Variac car boot find, Can anyone identify?

[ajgriff]

Reversing the dial only reverses the scale. You can't gain voltage at one end of the winding by losing it at the other. Have a look at Figure 4 in the article referred in Post #28 as the wiring diagram for a Variac is shown there. This might also help to explain my previous comments about current capability and the over-voltage tap.

I'd be surprised if the original brush were round and the size of a pencil lead. It still looks to me like a Zenith/Lyons Variac which probably would have had a thin flat rectangular brush fitted into a slot in the spring loaded brush holder. If so the brush referred to in Post #24 can easily be adapted to fit.

By the way, are there any markings on the paxolin terminal plate as mentioned in Post #41?

Alan

[barrymagrec]

If that Variac is like the one my Dad had from about 1961 the brush assembly is a small brass arrangement threaded at the back and with a small round carbon brush sticking out at the business end. The carbon brush breaks off quite easily - we had a spare or two but I have no idea where they would be now.

The winding tappings are brought out of the stack with a mica insulator, it should be quite easy to work out which end is which.

[ajgriff]

Looking at the second photo in Post #21 the track of the old carbon brush is clearly visible and it doesn't look like a track created by a small round brush the sze of a pencil lead, not to me anyway. I may be mistaken of course.

It's the 'mica insulator' that should be marked with the model designation. Also, it should be simple enough to establish connectivity of the winding using a meter set to continuity or resistance ranges.

Alan

[Bomber county]

Originally Posted by ajgriff

Reversing the dial only reverses the scale. You can't gain voltage at one end of the winding by losing it at the other. Have a look at Figure 4 in the article referred in Post #28 as the wiring diagram for a Variac is shown there. This might also help to explain my previous comments about current capability and the over-voltage tap.

I'd be surprised if the original brush were round and the size of a pencil lead. It still looks to me like a Zenith/Lyons Variac which probably would have had a thin flat rectangular brush fitted into a slot in the spring loaded brush holder. If so the brush referred to in Post #24 can easily be adapted to fit.

By the way, are there any markings on the paxolin terminal plate as mentioned in Post #41?

Alan

It was missing the cover plate when I picked it up unfortunately, there are no markings anywhere (other than on the dial).
The brush holder looks to be original but rather under engineered. I would be interested to see the brush arrangement on another one if anyone has one. I have something in mind which could be adapted fairly easily and plenty of spare brushes to fit it if need be.

[MotorBikeLes]

I think I mentioned this in a much earlier reply. Most variacs I have seen have four connections plus the output.One at the bottom, one about 10% up, one at the top and finally one at 10% down from top. Depending which way you have the scale and how you drive it (the control wheel) you will typically have mains neutral at the bottom, and the live at the 10% down. This then gives an output of 0% to 110% of the mains input voltage. I have used these for motorised control of lab kilns years ago.
Les.

[ajgriff]

Originally Posted by Bomber county

It was missing the cover plate when I picked it up unfortunately, there are no markings anywhere (other than on the dial).

The markings I'm referring to were not on the cover plate. They would be on the paxolin plate holding the wiring tags which can be seen in your very first picture. If there are any, they could be obscured by dirt as they are quite faint impressions. Worth careful inspection.

I could photograph the brush on mine but I confess that I'm loathe to dismantle it as I've only recently put it back together!

Alan

[Bomber county]

Ahh ok. I'll have another look when I next have the cover off next week then. Stiil got to add a fuse and a meter to it before I can call it properly finished.

[ajgriff]

The attached images show what a typical early Zenith Variac brush assembly looks like when removed from the armature. By the way, I found these quite quickly by 'googling'.

Alan

[Bomber county]

Originally Posted by ajgriff

The attached images show what a typical early Zenith Variac brush assembly looks like when removed from the armature. By the way, I found these quite quickly by 'googling'.

Different to mine, its more or less a shouldered brass threaded bolt with a hole in one end for the carbon. There is no coil spring in it as the wiper arm itself seems to be made from spring steel. My earlier photo might be a bit misleading, as it had been used in the past with the brush worn down to nothing (brass on copper) the wear track looks quite wide.
I had a more modern one a few years ago with a rectangular sprung bush and a solid arm(sadly it was a 120v US one off one of the American bases so not much use).

[ajgriff]

Sounds more like the one described by 'barrymagrec' in Post #44. I'd be interested to see a photo if you get the chance.

Don't think there's much more I can offer with regard to your Variac but I do hope you find it a useful addition to your armoury and well done for saving it!

Alan

[Mr Moose]

Hello,
I have three variacs that appear to be similar to yours.
The most similar is shown in the first picture and is a Zenith Type 587CMHs.
In the second picture is a Zenith Type 200CMH. It is the same size as the 587CMHs and only seems to differ in having round holes rather than slots for ventilation and a hole in the flat brush spring for the brush to go through rather than a half moon cutout as in the 587CMHs.
The third picture is from a Claude Lyons catalogue and shows their Type 200CMH variac which appears to be identical to the Zenith 200CMH.
The Claude Lyons 200CMH is rated at 230V, 580VA (possibly explaining the 587 designation), 2A (possibly explaining the 200 designation).
(You can take 2.5A at output voltages between 0 and 60 volts or between 170 and 230 volts but it drops to 2A at 115 volts and at 270 volts.)
The fourth picture shows the brush from my third variac which is an uncased 200CMH (You can see the round hole for the brush rather than the half moon cutout of the 587CMHs)
The last picture shows the brush in its brass holder.
According to the Claude Lyons catalogue the reason for the brush being in a brass holder is that when the carbon brush wears away the larger brass holder will short circuit a turn and blow the fuse!
Your variac has the switch and terminals normally fitted to the bench mounted variac which has the mounting plate at the bottom so at some point it may have been converted to panel mounting with the mounting plate at the top.
Yours, Richard

[ajgriff]

Really interesting post Richard, thank you. Has allowed me to stop scratching my head.

Alan

[ajgriff]

This page from the now defunct Claude Lyons website refers to some of the Zenith Variacs mentioned in this thread and gives some further background to the introduction of Variacs to the UK:

https://www.claudelyons.co.uk/index....ges&Itemid=267

Alan