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PostPosted: Wed Feb 24, 2010 9:13 pm 
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Hi.

Just wondering if anyone can identify this ballast I found in the skip at a Depot visit today?


http://i64.servimg.com/u/f64/13/34/36/73/24022010.jpg

http://i64.servimg.com/u/f64/13/34/36/73/24022011.jpg


It's big, heavy, black and has nothing on it to identify what it runs or who made it.


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PostPosted: Wed Feb 24, 2010 9:31 pm 
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Given the age and size it will almost certainly be a leak transformer for 140W SOH/90W SOX. The number of terminals means it will be a multi tapped type with various voltage tappings. There will be 2 lamp connections and 2 supply connections but with 8 terminals it will be near enough impossible to work out the arrangement. I have some similar 8 terminal ballasts but there was no standard convention for labelling them.

Are all the markings definetly gone, have you examined the top under a very bright light when looking at it at an acute angle?

GEC ballasts tend to have the lamp connected across 1 and 8 or 1 and 7. If 1 and 8, capacitor will be across 2 and 7, or 2 and 6 if the lamp is 1 and 7

Then for supply which usually has 10v tappings it may be 3/5 or 4/6.

Sodium lamps are tolerant of overload for short periods and that ballast is chunky enough to withstand abuse.

Check there is high impedance (M Ohms at least) between all the terminals and earth.

Then I would try, lamp 1 and 8, cap 2 and 6, supply 3 and 5. Fit a 3a plug fuse and see what happens. If it lights, time how quickly before the lamp starts to go yellow. Then compare that with a cold lamp on known good 90w gear. If it is quicker the voltage tappings are slightly out, if a bit slow, I'd leave it as the lamp will be slightly under run which will preserve it and the ballast.

Can you not ask at the depot if they know if it is mercury or sodium gear?


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PostPosted: Wed Feb 24, 2010 9:48 pm 
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It looks 1950s GEC to me, possibly an old mercury choke.


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PostPosted: Wed Feb 24, 2010 10:04 pm 
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Thanks for the replies.

There's no hint of any writing on it at all. Just a fancy paint finish.

If it helps, 1, 2,5 & 7 look the most likely to have been turned recently. However, upon shaking it, the ballast has a rattle. I suspect the internal insulation is breaking up.


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PostPosted: Wed Feb 24, 2010 10:09 pm 
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Yep if you can see marks on the screws or bits of wire left in the terminals that helps. In that case I would say lamp 1 and 7, supply 2 and 5, with capacitor across the supply. I wouldn't worry about the rattle, could be a lump of rust or some tar/pitch insulation which has come off inside. If the earth test is OK, I would try it with a lamp. Unless Mazeteam knows of any large mercury installations around that area, the chances are it probably is sodium rather than mercury. I would have thought all large mercury gear would have long gone from the depot.


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PostPosted: Wed Feb 24, 2010 10:21 pm 
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That was interesting...

I just connected power to terminals 2 and 5, multimeter to 1 and 7. Gave 362v. Connecting meter to 1 and 6 gives 110v.


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PostPosted: Wed Feb 24, 2010 10:35 pm 
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Careful powering any lamps just yet, in case it does turn out to be a mercury choke rather than a sodium leak-transformer.

I have some old early-60s 400 watt GEC mercury chokes that have eight terminals each. The first four terminals are input taps, the last four are output taps, and only one of each should be connected, offering a total of 16 different combinations. A series of indicated voltages are printed on its label, allowing use on a supply from 185 to 260v AC in 5 volt increments. Like so (please excuse the bad mobile phone picture):

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Not sure what sort of readings this would give, but I can check one if necessary.


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PostPosted: Wed Feb 24, 2010 11:52 pm 
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Phosco152 wrote:
Unless Mazeteam knows of any large mercury installations around that area, the chances are it probably is sodium rather than mercury. I would have thought all large mercury gear would have long gone from the depot.

That's the quandry... As in recent weeks, there has been a rather large ungeared round floodlight at the depot. It's the sort of thing that would be mounted on a wall and light either a church, or possibly the front of The Minster. This time at the depot, that light was in the skip, and so was this rather large box ballast. The ballast was at the other end of the skip to the floodlight, but the ballast/transformer is way too big to fit into a column

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PostPosted: Wed Feb 24, 2010 11:54 pm 
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I wonder if it is a 1000/2000w ballast?


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PostPosted: Thu Feb 25, 2010 1:08 am 
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The only way of knowing is to find an identical installation...

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