thus changing the voltage dropped across them.
The resistance generated heat that's why rooms with these in were always quite warm. I think in England there are stories that lighting operators kept their dinner hot on them.

I have one here at home that was only taken out of my home-town picture theatre less then 5 years ago. It is rated for 2000W at 230V / 50Hz It may have even still being in service until then. It was one of two that controlled half the houselights each in a 600 seater picture theatre.

I also did a small show in the 1990's using a Strand Junior 8 which had 4 of these. They had switches to switch the eight channels from dim/ non-dim on and off. 

They were designed to be used by schools for drama in the 1960's.

Here's a link to the Strand archive.

http://www.strandarchive.co.uk/control/directoperated/sliderdimmers.html

Has anyone here ever worked with brine ( saltwater dimmers)?


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## Logos (Apr 21, 2008)

When I was in High School we used those slider dimmers on a production of the Scottish play. The whole thing was set up by our physics master. The lighting box was full of smoke and incredibly hot the whole time. he just sat there cackling to himself like some mad scientist. Hey he probably was.
I remember being taught to use one of the Junior 8 dimmers when I started work at out local theatre in 1964/5 as "the Saturday boy". Sweep the stage, make the tea and if someone feels like it they'll teach you something.


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## Les (Apr 21, 2008)

ah... autotransformer. That makes since. I guess the name "powerstat" misled me to believe it was a rheostat. 
Now that I think of it, this community theatre (Denton Community Theatre at the Campus Theatre) is an old renovated movie house from 1949. I think this could be what they used to control the houselights and it could have survived the renovation. It's crazy the way this building is designed. It had a huge balcony, but they put up a wall about 20 feet back from the lip and in front of it is where the tech booth is now, and above it is the front light positions as well as the followspot loft. There is still a mezzanine with a wide staircase leading to the balcony which is now a prop and costume storage area. It's quite a mess, but you can still see where the old seats were and all the half-wall partitions between levels are still there. The old speaker boxes are still hanging in the back corners (with no woofers, already checked) and the projection room (complete with fire resistant door and the sliding gates that covered the windows in case of a fire) is still up there. It now houses a large format printer and tons of old books and scripts. It's a spooky place and I'll have to take pictures. 

Safe to plug in from 20 feet away with an extension cord and GFI?

This could be used to dim down that Mole-Richardson light that I have (Just for fun).

And out of curiosity, are the copper windings seen in the back pretty dangerous when live? I'm not planning on sticking my hands back there, but I would like to know whether or not they would connect me to the power grid.


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## silvrwolf (Apr 21, 2008)

Lester said:


> And out of curiosity, are the copper windings seen in the back pretty dangerous when live? I'm not planning on sticking my hands back there, but I would like to know whether or not they would connect me to the power grid.



Ya, the backside is a shock hazard. Just stayaway from it when the unit is live. If anything you might want to consider mounting some sort of cover over that area.


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## derekleffew (Apr 21, 2008)

They are still being manufactured. Single autotransformer dimmers such as yours were generically called Variacs, just like Leko and Kleenex. Here's a link to Superior Electric, where you can still buy a similar model, albeit slightly improved. 

I worked in a "modern" theatre, built in 1986, where the houselights were motorized autotransformers, and the stage dimmers were CD-80s.


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## JD (Apr 21, 2008)

Very handy too, as the output, of course, is pure sign.

Rheostats were a funky deal. Put in series with the lamp and the load had to be balanced out if you wanted to see your lamp go very low, usually requiring "Ghost loads" in the form of additional lights in the basement or somewhere out of view. Of course, if one of the bulbs burned out, all the other lights would get brighter and you would have no low end!
As has been said by others, you have an autotransformer. One of the most reliable dimmers ever made! Outside of shock hazard, if the brushes are good, a nice piece. Don't bother rendering it for copper. For one thing, those windings are only one layer deep. The other thing is there are a LOT of collectors out there that would love it!


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## Les (Apr 21, 2008)

Cool! The knob feels nice and smooth but I did read that the brushes sometimes wear out (probably comparable to what happens in an electric drill motor). But I'll see about loading it up and plugging it in. I'll let you all know what the GFI in my garage does. I will look in to creating a ventilated cover plate for the back. My first choice of material will be a heavy gauge aluminum. I think the rest of it is ventilated pretty well!

I'll cross my fingers that the brushes are good and the windings aren't damaged!


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## Les (Apr 21, 2008)

Alright, well I plugged it in and it seems to work fine. Dims from zero to full smoothly with no jumps 

One thing I noticed before I really trust it. The windings' coatings on the back look like they were somewhat scraped off in about 2 or 3 different places. As if someone took a butter knife and lightly scraped the tops of the windings so the bare copper is exposed. It was probably bumped into. It's only on the tops, so the windings aren't touching each other but I would guess it's a bad thing that I can see bright copper in some places as apposed to the reddish brownish color of the sealant. It's not chipping or peeling, just looks scratched off. My question is, is there some type of brush on product that would fix it? It's the same thing they put on electric motor and generator armatures.

I'll probably open it up soon. Lots of dust and cobwebs making me nervous in there.
Plus I'd like to get some clamp type strain reliefs and cable and wire this up properly.


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## derekleffew (Apr 21, 2008)

Lester said:


> ...My first choice of material will be a heavy gauge aluminum. I think the rest of it is ventilated pretty well!...


I've made many gobos out of the material that surrounds your dimmer. You can probably find the exact same material at your local hardware store. Or here.


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## Les (Apr 21, 2008)

*Re: Look at this stand alone autotransformer dimmer I found*

You know, we may have some similar stuff at Lowe's! It might be a little thin, so I'll check tomorrow.


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## TimMiller (Apr 22, 2008)

*Re: Look at this stand alone autotransformer dimmer I found*

There is a place here in houston, called the houston club, its a club, but not a bar, a very high profile corprate invironment in which they hold meetings and weddings. They have a big varistat dimmer system, 0-15V control cables running all over the place to banks of varistats stacked on top of eachother throughout the entire space, lots of them up in the booth, then ton's of them back behind the room. Its rather scary when you make all the house lights dim and the varistats hum louder than anything else around.


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