Hi Nick. It does look like what you are getting in the yellow trace is unwanted
oscillations, which are also known as parasitic oscillations. I personally don't think
this is the kind of effect you are looking for in these type pf circuits, and it is a good
way to kill transistors, as you know. 

The duty cycle measurement will not work well if the square or rectangular waveform is
not fairly clean, so that may be the problem there. Also if a waveform is very jagged
or irregular, it can be hard to get stable triggering on your scope. In such a case you can
try triggering on the other scope channel if it has a cleaner or more regular waveform.
Try different trigger level settings to see which trigger level works best.


lost_bro: In one of your scope shots it looks like you possibly may have been picking up
something like a clock signal from some electronic equipment near by, as it looks like
a rectangular wave.

Nick,

Can you increase the 'effect' (both bulb brightness and stronger fluctuations with hand movements) by disconnecting one side of the push-pull and at the same time reduce the mosfet heating? Try disconnecting one side at a time to see on which side the 'effect' is best. Disconnect at the mosfet gate. I achieved a better 'effect' by running on a single mosfet.

   Hoppy: 
   I've been trying to get the Radio Moscow signal back, which I still have not been able to do. As there is something different and special about that condition. But, I'm trying to get the same effect without going into the avalanche. As that is a no no, and can't be the way to success. I can easily tell which fet is avalanching, just by looking at the scope. And of course it has higher output, up to 350v. But, that output is not where the magic lies, but is where component failure happens, instead.

   Apecore has already tested your idea of running on a single fet, and has made a video of it. I'm not into doing the same tests. If only one fet was better than both fets, these devices would be made using only one. But, they aren't, so, I don't see the point.
I would like to see someone outputting several hundred watts, and not heating up their fets. And also being able to produce use able and adequate output, and not just barely lighting the bulbs, at 20% of normal grid lumin levels. Like Geo has been showing, limited to only 5 amps, no matter how many bulbs he has connected up. Yes, he could light a 50w bulb similar to the grid lit bulb.
But, not the 100w, 500w, nor 1000w bulbs.
   
   Itsu mentioned that he can run his yoke/grenade set up without heating of snubbers. But, the heating comes mainly when the Kacher is also fired up at the same time. Which he can't test for, as yet.
   Now I undestand Itsu's point, as in one of my tests, my PC speakers which at the time was connected to my cell phone to listen to some music on, started making strange interference sounds. It's located about 3 meters away from my device.
   
   So, Itsu. What steps should be taken to protect my new scope from the dangers of HV. As I'm pushing 5000 to 8000 volts from the Kacher's output.
   
   I've also found that I can get into the avalanche setting at almost any voltage level, even between 150 to 200 volts. But, now I don't see any benefit in letting it run in that way. As there is NO extra light output, at least not very much, only lots of extra heating of the snubbers or fets. So, I will discontinue looking for magic where there is none. And focus on getting Radio Moscow back, which is "lost in space", still.
Danger, Will Robinson. Danger...

Hi Nick, there is no certain way to ensure your scope won't be damaged when operating the
Kacher/tesla coil, but there are a few things that can help to minimize the risk.

Make sure the scope itself is at least two or three feet away from the high voltage parts of
the circuit, and any scope lead wires should always be arranged so that they are no closer
to high voltage parts of the circuit than about a foot or so.

Use a x100 or x1000 scope probe where voltages can be higher than 400Vpp or so.
It would be best to have a x1000 scope probe if you are connecting a scope probe
directly to points in the circuit when the kacher is running and connected in, just to be on the
safe side.  A x100 scope probe is usually rated around 2kVpp max, and x1000 scope probes
may be rated up to 8kV or higher, depending on the type of waveform.  Also make sure your scope
is connected to an AC outlet that has the third ground prong, so your scope is grounded.

Unfortunately, anytime you are using electronic equipment around high voltage circuits there is always
risk of damaging the electronic equipment. I have blown a x10 scope probe in the past by being
a bit careless, but luckily I have never yet damaged a scope in my high voltage experiments, although
I have damaged my bench power supply when testing with a kacher circuit a few years ago.  It's
safer to power your circuit with a battery when running the kacher circuit. I find it also helps to earth ground
the battery or power supply negative DC terminal when working with kacher circuits and similar.
If I had done that a few years ago when testing with a kacher circuit, I may not have blown my bench power
supply.

But, now I don't see any benefit in letting it run in that way. As there is NO extra light output, at least not very much, only lots of extra heating of the snubbers or fets. So, I will discontinue looking for magic where there is none. And focus on getting Radio Moscow back, which is "lost in space", still.
Danger, Will Robinson. Danger...

Now you are talking. I hope one of these days in the near future I can show a real
OU effect, but despite some interesting things seen so far, it is of course much easier said
than done demonstrating genuine OU. 

   OK, Void. Thanks for the info.
  Problem lies in not being able to read the numbers or able to reach the knobs when the scope is 3 feet away.
I have it about two feet away, where I can see it and reach it. I hope that it's far enough away.
  BTW: My Tectronix scope just bit the dust. So, I'm concerned about the Siglent.

Yep, always a risk, particularly with digital scopes. My scope usually sits within about two feet
of the circuits I am testing with so I can reach it as well, but be very careful where the scope
probe lead wires are sitting, because if they get a bit too close to high voltage something
potentially could get damaged.    After about six years or so of experimenting with high voltage
circuits off and on, my Siglent scope is still undamaged. Knock on wood...

   Itsu:
   Remember that I also have the MUR1530 between the source and drains.
   If those scope shots are not the avalanche that I can see, I don't know what is happening, then.

   You are right about the HV not affecting the TL494 or driver voltages, it doesn't affect them. But the snubbers resistors DO heat up when the Kacher is also on, and a heavy load is used, like 300w or higher. Using a smaller bulb, such as a 100w bulb, lights to blinding output. It takes me a minute or two to be able to see anything again, afterwards.

   The snubber resistors will start to smoke after one minute running time, or less. So, I doubt that the new carbon resistors that I'm waiting on will make much difference. But, we'll see.
   In any case, I'll do whatever it takes to get this working right.
   
   My older scope is dying, of old age I think. But, it still shows a dim signal, for now, and so is still somewhat use able, I hope.
   I'll use my single 100x probe on the new scope, for now.
   
    Thanks for your advice, guys.

Have a look at the two pic's they are of a C-Mos Logic emulator.

It works on a Katcher VFO clock driver (tuned coil required) and a divide by 50 + 2 +2 to give an EW push-pull drive with variable dead time using 5 logic chips + 2 added drivers not shown.

So if Katcher was for the sake of argument was 2 Mhz the push-pull would be 20kz (10 +10 kHz).

Notice the dead time.

Allen