Scott AW23 tweeter info needed.....

[J.N. Shetler]

I have a 7077A tweeter with an open field (for the early AW23). It should be 2500ohms. Has anyone found a source/business to rewind these? Removing the coil was easy, but rewinding would be tedious by hand. Anyone done so? Know the wire gauge and turns?

[David C. Poland]

Unless someone has the info, meanwhile, in as much as you removed the field coil:

a long shot, but maybe you can repair the old field coil:

- check that the outside lead connection to the actual winding wire is good, and re-solder connection.

- if still open, see if you can find the inside connection to the lead wire and maybe you can re-solder, or perhaps at least confirm the break is inside the field coil. maybe even dig into the coil at the inside and connect a new lead wire saving the old coil.

- perhaps unwind some of the magnet wire onto another form until you find a break to repair and see if the rest of the wire continuity is ok, and if so rewind what you removed.

If unsuccessful you might try rewinding:

- expose an end of the coil wire, burn off the coating with a match and use a micrometer to measure the wire diameter.

-find a wire gage chart with the resistance reading for that gage copper wire. and calculate the weight of the wire needed as a rough guide of the amount of magnet wire to buy for the 2500 ohm resistance target. (Compare to the weight of the old coil as well)

- absent a coil winder, search internet for other techniques. I have seen a video of someone using an electric drill  on slow speed to turn the original form with new wire feeding on to it. Stop from time to time scrape the wire to check the resistance so far, and redcoat the spot with varnish (or finger nail polish is a lacquer) and resume winding. The field coil resistance is not exacting - so a bit more or for less resistance is ok, say, give or take 100 ohms or so.

Good luck.

[John Chidgey]

I believe Alabama antique radio society rewinds field coils. They did one for me a few years back.

[J.N. Shetler]

Thanks Dave, I've done field coils before, so have already tried the "basics". There's an "open" deep within the varnished coil so not an easy fix this time. I guess I'll have to try and remove some of the potting varnish, unwind it and go from there. I figured if someone had already spec'd this coil, I could just start fresh.

I appreciate the heads up John on the AHRS. I'll reach out and see if they still offer rewind service.