Thanks very much for the copper confirmation Gary. There seem to be several manufacturers of ST heads and quality is not the same from them all, as others have reported in the past. I'd only recommend DES as a source for them now.
Someone recently mentioned having high resistance connections at the field coil interconnects- if you find crimp tubes, I'd suspect aluminum. They look like they have solder, which they may, but those tubes were used on Jeff's aluminum head so be warned. Both the copper units I have just twisted and soldered field coil interconnects. It's easy to find an accessible wire and carefully scrape off a tiny spot of the red insulation. Then touch up with red electrical varnish or fingernail varnish.
We put together my backup ST-3 generator head (rotor and stator) yesterday. It was purchased about 15 years ago and rotor and stator were shipped separately to allow UPS delivery. Alas, upon inspection of the stator housing casting, we found a crack that ran almost full length near one foot that had been puttied and painted over. I bent and cut some angle iron to fit, and JB welded and bolted it in place. to re-secure the case. Put it all together, hooked up power and a horrible noise is made...the rotor is rubbing on the stator when powered. Visible scratching on rotor and stator. We find that the stator laminate assembly is loose in the case. Drove it back in place, tight, and put it all back together and it still screams when powered. Eventually had to take out the rotor, chuck it in my wood lathe, and true the rotor with an angle grinder while spinning the rotor. Quite a project but it came out very nice. I also smoothed the stator laminates with a 3" drum sander in a drill. After shimming the end bell to center the rotor within the bore, I now have 0.017 inches clearance all the way around (tested via tape strip on rotor). No more binding under power but and then find the harmonic output is pathetic; I can't get over 170 volts with no load though can get 230V on a 12V battery for excitement. I finally tried the 240V AVR I got from china for $25 using the 240V output as harmonic input. That works well and now Jeff is finally back with power again. I'm not very happy with my backup head as my current homebrew AVR requires the harmonic for startup. I'm now very happy to have gotten lucky on my 1st ST-3 which had only the usual and expected bearing and diode bridge failures almost immediately.
Tom at CGG is using Jeff's dead head end bell casting to restore a broken returned unit for Jeff's replacement. Good of him to make good on this troubled unit Jeff had.
It's history:
1 Broken end bell casting which I repaired via steel/bolts and JB Weld.
2 Broken foot casting broke due to uneven casting/machining, repaired by steel/bolts and JB Weld, reground all feet to flat on bottom.
3 "New improved'' bearings failed (groaning) in less than 10 hours of run time.
4 CGG supplied AVR failed in about 30 hours.
5 Field coil failed open at perhaps 60 hrs of run time, eventually found to be wound with 19 gauge aluminum instead of copper so rewinding expense and time utterly wasted.
6 Harmonic output no longer adequate after field coil failure, even with rotor replacement (loaner rotor from my backup unit). It can't handle more than a 1500 watt load.
I do wish there was a smaller Stamford style head available, as I'm getting fed up with ST troubles. I'm going to be kinder and more grateful to my older ST-3 which has been quite reliable. Knock on wood.