I have less experience with the Chinese stuff, but have long worked with the (once) American made Marathon heads and others. We have had quite a number of them repaired and rewound over the years, usually by specialty winding shops with all the tricks/tools/and expertise. The LIMA MAC variety is one that is brushless and "inherently regulated"... does not require anything other than its own residual magnetism and very precise winding specs to maintain its voltage within 5% under almost all conditions including minor overloads. We have seen occasional rewind failures due to off-spec wire where the output voltages would be off significantly with only a slight, almost imperceptible, change in the wiring used. We have also seen struggles with some of the Italian heads which apparently used a metric wire size and correct outputs could not be achieved nor properly maintained when rewound with conventional North American available wiring stocks. This is from work done by well seasoned winding professionals who were quite well versed with all the technicalities and nuances.
More recently we have received a large quantity of Chinese ST heads specified, marked, (and supposedly pre-tested) for 60Hz 120/240 operation. Unregulated these heads are producing closer to 300vac at 1800rpm. Tom at CGG confirms that many of his do exactly the same thing out of the box and need a regulator or rheostat to bring them into spec. This may just be the norm with the ST variety of Chinese heads in current production.
With the reported under-voltage stuff and our recent experiences with the ST overvoltage, I am led to believe that manufacturing expertise and conformance to precise specifications may be quite lacking in much of the Chinese stuff. This may have nothing at all to do with the one noted case of sub-standard aluminum windings but rather be more to do with loose or variable manufacturing tolerances. Sound familiar? Like something out of Rajkot? I think it is the same syndrome of immediate money vs quality control - very shortsighted and foolish in my own worldview.
dieselgman