Edcor Transformer Problems

[Astera]

I'm not trying to be obnoxious toward Edcor, more of a heads-up in case someone runs into this in the future!

To be brief, the output transformers I ordered from Edcor are wired or wound incorrectly.

I had ordered four output transformers from them a few months ago and they were excellent — no problems. I have them running in a pair of PCB-based Darlings. Edcor make an excellent transformer at a good price for the hobbyists like us.

I ordered another four recently however and they're going to have to go back. The first clue was when I wired up my third Darling and the volume coming out of the speakers was exceptionally low. After much tube and PCB swapping I finally isolated the problem to the transformers. Somehow they're not to the same spec as the ones I ordered earlier.

I'm unaware of a test to determine how the transformers are incorrect. A simple resistance check across the input windings showed only a 1% difference between the good and the bad transformers.

Anyway, just a heads up to check the transformers in circuit if you can before you cut the leads or paint the bells (as I did).

 

[TheGimp]

You can check the turns ratio by driving one winding with a signal generator and measuring the output on the other winding.

 

[tomchr]

Painted bells or not, I'd verify that the transformers are indeed wound incorrectly, then present Edcor with the data. See what they say. It doesn't cost much to send an email or make a (non-confrontational) phone call.

~Tom