WTB: Push/Pull Plate-to-Line Transformer.

[jazzcrisis]

Looking for a 30k:600, 20k:600, 15k:600 or similar line output transformer with center tap that can handle a few ma of DC in the primary.

Application is for a Langevin AM5116-B clone, and the poor Edcor I was using to test couldn't handle the current (even though I've had success with those in the past in similar circuits--imbalance was only 2ma.)

 

[shabtek]

Did the coil burn open

 

[jazzcrisis]

Did the coil burn open

No. It still measures fine, but when passing audio through the transformer and viewing on a scope, one side of the secondary is about 1/3rd less gain. Turns out I mis-wired a rotary switch for selecting my feedback resistors to change gain, so the push side was seeing 150k while the pull side was seeing 100k. The problem persists even after correcting that, so I'm not sure how the TX was actually damaged. No shorts or opens, DCR measures as normal.

 

[scott2000]

rackmonkey had some $weet Chicago opts a little bit ago....

https://groupdiy.com/index.php?topic=76069.0

 

[shabtek]

magnetized core? run large low hz signal through heavily loaded
measurement error? try flipping connections

 

[emrr]

The PM660 uses those and runs a good but more current.  I’m skeptical you caused a problem, sometimes Edcor sends junk. 

 

[rackmonkey]

As Scott mentioned, I have some Chicago BO-10’s. Remind me, is the 5116B AC coupled? If so, these are worth thinking about. But if you’re looking for Edcor-ish prices, these aren’t the droids you’re looking for.

 

[rackmonkey]

I also have several pairs of very nice, vintage UTC, Thordarson and ADC 30k-600 PP units from old RCA, Collins, GE, and Gates equipment. If you decide you want to spend more for more period-correctness, there are options. I’m sure others here would have some choices along those lines as well.

Which Edcor model were you using? XSM?

 

[jazzcrisis]

I also have several pairs of very nice, vintage UTC, Thordarson and ADC 30k-600 PP units from old RCA, Collins, GE, and Gates equipment. If you decide you want to spend more for more period-correctness, there are options. I’m sure others here would have some choices along those lines as well.

Which Edcor model were you using? XSM?

5116b's are DC coupled, B+ to the center tap. I'd say my budget is <$100, but will keep those in mind for whatever the next build is!

 

[jazzcrisis]

The PM660 uses those and runs a good but more current.  I’m skeptical you caused a problem, sometimes Edcor sends junk.

I think you're right. I have since determined that if I ground the secondary center tap, I do get symmetrical waveforms on each half of the secondary and everything seems OK. Strangely, if I leave it floating, one side is way down. Low freq. response is terrible so I think the transformer might be magnetized or the core is saturating, as mentioned above.

 

[shabtek]

i suspect it does not sound how it looks