Attempting the Kaizer sstc II

[Mads Barnkob]

The core for your GDT is fine, N30 material and the physical size is good enough.

Regarding using the oscilloscope, you should at least watch this, and also some of the other introductions to oscilloscope videoes that Dave has on his channel:

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The square wave going into the primary of the GDT is the first shot? That looks okay.

The second picture shows a duty cycle over 50% and thus can not be a correct signal to either drive a GDT with or get out from the secondary side of it.

The third picture clearly shows that something is not right in the driver -> GDT -> gate setup, you should see a square wave here, maybe with some minor oscillations, peaks or roundings of the edges, but it should be a square wave.

I have, when I first started doing electronics, had to give up and on a circuit and start all over from scratch, because you might have multiply errors that keep interlocking each other, so even if you fix something you can not see an improvement. You have to just work your way out from left to right. Feedback -> driver -> GDT -> gate drive -> inverter output and make one thing work before moving on.

You can make a half bridge, that is no problem, check out the SSTC1 on my website.

[nabzim]

I have some enamelled 0.5mm wire should I use that instead or stick with Ethernet wire.

When I was trying different GDT winding methods, a couple times I tried I using magnet-wire. The insulation is so fragile, that just the process of winding it on the core actually scraped some insulation off the wire, and I ended up getting arcing between wires, and they were little purple sparks. So there must have been a high voltage induced in the GDT windings I think. So from that point on I vowed to always use wire with real insulation, and I just spent the money to buy a small roll of cat5 from home depot. It was 24awg solid core,
 Which works good, and I even recently bought another roll but with stranded wire, so I can use that for all sorts of stuff too. (I highly recommend the Ethernet wire. It gives you 4 different pairs of wire and they're already in twisted-pairs AND they're already all color-coded differently for you) it is worth the small investment, then you will also have that wire to use for routing signals and/or power for anything else you want.

[futurist]

I agree with nabzim about using ethernet wire
Strip it by hand after heating with lighter, to avoid scoring the wire

[CCX191]

Thanks for the input I have a bunch of Ethernet cables laying around anyways and they are really cheap here.

I redid everything and converted it to a half-bridge to save my time so it's the Kaizer SSTC I now !
I have seem to maybe actually point out one of the issue. I have several UCCs lying around.. One set from 2 different sellers from China and a set from element14 but one is from the US and one is available locally.. all of  the 21s and 22s are different.

Is there a possibility of compatibility issue with them? At most of the combination.. the 22 will get extremely hot while the 21 stays cool. At the GDT it does not resemble a square wave at all but like the third picture of the scope from my previous post. At certain combination nothing will be produced. A little step to progression again
Or, could the 74HC14 be faulty?
Oh, how would I be able to test the 74HC14 though? I've grounded the unused input pins which are 5, 9, 11, 13?

[Mads Barnkob]

UCCs heating up is never a good sign, it is either shorted internally or oscillates because of a wrong connected load.

Cheap ICs are often not fake, but could be low quality rejects from factories. If they are fake, it is often "same" kind of IC but with lower ratings, even if you had some fake with only 3A peak power output, it would "work" for this driver. My own experience with UCCs failing/not working is that I made a mistake at the GDT so that they are not loaded correctly or the input/enable was wrong.

74HC14 testing: feed it with a sine wave and see that a inverted(or normal if you have two inverters connected in series) square wave is outputted from when the rising edge of the sine wave passes the threshold voltage of the 74HC14 input.

[CCX191]

Thanks! One of the UCCs heated up as it probably is shorted internally. (Maybe not)
I guess those cheap UCCs are probably defects. They seem to not work properly at all.
The heating up seems to have some relations with the 74HC14 if that is working properly or not

For the 74HC14 I have replaced it and have gotten slightly better results.

This is what I get on the bridge gate and source

You can see the legs of all the dead Fets of the bottom right
It's slightly taking shape of a square wave.. but I'm probably sure I'm not quite there yet( or else usually at other times there will be just lines all over)

[CCX191]

Great news!

My GDT produces a nice square wave now and now it is running at a half Bridge configuration.

Here's a picture During testing.


It's running pretty well.. except that I've run into this issue where there will be sparks at the tip of my antenna at times. Anything that should be done?

[oneKone]

Great news!

My GDT produces a nice square wave now and now it is running at a half Bridge configuration.

Here's a picture During testing.


It's running pretty well.. except that I've run into this issue where there will be sparks at the tip of my antenna at times. Anything that should be done?

I've been quietly following and it's awesome to see improvement!

As for the antenna try a longer breakout point, and maybe move the antenna a bit further. I've had that problem before when I made a small sstc with a largish topload.

[Mads Barnkob]

Did you find out why it failed to work before?

I agree with oneKone, move the antenna further away from centre of the coil and shorten it to be further away from the topload. I had mine so that there was visible corona on the tip of the antenna when running full power.

[CCX191]

I'm actually not entirely sure. All I did is swap my current DC blocking cap to a MKP x2 type capacitor that I bought for extra.. it's rated only 300v tho and it started to work.

The cap I was using back then: goo.gl/wL9snH
Current caps I'm using: goo.gl/3NLiJi

Since the cap is rated at only 300v now. At what limit should my variac go?


Regarding the antenna I think the right term I meant was the visible corona. Should I be concerned over this? I can slightly move it away for sure.

Now i'm planning to just get my audio modulator to work. I see that user E-Schmok has a video on using a Toslink mini jack here: goo.gl/xwiL9w which I'm not entirely sure how to get it to work. If not I will just use a 3.5mm jack or so. Any safety precautions I should be aware of? I have a 6N 137 opto isolator but i'm not entirely sure if it's applicable or how to wire it.

[nabzim]

It's running pretty well.. except that I've run into this issue where there will be sparks at the tip of my antenna at times. Anything that should be done?

that was also happening on my coil (I can now see its very common, from Mads' and oneKone's replies) . It never seemed to do any harm, but I still did few things like: i curled the tip of the antenna into a loop to make it nice and round, then covered the whole thing in kapton tape because it was just bare 12 awg copper wire. but there was still corona through the kapton tape, so ultimately, I ended up just adjusting the distance of the antenna until the sparks didn't occur anymore. but that also reduced the actual output of the coil a little bit also, so you pretty much just take the good with the bad

[CCX191]

Yeah. I have observed it for a bit and it doesn't seem to do harm as mentioned. The opportunity cost here is real 

[oneKone]

Hey,
Have you made any more updates/progress with this coil?

[CCX191]

Hey,
Sadly no    I'm having exams now till November and then I will finally be out of high school and I can continue to work on it and some other projects I have been planning to work on. As of now I will just float around here

[oneKone]

Cool,
Goodluck with the exams.