Thhordarson T-45745 Secondary test volts?

[N0WEK]

I've got a couple of Thordarson T-45745 5vct/20amp transformers, but I can't find them listed anywhere. I've checked the Bunker of Doom and can't find it listed. I need to find out what the secondary test voltage is.

Anybody got some info on these?

Thanks,

Greg

[Opcom]

That's a lot of digits. Could it be T-4574S or something?

[N0WEK]

That's a lot of digits. Could it be T-4574S or something?

Nope, just looked again and that's what it is... T-45745.
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Greg

[W7TFO]

That type of number on a Thord means it was made as an OEM job.  Prolly won't be in a published guide.

73DG

[KA2DZT]

All 5 digit part numbers are specials, like Dennis said, made for an OEM.  The xfmr is either one of two things, made for high voltage rectifiers or just for regular 5 volt filament tubes.

Look at the 5 volt terminals. What do you see??  Big insulators, then probably for high voltage rectifiers.

Fred

[N0WEK]

All 5 digit part numbers are specials, like Dennis said, made for an OEM.  The xfmr is either one of two things, made for high voltage rectifiers or just for regular 5 volt filament tubes.

Look at the 5 volt terminals. What do you see??  Big insulators, then probably for high voltage rectifiers.

Fred

It's got pretty good size ceramic insulators (half inch tall or so) for the secondary. I notice that Thordarson had similar transformers with 2,500 volt and 10,000 volt test secondaries. I guess I can figure that it's at least 2,500 volts.

Thanks,

Greg

[KE6DF]

Another way to guestimate the specs is to measure the inductance (with your DVM Henry scale) and measure the DC resistance and the weight.

Then look for similar catalog entries.

If the inductance is > 15 hy or so, then probably it's a swinger.

[N0WEK]

Another way to guestimate the specs is to measure the inductance (with your DVM Henry scale) and measure the DC resistance and the weight.

Then look for similar catalog entries.

If the inductance is > 15 hy or so, then probably it's a swinger.

Sounds like a good plan if they were chokes, in this case they're 5v filament transformers. They've got plenty of iron and copper in them and I have all the ratings except for the test voltage.

[W7TFO]

Got a megger?

A good idea on any vintage iron before it goes back to work.......

73DG

[N0WEK]

Got a megger?

A good idea on any vintage iron before it goes back to work.......

73DG

That I do, one of the nice old crank types in the leather case. I'll have to give them a good warm up for awhile and then megger them.

Thanks

Greg

[KE6DF]

Another way to guestimate the specs is to measure the inductance (with your DVM Henry scale) and measure the DC resistance and the weight.

Then look for similar catalog entries.

If the inductance is > 15 hy or so, then probably it's a swinger.

Sounds like a good plan if they were chokes, in this case they're 5v filament transformers. They've got plenty of iron and copper in them and I have all the ratings except for the test voltage.

Well that will "learn" me not to read the posts more carefully. :-)

Still, what I said can work to some extent.

A 5V 20a transformer would likely be for one of two things. Either it was intended to power large 5V transmitting tubes like 4-250, 4-400 or it was intended to power a couple MV recitifier tubes.

20a is an unusual current for power 5V transmitting tubes as it's too much current for one tube, and not enough for two.

On the other  hand, it's just right for powering two 575A or 673 rectifiers and in that case, it would have a high voltage rating.

You can probably tell a lot from the weight as a rectifier transformer with a 10KV rating is significantly heavier than a typical transformer made to power transmitting tetrodes.

[W7TFO]

Fils for two 806's = 5V @ 20A.

Hmmmm...

73DG

[KE6DF]

Well 806's are a possiblity, but that's a rare tube.

Anyway, I found two 5V 20a transformers in my stash.

Both with 10KV ratings for powering rectifiers.

One weighs 9 lbs (UTC S Series) and the other 15 lbs (Chicago).

The bigger one is a mill spec brute.

Checking an old Thordarson Catalog (the 1949 version) shows that most of their filament transformers have a 1600V RMS rating -- except for the ones intended for rectifiers.

A thordarson 5v 21A 1600VRMS unit weighs 5 1/4 lbs (T21F07)

Dave

[W2VW]

Only one secondary?
Some full wave bridge fil xfmrs have three sec. windings.

[W7TFO]

Well 806's are a possiblity, but that's a rare tube.

They weren't rare when those transformers were made...

Also, S-series UTC stuff was the cheapest, hambone stuff on the market.  All were ICAS rated, so NEVER depend on any of them to hold up under buzzard conditions.

From a guy that has zorched enough of them to know!

73DG

[KA2DZT]

Well 806's are a possiblity, but that's a rare tube.

They weren't rare when those transformers were made...

Also, S-series UTC stuff was the cheapest, hambone stuff on the market.  All were ICAS rated, so NEVER depend on any of them to hold up under buzzard conditions.

From a guy that has zorched enough of them to know!

73DG

I agree,  S series chokes are some of the poorest performers.

Fred

[N0WEK]

These look like mil-spec brutes! They weight a little over 14 lbs each and one of them is painted that light blue I've seen on Navy stuff.

Thanks for the help guys!

Greg

[The Slab Bacon]

Keep in mind that if they are MIL spec transformers, some of them had fairly tall porcelain insulators even though they weren't high voltage rated. I have a few like that. I have one large one that is potted with 1/2" tall porcelain insulated terminals and it is only 30v @ a lot of amps with a gillion taps.

Sounds like a HI-POT test is in order if you plan to use them as rectifier fil transformers.