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Michalis.Biochem

Sat Oct 30 2010, 03:35PM

Registered Member #3340 Joined: Wed Oct 20 2010, 07:28PM
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Posts: 69

Wow, 1000 Watts would be too much for me. Considering that i have batteries as power source

I am going to try to find the flyback you described. I will keep you updated.

Adam Munich

Sat Oct 30 2010, 04:29PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

That was from batteries too, SLA ones. Keep in mind the bank weighed 170lbs.

A nice thing with flybacks is you can easily adjust the power by limiting the input current. A 50 watt ZVS with small MOSFETs and an AC flyback could be perfect for a tiny SGTC.

Some projection TVs have the voltage cascade (thing with focus knobs) separate from the transformer, which means they are AC.
Computer monitor FBTs output DC, so you'll need to design a DC coil for those.
The small FBTs in the 5" sets are DC.
If you are unsure what the polarity of a flyback is, make a polarity tester. I use a neon lamp in series with 6 22megohm resistors. The negatively charged electrode will glow in a DC circuit, while both will glow in an AC circuit.

Edit: Whoops I found it and it has 6 resistors. It has tap points for different voltages. Here's a pic. Even though they are printed as 20MOhm, they are old so they read 22.

william L

Sat Oct 30 2010, 07:09PM

Registered Member #3093 Joined: Mon Aug 09 2010, 11:40PM
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Not all of them die instantly. In fact I have 3 of them with protection diodes --only the really cheap chinese ones omit the diode.

You're right, they can't supply much current. However I did find one that I was able to draw 1.5cm arcs from. It only supplied 3kV so there must have been quite some current there. I can't find the exact one, but here is one like it, even though I loathe egay/payfiend. These people accept credit cards though.

OH, I've only had experience with scanner bulb drivers. That looks like a neon driver, but I guess they are practically the same thing, given the slightly differed circuits.
Here is the scanner module:

where as the neon looks to use a mosfet and oscillator.
If you use the scanner type, remember to solder a jumper across the hv limiting cap, C3. But this will stress the module. otherwise, Good Luck!

Steve Conner

Sat Oct 30 2010, 08:18PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Grenadier wrote ...

Computer monitor FBTs output DC, so you'll need to design a DC coil for those.

All flyback powered Tesla coils have to be DC. Only DC flybacks are usable. Likewise a CCFL driver would have to be rectified.

(A cookie for anyone who can explain why.)

Edit: see this

803

Sun Oct 31 2010, 02:57AM

Registered Member #2807 Joined: Fri Apr 16 2010, 08:10PM
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Posts: 191

There is so little power in these things, one pulse can't charge the cap enough.

Do i get a cookie?

Michalis.Biochem

Thu Nov 04 2010, 09:53PM

Registered Member #3340 Joined: Wed Oct 20 2010, 07:28PM
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Posts: 69

Ok, i got an update. I might manage to get one of those little flybacks that are in the 5" tvs, but i need to know the components that a mini ZVS driver consists of(like grenadier said).

Thanks in advance

Adam Munich

Thu Nov 04 2010, 10:05PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Well before you consider building a ZVS, you need to make sure the FBT has an open core. If it doesn't you can't wind a center tapped primary and thus no ZVS.

In those mini TVs, it's a gamble as to whether the ferrite is open or not. Computer monitors are usually always open cored.

Components for a zvs depend on how powerful you want it to be. Higher power = Bigger MOSFETs. However, a zvs would still need (2) >400V ultrafast diodes, a .68uf >200V cap, 2 10k resistors, and 2 12V zener diodes, and a 47-200uH inductor.

You can get the inductor from a computer PSU.

Edit: Here's what I mean.

Here are two 5 inch TVs. The white one has a "closed" FBT, while the other has an "open" FBT. The open one can be used with a ZVS, the closed one requires a circuit based on the 555 timer or some other oscillator. Don't expect too much power from a closed one, but it should be able to power a (really) small SGTC.

Michalis.Biochem

Thu Nov 04 2010, 10:51PM

Registered Member #3340 Joined: Wed Oct 20 2010, 07:28PM
Location:
Posts: 69

Grenadier wrote ...

Components for a zvs depend on how powerful you want it to be. Higher power = Bigger MOSFETs. However, a zvs would still need (2) >400V ultrafast diodes, a .68uf >200V cap, 2 10k resistors, and 2 12V zener diodes, and a 47-200uH inductor.

I think that the capacitor need to be a non-electrolytic one or else it will blow up and that i can make the inductor myself.
As for the other parts, are they standard(with the same values) for any FBT?
And what type of MOSFETs would i need to buy if i have a 12V power supply(batteries)?

Also, thanks for the fast response

Adam Munich

Thu Nov 04 2010, 10:59PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Yes, it needs to be an MKP or mylar cap, an electrolytic will go boom.

The other parts are standard.

As for the FETs, they depend on how many amps you want to push through the xformer. If you want to send less than 150 watts through the FBT then the IRFP460 would be a great balance between price and toughness.
Also a tip: Get some extra FETs. Blowing them up and then having to wait for new ones in the mail is never fun.

Michalis.Biochem

Thu Nov 04 2010, 11:08PM

Registered Member #3340 Joined: Wed Oct 20 2010, 07:28PM
Location:
Posts: 69

Now it seems that the main problem is the FBT. I am going to buy the other parts tomorrow(and a 555 timer just in case)

Thank you very much for the info.
Btw, i acquired a broken sound amplifier. Does it have any part that is of interest?

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