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Question on Flybacks

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Question on Flybacks

Unread postAuthor: Unbreakable » Sat Mar 29, 2008 9:22 pm

So, I went digging around in my garage and found an old TV that had stopped working after we'd dropped it (lol).

Now, it's a rather old TV, around 1993 but it has a flyback that looks almost identical to this one that was in another post: Image

Mine has 2 minor wires coming out of it, and then the usual HV wire. I read the website guide at sixmhz.com but I'm still having a little bit of difficulty discerning how exactly to "test" for the primaries and feedback and such. I bought wire connectors for a 9V battery adapter, so how exactly would I hook this up to the flyback so I can test the arcs for the primary, feedback and secondary coils?

I'm trying to get this circuit put together:
Image

As demonstrated by jimmy101.
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Unread postAuthor: TurboSuper » Sat Mar 29, 2008 9:57 pm

Use the diode test feature on a DMM (or an LED and a resistor if you're real broke) to find two sets of pins with continuity.

Some may have multiple connections to the same coil, so mark down which pins have continuity to where.

After that it's a joyous process of trial and error.
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Unread postAuthor: starman » Sat Mar 29, 2008 10:09 pm

Take care when working with a TV flyback, especially ones still connected to the TV. Many an oldtimer TV technician bought-the-farm getting shocked by those things while still connected to the picture tube.
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Unread postAuthor: Unbreakable » Sat Mar 29, 2008 11:36 pm

Should I wear insulated (rubber) gloves while handling it then?

Also, to test the flyback, should I create the other parts of the circuit and begin from there?
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Unread postAuthor: starman » Sat Mar 29, 2008 11:50 pm

Unbreakable wrote:Should I wear insulated (rubber) gloves while handling it then?

Also, to test the flyback, should I create the other parts of the circuit and begin from there?


Your big danger is a picture tube discharge into and through your body. Yes rubber gloves on, reach in and under the anode sucker with a screw driver that is grounded to the tv chassis, being sure you touch the metal pin of the anode. If you hear an arc, then you have discharged the tube. If you hear nothing everything is safe.

If you have it out of TV already, you are good to go.
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Unread postAuthor: Unbreakable » Sat Mar 29, 2008 11:58 pm

Ah yes, it's being removed from the circuit board thanks for the warning on that.

In regards to wiring, is 30 gauge solid conductor wiring good enough to use for a circuit such as this? I had worried that the electricity would simply ignore the insulation... Hopefully I'm wrong about this?
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Unread postAuthor: starman » Sun Mar 30, 2008 12:13 am

Unbreakable wrote:Ah yes, it's being removed from the circuit board thanks for the warning on that.

In regards to wiring, is 30 gauge solid conductor wiring good enough to use for a circuit such as this? I had worried that the electricity would simply ignore the insulation... Hopefully I'm wrong about this?


30 gauge is a little small to work with reliably, but will work fine on the low voltage sides of the circuit. Use a bigger gauge thick insulation wires on the high voltage output of the flyback. The thick red anode cable that was used in the TV set will be ideal for this.
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Unread postAuthor: Unbreakable » Sun Mar 30, 2008 6:01 pm

So I'm testing for the primary coils right now, but what does it mean if there are more than one combinations that have 1 Ohm resistance? Does this mean any of them could be my primary?

Are the feedback and primary loops interchangeable?
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Unread postAuthor: Unbreakable » Sun Mar 30, 2008 6:33 pm

Ok, so I got it together... And I'm afraid I went a little crazy with glee when I saw that spark...

I fear I may have overdone my circuit... I wasn't satisfied with the 9V so I hooked it up to a 12V power supply and shortly after the spark died and now the HV cable will not produce a spark from the secondary 0V coil pinout...

Did my transistor die? I'm using a 2N3055 and it was very hot to the touch after the spark died, but it wasn't so hot it would burn your skin...

Please help! I am so mad at myself because this is due tommorrow and I think Radioshack is closed -_-
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Unread postAuthor: rp181 » Sun Mar 30, 2008 6:55 pm

i doubt that 12v burned the flyback, the transistor, mabey. Did you put a heatsink on the transistor? if not, it probably died. search 555 flyback driver, there more effeciant and powerfull. Wind your own primary if your not sure on the built in one, just wind a few coils on the exposed ferrite.

The closest i got to driving a flyback was putting it on a tesla coil circuit powered by a mot. kinda pointless but cool =)
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Unread postAuthor: TurboSuper » Sun Mar 30, 2008 7:12 pm

Well, the only way to know to know is to troubleshoot:

http://www.stickycarpet.com/pinx/test.html tells you how to test a transistor with a diode test, or you can use the transistor test feature of your DMM if it has one.

I'm with the guy above me, I doubt 12V blew your coil. Best to start with the transistor.
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Unread postAuthor: Unbreakable » Sun Mar 30, 2008 7:27 pm

Roger, thanks everyone!
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Unread postAuthor: starman » Sun Mar 30, 2008 7:56 pm

Take your transistor, I assume its a 3055, and using an ohmmeter on the 1 scale, test between the 2 legs protruding, emitter and base...then turn the probes around (switch polarity) and make the same measurement. You should get an open or (close to it) one way and a short (or close to it) the other. If you have a short both ways, you blew it. You can also do this test between each pin and the case (Collector) and you should get similar test readings. Any reading where there is a short both ways...toast.

You can't run those things without a heatsink. You'll need a TO-3 insulator ( I assume that is your form factor) and thermal grease. If you have a TO-220 form factor just get the insulator and heat sink the fits it.

Heat sink = Big A chunk of metal, usually aluminum...just get one predrilled for your form factor.
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Unread postAuthor: Unbreakable » Sun Mar 30, 2008 9:32 pm

I got it working!

I'm so proud of myself :D Unfortunately the transistor was inadequate (i believe) and the spark is not very impressive on a 9V source. It does not produce a strong enough spark to ignite the particular fuel i was using (can of AXE deoderant) AXE has worked for me in the past in smaller scale (pen launchers) so I assume that there just isn't enough voltage to ignite it in the chamber...

The spark gap is something like 1 CM with a 9V, I tried using a 12v power supply but it worked like twice and then died on me. The spark extended to about 2.5cm when the 12v source was working.
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Unread postAuthor: rp181 » Sun Mar 30, 2008 9:42 pm

1 cm? that is bad. Are you using a 9v battery? u may need more current.
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