Score...again.!

[Rob Strand]

More funky stuff I'm afraid.

It occurred to me a few hours after I posted that we may not be dealing with a normal transformer at all.  Earlier on I scanned over that old manual and I seemed to remember this transformer was for the Mercury vapor lamp.  Then there's the physical split arrangement of the windings with the gap area between.

It then clicked that this transformer probably has a built-in ballast for driving the Mercury vapor lamp.

[momo]

OK I tested the thing as you suggested.

1-2: 2.5 ohms
1-3: 2.6 ohms
1-4: 2.8 ohms
1-5: 29.9 ohms.

I read up a bit about mercury ballasts.....got a headache.

:-)

Thank you for that, another experience to learn.
OK not 1:1 isolation transfo and is very old.
Seems to be able to do it's intended job.
Can I use it?
If it will just be a step up transfo with maybe ballast functions, maybe it's better I just chuck it away.
I hate doing that , it's a heavy transfo, I'm developing a fetish for heavy transfos....but I won't use wishy washy HV.
Thanks for the info and the work you put in the pictures to help out.!

[Rob Strand]

1-2: 2.5 ohms
1-3: 2.6 ohms
1-4: 2.8 ohms
1-5: 29.9 ohms.

Off hand that 2.5 ohms on pins 1 and 2 is just getting low enough for a 100VA autotransformer to make me suspicious something isn't right.  It looks like the width of the transformer is about the size of you hand grip.   A 115V 2.5 ohm winding would be OK for something that size.   However it could be a short.  You would need to check the no-load current draw.

Why the transformer is so large could be because it's an old design, or that plus the fact it's used as a ballast.

The fact the 29.9 ohm winding is sooo much larger than 2.8 ohms *really* makes me think that transformer just isn't normal.   That's going to require reading up on the design of these things.

I read up a bit about mercury ballasts.....got a headache.

Thank you for that, another experience to learn.
OK not 1:1 isolation transfo and is very old.
Seems to be able to do it's intended job.
Can I use it?
If it will just be a step up transfo with maybe ballast functions, maybe it's better I just chuck it away.
I hate doing that , it's a heavy transfo, I'm developing a fetish for heavy transfos....but I won't use wishy washy HV.
Thanks for the info and the work you put in the pictures to help out.!

I don't know all the finer points about mercury vapor lamps either.  Even though it's old technology it's not something I play with.

The ballast idea is pretty straight forward it limits the current.   In order to do that:
- the unloaded transformer voltage could be quite high and then drops to 250V with the lamp in place, or,
- the open circuit voltage of the transformer is 250V and the voltage across the lamp is less than 250V.

From the start the way these things work is there is significant voltage drop when the lamp load is used and that's not what you want for general use as a step-up transformer.   So it's not going to be a good voltage source.

In the first case, if the transformer's unloaded output voltage was very high, like 500V, it could easily blow up stuff rated at 250V.   Normal loads won't work like the lamp.

Without understanding the characteristics of that transformer it's probably not a good idea to just use it.

So I wouldn't be using it without doing a lot of reading and testing.   And up front I have doubts it can be used for a general main step-up transformer anyway.

As for having *any* use.   If you can be certain the low pin 1 to 2 resistance is OK, ie. no winding shorts, then you could use it a high voltage source.   I don't know what the open circuit voltage will be.  You would have to measure it.   Then you need to know maximum load you can put on it before the voltage drops too much.   However the fact it's not isolating means you can't power projects with it.  At the end of the day the use becomes very limited!

I found this transformer,
https://www.ballastrus.com/upload/20170904165344148.jpg

The key bit of info is it says OCV 220V, which means Open-Circuit-Voltage of 220V.   That gives some hope you open circuit voltage might not be a crazy high voltage.

[momo]

Thank much for all the info.
As I stand right now, I won't get into working that transfo.
In a box it goes for now.

OK, still looking for a 1:1 isolation "naked" transfo that I could box without the case and plugs as I can do all that.
Cheers

[PRR]

FWIW: you can't sell/buy new mercury ballasts in the US today.
https://appliance-standards.org/product/mercury-vapor-lamp-ballasts
Both because they perpetuate a poisonous technology, and because other lamp-types are more efficient.

H&M in Nevada lists a full line for mercury, but spot-checked it looks like they are all out of stock or "discontinued, call for suggestions".

[Rob Strand]

OK, still looking for a 1:1 isolation "naked" transfo that I could box without the case and plugs as I can do all that.

Unfortunately expensive.   Also depends enormously on the VA rating.  In the old tube TV days if you were lucky you could find near 1:1 ratio transformers but they topped out at 100VA to 150VA.

FWIW: you can't sell/buy new mercury ballasts in the US today.
https://appliance-standards.org/product/mercury-vapor-lamp-ballasts
Both because they perpetuate a poisonous technology, and because other lamp-types are more efficient.

Very interesting way to force stuff out.

[amptramp]

You can find isolation transformers here:

https://www.hammfg.com/electronics/transformers/line

They have 1:1 isolation and stepdown in both autotransformer and isolation versions for 240 VAC to 120 VAC which you might need if your band is touring in Europe or other places that supply 240 VAC.  These are usually rated for 50 Hz as well as 60 Hz so you can use them all over the world, but your own equipment has to be able to run on 50 Hz as well.

[momo]

You can find isolation transformers here:

https://www.hammfg.com/electronics/transformers/line

They have 1:1 isolation and stepdown in both autotransformer and isolation versions for 240 VAC to 120 VAC which you might need if your band is touring in Europe or other places that supply 240 VAC.  These are usually rated for 50 Hz as well as 60 Hz so you can use them all over the world, but your own equipment has to be able to run on 50 Hz as well.

Ron!
I see there is a Hammond office right here in town........thanks so much for that.
Will contact them today.!