Michael Black wrote:
Scott Dorsey ) writes:
Primary 20,000 ohms single plate 10MA DC
Secondary 500 ohms

Ahh, wait, you DID give impedances!

What you want is a 20K to 600 ohm line output transformer. I bet a nickel
Hammond makes one.

There was a time when everyone made them. If you were making a phasing
rig, you'd need those to interface with the B&W phasing network (the
ones that came in a package like a metal tube). The B&W seemed to
be the most common, but I think the other similar networks (Central
Electronics was another manufacturer) used the same sorts of transformers.

You saw transformers like this in most audio equipment... you'd see a
single-ended output stage, often a 6AQ5 or even a 6V6, driving an output
transformer for a 600 ohm output. This was one of the most common
transformer types around because everyone used them for their output
stages.

But you're right... Hammond doesn't have anything in the catalogue,
although they do have a 20k to 32ohm output transformer.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Gene Marcus wrote:
Thanks for the tip Ed, but I have used T-201 to replace T-204 in the
past. T-202 is bad. When all is said and done, I will probably have to
use the two good original transformers as a matched pair in the output
circuit (T-202 and T-203) to maintain balance.

Sowter 9915. Freaking expensive but it's what you want.
http://homepages.tcp.co.uk/~sowter/a...FORMERS_5.html

I am really, really surprised Hammond doesn't still make one.

I don't know why the audio transformers seem to be the weak link in
this rig. The B+ is correct and I'm measuring 4 ma through the
high Z winding, well below the rated 10 ma.

Probably because they got the cheapest possible transformers from a low
bidder, since they were commodity items. And they have a huge number of
turns of tiny wire in the primary, so it doesn't take much to damage one.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:



Sowter 9915. Freaking expensive but it's what you want.
http://homepages.tcp.co.uk/~sowter/a...FORMERS_5.html


Wow, your not kidding. I think this project will be on hold until I can
either find a replacement or a junk donor rig at a hamfest.

Thanks for all the info Scott.

Gene

Gene Marcus wrote:

Wow, your not kidding. I think this project will be on hold until I can
either find a replacement or a junk donor rig at a hamfest.

Whenever you go to hamfests, ALWAYS go through transformer boxes. Anything
you see for a couple bucks, buy it. Sooner or later you'll need them all.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."