Mod Transformer Substitute

[flintstone mop]

Hello my Friends,
I need to pick some brains. Before I post a Want Ad on the Forum.

I am trying to find a substitute modulation transformer for my Elmac AF-67. A pair of 6L6 or 5881 mod tubes and the final is a 6146. The manual indicates a 5000 ohm secondary. I'm not sure what the load for the mod toobs is.
 
I would hate to shell out $75 for a used-but-good unit.

The Ranger mod transfrmr looks interesting but, I don't know what the load for the mod toobs is. The Ranger uses 1614's modulators and, of course, the final is a 6146.

The Tim-of-Tron told someone on the board that a TCS-12 mod transfrmr might work in the Af-67 but, that Tx uses a pair of 1625 mod toobs and the final is a pair of 1625's.
Thanks for any help.

Fred

[WBear2GCR]

You can probably figure it out by working it in reverse:

- you know the Bs+ for the finals
- you know the secondary impedance
- you know the primary Bp+
- now you need to know the primary impedance

To make 100% modulation the rig will need to produce 2x Bs+ *peak* AC swing from the modulator tubes. So, depending on the drive (AB2 or AB1) we can make some sort of determination as to how much swing the mod tubes can make... but we can assume to start that they make full swing to the Bp+ rails...

Now we know the turns ratio of the transformer! It's the voltage ratio.

Plug that into the equation for impedance vs. turns ratio, and since we know the secondary's impedance we can quickly determine what the primary is going to be in ohms! 

Just look out for the PP primary and single secondary when spec'ing it...

             _-_-WBear2GCR

 

[flintstone mop]

Thanks Bear,
Getting back to the basics. I'll figger this out. It's easy math.

Fred

[KB2WIG]

there is always home rewinding.....