Standel driver transformer replacement help.

[R.G.]

Yeah - I wasn't *really* going to type all that in again.

If anyone was really interested, I'd have dug that out and pointed to it, but you've saved me the trouble.

The funny thing about all this is that designing a driver transformer that works OK is not too tough as long as you don't need to pare every last cent out of it. Using a donor that's too big will produce something that works fine. Thomas and the other companies could not do that and still make a profit, so they were all designed to be as cheap as possible - but no cheaper.

It's very strange what affects the design. What changed the number of turns on the secondary most was the emitter resistor values and the values of the bias network resistors as well as the driver secondary windings themselves. This was a far bigger voltage to overcome than the base-emitter junction itself, and therefore affected the driver design more.

Anyway, since that write up, I've done a much more thorough write-up on the re-creation, along with diagrams and commentary, all ready to go... as soon as I can break free enough time to actually do the winding on the donor and test the results.

[R.G.]

*very* early draft of where I'm going with the driver transformer stuff

[gbono]

So is the the interstage transformers damaged? If the Standel design can use the same transformer that was used in the ACC 150 power amp design, one can find these amps on feePay. The guitar center reissue of this brand has taken a big bite out of the resale of the 150/140/etc. series.

BTW Metheny used an ACC 134 for 20 years......

[J M Fahey]

FWIW hereīs a working link for the Delco amp.
Mind you, itīs designed for Germanium transistors, so some tweaking should be needed for Silicon:
http://www.updatemydynaco.com/Histor...lco100Watt.pdf

[Anthony]

I'll have to pull the driver transformer for further testing. Between my Arduino winder project and archtop build, It'll probably sit for a while. I really appreciate all the input.

[R.G.]

Good idea. If you pull it, you can apply the open circuit tests and know if it's that transformer or not.

If the transformer is dead, you have a chance to become the world's foremost expert on Standell driver transformers by documenting it as you disassemble it. Lamination size, spacer thickness (it's almost certainly gapped, not interleaved) and both number of turns per winding and winding order give you a how-to-replicate recipe for it.

My difficulty with Vox transformers is largely that I've never had one of mine die. If I had, I'd already know how to make one without doing sneaky measurements on it. As it is, I think I have it down, so as soon as I can get to that winder...