The primary coil was measured with the resistors removed.All coils were measured unconnected from the rest.
Wow, didn't think that you were that invasive during your "visit", to even take things apart. But if I would have had the possibility, I would've certainly done the same.
I really think it is quite strange to wire resistors in parallel (at least at 12volts, this means a loss of 2watts, so no wonder he used bigger resistors here). This would only beware the coil from heat, if the current through the transistor is limited. But this doesn't really make sense, due to several reasons. First, you could have just fed the transistor with another base current, to get less current through the primary. Second, as the resistance of the primary is that low, compared to the resistors, still almost all the current would flow through the primary.
IMHO it only does make one sense. As I already stated before, it would be like a replacement for the freewheeling diode. But these resistors would (instead of the diode) allow quite a voltage to develop across the primary (but on the other hand they would also limit the maximum voltage, compared to nothing in parallel). So the circuit would act like a flyback. All in all, this wouldn't astonish me, if we look at how the VIC was made. But what puzzles me, is that the TIP120 can only withstand 60 volts.
If we look at how he wired the VIC, then it actually is rather a flyback circuit. Why? The secondary has only half the voltage of the 2 chokes in series. So the diode would be blocking, while the primary is on. When the primary is off, the diode would be conducting, as the 2 chokes have double the voltage than the secondary. So it would make sense, to have the primary in a flyback manner. But the TIP120 is only for 60volts, which is really not much for a primary flyback voltage (only 4 times voltage step-up would be possible, to a total of 4x5=20 step-up ratio from 12volts). And without any additional circuitry to help the TIP, it would live very dangerously (especially in a resonance condition).
Sure if you do it like that you could have higher voltages than you PIV diode rating. But only in one way. Which means, the resonating voltage in the other direction would always have to be smaller. For this, the flyback energy surge has to go somewhere. The best candidate for this: The WFC.
So it could maybe really be like this: The coils resonating, and every half wave, quite a surge is going through the circuit (when the primary is off). The good thing is, during this surge, the voltage could go as high as you like, the diode PIV isn't relevant here, as the diode is conducting. But two things would limit your maximum attainable voltage: First, the resistance of your circuit (the higher the resistance, the higher the voltage) and second, the primary transistor. If there would have been a different transistor, I would say, everything matches. But 60volts!?!
If you do not protect the transistor with an additional circuitry (like the freewheeling diode), then this simply means, that the reverse voltage on your coils is not allowed to go beyond (60-12)volts*5=240volts, which is really not much...So I'm puzzled???
All of my voltage measurements were taken at resonance.
As I said, at resonance you certainly get a completely different picture and aren't anymore only limited by the step-up ratio, but get an extension by the q-factor.
Edit:
@Don: You're sure the 57KHz is the basic resonance frequency of your coil, and not some harmonic? For actually. Under no load condition, in resonance, already with a step up of 1:10, you should get mucha higher voltage than just 10 times more. How are you driving your circuit? With a FET? Do you have the additional series diode?
