Quote from: NickZ on August 03, 2017, 11:25:11 PM
   
I'll test the new yoke without the snubbers on, first, cause my FETs are junk, anyway. According to Hoppy, And they might all be bad, but there might be a couple fets that will work, for now.

Nick,

To preserve your remaining two good mosfets, hopefully you will add a current limit to your PSU, using auto bulbs as suggested.

Do we know or suspect that someone has a working device? I think I got the concept right and I need to ask 2 questions

Nick,

each yoke configuration has its own characteristics like inductance and capacitance caused by the used yoke ferrite, a used yoke gap if any, the primary coils dimensions,
the secondary (3 turn / 28 turn) coils dimensions, the interconnection leads inductance / capacitance, the MOSFETs output capacitance etc. etc. etc.

So for to calculate an effective snubber, we first need to have a stable yoke configuration.
It makes no sense to calculate a snubber RC value, and then use a different yoke configuration as that snubber won't work anymore.

I think it therefor would be the best to build up your new yoke using known good MOSFETs and connect it up to your inductor/grenade so we have a stable new loaded situation.
Then use low voltage on the drains and use some current limiting (power resistor / automotive bulbs) component to fire up.

Use your new scope to supply some hopefully now crisp screenshots of the gate and drain signals.
Then we can calculate any snubber RC values in trying to minimize the spikes / ringing.

Itsu

Quote from: Hoppy on August 04, 2017, 03:28:01 AM
Nick,

To preserve your remaining two good mosfets, hopefully you will add a current limit to your PSU, using auto bulbs as suggested.

yeah good idea some regulators can do it LM317 and a resistor but it will get hot once it starts to conduct.

Quote from: NickZ on August 03, 2017, 11:25:11 PM
   So I bought some more wire to finish my new yoke coil windings
  The Free motha. Well, almost free.
  So I'll be testing the reversed windings style, like Stalkers uses.
That is, where the two yoke secondary coils, are reversed from the 12 and 12 turn primary coil.
  Yep, looking for the magic...

  Itsu:
   I've made some close up scope shots of just the two fet's drain ringing signals, expanded,  to study the frequency on each one of the two ringing part of their wave form. I'll post them a little later, so we can match up the snubber values for them.
   I'll test the new yoke without the snubbers on, first, cause my FETs are junk, anyway. According to Hoppy, And they might all be bad, but there might be a couple fets that will work, for now. Anyway, the new FETs and scope are coming soon.
Hopefully, the new yoke will work more balanced, and the drains ringing signal will look more similar and flater, and having less than the 100-120v peaks that I showed previously. Then the snubbers should be able to drop those nasty peaks.

Nick, Itsu, Hoppy,  any chance you can all show your 4 turn output winding waveform ? that would be interesting, preferably open circuit. I'm sure we could all help each other that way, PS any one had anything from Geo or T1000 ?