Gates 250GY Iron

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Barrie:
Anyone have the specs on the Gates 250GY iron?

Several years ago I was given the plate transformer, modulation transformer, modulation reactor, swinging choke and the smoothing choke from that transmitter.

These pieces have just been sitting around, but now I have a project that I may be able to use some or all for.

Any help appreciated!

73, Barrie, W7ALW

WQ9E:
Barrie,

The Peter Dahl catalogs are still online and they are a good source for specs on this iron:  http://www.pwdahl.com/dahlcatalog/bctrans111103%5Bg%5D.html  I do have a BC-250GY and the manual so if you need additional hookup info I can find that for you.

Rodger WQ9E

Barrie:
Roger:

Thanks for the info.

I found all the specs excepting I don't understand the modulation
transformer information.  It says the primary is 7500 ohms and it says that (possibly) the secondary is 5000 ohms?

73, Barrie, W7ALW (trying to relearn AM)

WQ9E:
Barrie,

That sounds correct.  The BC-250GY uses fairly low voltage on a pair of 810's (push pull) modulating another pair of  810's in the final.  Note that the modulation transformer in the 250GY (like most broadcast rigs) requires the use of a modulation reactor and high voltage blocking capacitor so that the plate current doesn't saturate the modulation transformer.  Although this is pretty conservative iron you will still need to use the modulation reactor and blocking capacitor as in the original design.  The original Gates design uses an 813 driver for the 810 finals and a pair of 6L6's to drive the 810 modulators.

I can scan and email the original BC-250GY schematic to you in the next few days if that will be helpful.

73, Rodger WQ9E

Barrie:
Roger:

Thanks again.

Yes, I'm well aware of the use of a modulation reactor, or at least I was 15 years ago.  I built a transmitter at that time using a push-pull pair of 450TLs, modulated by a pair of 304TLs (AB1), using a modulation reactor.

I plan on rebuilding that transmitter.

However, the rig I'd like to build right now is a push-pull pair of VT-127As (similar to the 100TL), modulated by a pair of the same tubes (again, if I can, AB1).  I don't know how well that modulation transformer would match-up in that situation.

I guess age must be creeping up.  I have trouble remembering things I once knew.  I've been hitting the books, but there is very little information in the books about AB1 modulation.  And, I don't have the curves for the VT-127As, so I can't calculate easily.

73, Barrie, W7ALW (vanity call, but also my original call from 1950)

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