"The effect seen here is, magnetostriction causes the core to expand.  It expands uniformly, which can be seen as a superposition of many acoustic resonances propagating in both directions (clockwise and anti- around the ring).  Intuitively, I don't see that this should cause a problem -- but, if there happens to be just enough nonuniformity to prefer a standing wave, it will develop as the difference between the others.  Possibly there could be a feedback mechanism where the motion of resonance affects the strain of the effect, I don't know."
     end quote.


   Hoppy:  Interesting deduction...

   You had asked me for a scope shot of my gate signals, so, here's one (BELOW) taken on my new scope.
The TL494 circuit is working fine now along with the tiny 4420 fet drivers. It's something with the yoke that has things heating up, I guess. So, that's where I'm hung up at the moment.
   In any case, I'll make another video soon.

It could be that although the effect of the Kacher is not strong enough to show any appreciable illumination of the bulb, it may be enough to shift the B/H curve of the ferrite enough to show control of the bulbs illumination when the push-pull is running (whilst in RM mode) when using Geo's new Kacher control board, that has both frequency and pulse width control. There may also be hetrodyneing involved.

PS. Thanks for showing your gate waveforms which look fine. Are you limiting the current draw from your PSU?

  My Kacher does show an increase in bulb brightness, and heterodyning effects, even in the non RM mode.
But, as my Kacher will light a 50 to 100w bulb by itself, I have to take that into consideration, also. And not allow that gain to fool me at lower loads. However, using 200w or higher loadings, I see little effect from the Kacher. Unlike what Geo was showing previously. I get lots of bright output at lower loads, even without the Kacher. And can even make the yoke ring, but only with the Kacher on, do I get the RM signal, that can change tones with hand movements, etz... However, I don't see that effect when using higher (200w plus) loads, as yet.
   And, just where to place the earth ground connections, (I use two), can also affect things, also.

  I can get a great looking clean square wave signal at my drains, but there's no magic using a clean square wave signal.
There needs SOME ringing going on, instead. Also an equal sharing of the wasted heat between the fets, RC snubbers, and the Oleg snubber resistors. So, it's a tricky balance to get it all just right. It does take much time, most people would just give it up.  But, not me...

Quote from: NickZ on September 30, 2017, 01:56:28 PM
  .... And can make the even make the yoke ring, but only with the Kacher on do I get the RM signal, that can change with hand movements, etz...

That would be consistent with heterodyning.

  I corrected that last post of mine, so that it reads right.

  Funny thing, here I'm working on my rig, and it's running at around 15KHz, or so. And my daughter comes into the room and from across the room she says, oh,  that awful noise, again.  But, I hear nothing, even though I'm right next to it. Getting old, I guess.
Sometimes getting old has it's benefits, like not hearing the awful ringing noise, "like the sound that old Tv's use to give off", she says.
        Or, from the ghost channel.  Radio Moscow