Collins 26U-1 Interstage transformer.

Hi Group:
I've got all the parts to build a pair of Collins 26U-1 limiters except for the interstage transformer. The spec's are 30K to 68K. This makes it a 1.5:1. Anybody know of a good substitute for this one? I could build the 356E-1 and not need an interstage but I think I want to go for the 26U-1.
Any Ideas?

RonL

A 30K:68K interstage with full audio bandwidth is a tall order. But Edcor might be able to wind something for you. And keep an eye on evilBay, of course...

Look on evilbay, there are some UTC's right now that might work.
we need schematic to analyze dc.

I'm not having much luck finding a substute. I think I'll build up the input stage for the 26U with a 6386 and do some testing. Judging by the size of the original it needs to be pretty hefty. I'm almost thinking about winding this one myself.

Hi guys, have a chat with Brian Sowter he does custom stuff and is very helpful, helped me no end with my BA6A tranformers.

Cheers Gary O.

[quote author="rlaury"] interstage transformer. The spec's are 30K to 68K. This makes it a 1.5:1. [/quote]

I'm sure this isn't new info to you, but just in case: UTC HA-137. I would expect to pay a small fortune for them on eelBay, since anything UTC with the "HA" prefix is coveted these days.

Looks like LS-25 would work too, buy same scenario with regards to cost/availability.

CJ's wonderful UTC page.

I just saw you original post asking about the 26U, and its really awesome that you got those original output tranformers. I couldn't find a schematic for the 26U. I'm collecting parts for a 356E clone.

Almost all of your innerstage transformers are about the same ratio, 1:1.5, 1:1.7. This means tou have a lot of transformers to choose from

What was the original?

The UTC CG series, the round can models, might be the way.
Post a circuit so we can see how much dc is going thru the windings.

Manual:
PDF

No unbalanced DC in the primary.

Right.
HA-137. Like the post before me says.

I have seen those on evilbay once in a while for cheap.

Since no dc, and only 100 mw, you should be able to use any innerstage you want.

Interstage from BA6A could that work ?

WOW! The HA-137 thats it!
The Collins manual says it's mfg by UTC
but doesn't give the model number.

Thanks guy's!

Do I get a prize? :wink:

I've been thinking about this for the 356E clone, and was wonder if I could get away with a smaller transformer, like the A-18. The 356E used a 600:60k originally, but is that kind of step up necessary?

I was going to eliminate a transformer, and use either 12AV7 or 6SN7 plate -> A-18 -> 6386(or 6BA6) grids. The A-18 only handles +18dbm. Poop.

Edited to explain the idea better. Who am I kidding, no one cares about my hair brain schemes. :green:

Nope, But I'll have a beer tonight for DIY in your name.
Really though, thanks a lot. Ive looked through the UTC catalog I had
but the interstage page was missing.

RonL

[quote author="rlaury"]Nope, But I'll have a beer tonight for DIY in your name.[/quote]

That's all I could ask for. :sam: I'm looking forward to seeing how your project turns out. Thanks for sharing. :thumb: