help ID Collins transformer

[Opcom]

I have a nice transfomer, looks like a filament one. Could be really nice for a classic project using 866's.

Collins 672-0370-00? (paint mostly gone)
UTC E-7506
size, about 4" cylinder, 6" tall, square flange on bottom, with recessed terminals designed for a circular cut-out in the chassis. The 3500V insul. fil. winding has two nice little ceramic cone insulators.

1-2-3-4  120/240V  1500V insul.

5-6-7? unknown winding  -anyone know this one's Voltage, possible CT, and working volts please?

8-9  2.5V  10A  3500V insul.
10-11  2.5V  10A  2200V insul.
12-13  2.5V  6.5A  1500V insul.

I also wonder what it is from?

Thanks for any help!

[WBear2GCR]

Ummm... plug it in and see what the voltages are on 5-6-7??

The rating would be based on whatever resistance caused a 10% drop in voltage, for CCS rating. (iirc)

[Opcom]

I could do that, but I'd prefer the data if it is available, and I think the true reading would only be found by loading the known secondaries fully then loading the unknown one for the 10%.

I believe it is military, as there's an NSN and those special brokers offering it. However they likely know not what it is for. Been down that road with them, they are sales companies with unfortunately little technical interests, for the most part.

It' beauty for me is that it's probably 6.3VCT, but how many amps - that's key. Could it take a pair of 811's? or is it for something else like 4X250B's, at 6.0VAC? so there's the important issue as to what it was used for.

[w4bfs]

Ummm... plug it in and see what the voltages are on 5-6-7??

The rating would be based on whatever resistance caused a 10% drop in voltage, for CCS rating. (iirc)

thats interesting, Bear and Pat .... I'm assuming you are finding open ckt voltages and then loading with decreasing resistance until you see 10% V drop ... This is the first time I have heard of this method and am curious where you came up with it ... I think you would need also to fully load the other windings on a multiple output xfmr to avoid overloading the xfmr in the first place ...73 ...John

[Opcom]

It's an 'old saw' type of rule or technique based on the supposition that a decently made transformer drops its volts by 10% on a secondary at full load. I believe in loading all secondaries to make it meaningful considering the total primary VA rating.