Input transformers

[Detroit47]

I came upon a box of transformers in my travels. Some of which I have no data on. I have  Three McMartin MT-4 transformers the also say 2-A-78  23045 on the side. And several Newcomb  TR-91  input transformers no data except pri 50/200 ohms sec to grid. There is also a couple of small potted ones  labeled MT23  AG. They were all in a box marked audio transformers. Any data would be great .

Thanks John N8QPC

[KA2DZT]

The 50/200 probably has two input windings.  In series you get 200 ohms, in parallel you get 50 ohms.
Then your high impedance secondary winding which you connect to your grid, other end grounded.

Fred

[Opcom]

The one or two of those house brand units I have had open makes me believe they were made under contract by one of the larger manufacturers. A McMartin one looked very much like an Altec one. It doesn't matter so much as those should be quality USA made stuff, use them in good health! 

[Detroit47]

I am going to take pictures of them. I have some other ones with no markings on them. They look like balanced to unballanced input transformers that i have seen before.

John

[KE6DF]

Someone listed a McMartin MT-4 on ebay.

They included the following pin out data:

"The MT-4 parameters are: Pri: 1-4: 600R, 1-3: 50R; Sec: 3-8: 10K, 2-8: 60K"


http://www.ebay.com/itm/VINTAGE-MCMARTIN-MT-4-MICROPHONE-AUDIO-INPUT-TRANSFORMER-/251109747531?pt=Vintage_Electronics_R2&hash=item3a774eab4b