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Problems with MiniSSTC

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Mike

Fri Apr 07 2006, 04:25PM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

Hi all. I have just finished building the circuitry towards my first SSTC.
I built all the circuitry for Steve's Mini SSTC (

). However at the moment I don't have enough wire to wind the TC Secondary, So I hooked it up to an AC flyback I had. The bridge is receiving power from a 12vac 3A (maybe not enough power?) transformer rectified, without being smoothed by a smoothing cap. When the antenna is placed closer the the secondary of the flyback, the frequency reading on the Primary of the GDT/ UCC outputs is 25khz. Moving it farther away makes it go down. I have tried wrapping the antenna around the core of the flyback, but that only gives 15khz. There is no spark output from the flyback either.
Mainly I don't really care about getting the flyback working with it, I just want to figure out weather or not the circuit is actually working. It is just hard to test without everything being hooked up since it requires the antenna to pick up the signal from the coil to actually work.

Thanks, Mike

Edit: see last post for new problems

Part Scavenger

Fri Apr 07 2006, 05:50PM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

I don't know why a AC flyback wouldn't work... 12V, 3A might be enough. You won't get much output though, I don't think. Check your mosfets, are they switching? What does the current look like in the TC primary? Check your GDT phasing where they hook to the mosfets. Is there current draw from the 12V 3A transformer?

Take your mosfets out and make sure you haven't fried them. Ground the gate to the source, then test for resistance D/S. If it's shorted, the MOSFET is dead. If not, if it's dead, the problem will usually be visible via a crack in the casing or something. If all checks out, the MOSFET is good.

To check for shoot though, take the primary out and drive the feedback circuit with an external oscillator. If the bridge draws much power, you may have a problem with that.

Hope that helps any.

JimmyH

Fri Apr 07 2006, 06:10PM

Registered Member #358 Joined: Sat Apr 01 2006, 06:13AM
Location: UCSB
Posts: 28

I thought you were actually trying to drive the flyback, not just test the circuit.

It is just hard to test without everything being hooked up since it requires the antenna to pick up the signal from the coil to actually work.

Since it's tougher to test it closed loop.... open the loop. Just use a 555 or something to drive the input (through a small capacitor or something), and see if it switches right

the frequency reading on the Primary of the GDT/ UCC outputs is 25khz

That's a good sign. If its switching, and not oscillating in the megahertz region, it's probably working fine up to that point- actually, since it's closed loop, the whole thing is probably fine. From that quote, it sounds as if you are using the frequency measuring option on a DMM or something, and seems to imply you don't have a scope.

If you do have a scope, just scope the whole thing out. If you don't, you have to get a little more tricky with your tests. You could continue to work with the flyback (do it open loop though), or you could just see if you can fry some resistors when capacitively coupled or something.

The real test comes when you get a secondary...

Mike

Fri Apr 07 2006, 06:25PM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

You are correct. I have no scope unfortunately, just a DMM as you said. that measures freq, capacitance, amperage etc.
I guess since it sounds like working I will just wait until I can find some wire to make my secondary :D

Also, is it important to smooth the power going to the bridge?
Mine is not smoothed at the moment, but I can if it needs to be.

Thanks,
Mike

Part Scavenger

Fri Apr 07 2006, 07:04PM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

Look at Richie Burnett's site. He shows what the difference is there. Basically, it just changes the form/sound/shape/and possibly efficiency of the streamer.

You might want to consider getting a scope. You can find a decent one on ebay for 50 or under probably. They're VERY handy. Also, I would definitely build a signal generator like Jim said, they're well worth the minimal effort.

Dr. Drone

Fri Apr 07 2006, 08:48PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
Location:
Posts: 1673

Desmogod

Sat Apr 08 2006, 03:26AM

Registered Member #139 Joined: Sat Feb 11 2006, 11:01AM
Location: Perth, Western Australia
Posts: 358

I third that :P Buy a scope, if you have built an SSTC, you will build something else, and it is an invaluable tool. I don't know what I would miss more, my DMM or my scope. To be honest, it'd be the scope. I picked up a crappy DSE unit for $30 out of the Quokka (Trading Post)
Being able to see what the circuit is doing is essential when you are debugging the circuit.

Sat Apr 08 2006, 03:28AM

Registered Member #256 Joined:
Location:
Posts: 124

i must need a scope here in the future then, because i too am planning to build a sstc

HV Enthusiast

Sat Apr 08 2006, 03:42AM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

streamers rule wrote ...

i must need a scope here in the future then, because i too am planning to build a sstc

Although a scope greatly helps the effort, you can build an SSTC without one. I think most the people here built their first SSTCs without an oscilloscope. But yes, an oscilloscope makes it much much easier and you can see whats going on with the coil during testing.

Mike

Thu Apr 13 2006, 09:41PM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

Okay, well heres whats been going on,
A few days ago i finished it, got it working, fed it full power
It worked for a little, i turned it off, and then later turned it on, it made one streamer then stopped, i noticed the 7812 died, and i noticed conductance on the board after removing all components, so i scrapped that and re built it on perf board. its all hooked up and it was working well on 12v 3a with a small spark, and then someone suggested switching the ucc chips around to see if that made the output better, it didn't, it didnt work at all, so i put them back as I had them before, still wasnt working. As of now I am using a 50khz 555 feed into the antenna 50% duty, i get that freq on the output of the hex inverter and on the output of the UCCs/GDT primary
but theres no output on the secondarys. So a little later i try it, and i get the freq on the secondarys now, so then i put power on the bridge since i had disconnected it before, and nothing, the GDT isn't giving out the signal on the secondarys. Im quite confused, I may just make another GDT, any suggestions?

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