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Flyback with single 2n3055 with weird repeating sound

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Zee

Tue Jul 03 2007, 09:42PM

Registered Member #877 Joined: Tue Jul 03 2007, 09:15PM
Location:
Posts: 21

First-timer here, some experience from low voltage electronics but new to the interresting world of high voltage.

Decided to give a go for the flyback transformer driven with the basic single 3055 circuit from a 12V 1.6A source.

I haven't blown transistor yet, but neither have I been able to create any arc yet.

I got the flyback brand new but it was missing the HV outlet. Since the cavity in the casing had a rubbery like bottom with a tiny hole in it, I assume the HV cable is supposed to be just inserted there. I currently have a piece of regular cable taken from an old PC psu used as the HV output. For the other end I assume the only pin at the bottom of the flyback that didn't seem to be connected into anything else is the correct one. (And yes I have been zapped several times in the past from old videomonitors that I know what to touch and what not when live/charged.)

The primary (5) and feedback (3) windings are made (didn't use the built-in ones) from a plastic coated single stranded wires (sorry but I don't know how determine the AWG of a wire), both wound the same direction, and when the circuit is active I can read about 90V over the primary winding.

Now for the sound part... When I connect the 12V transformer I hear a tiny repeating "snapping/tapping" sound from the flyback, repeating about 3-4 times a second. When the power is switched on it takes about a second before it starts doing that. I've been trying to google for such symptoms and search from this forum without any recognisable results so far.

So any ideas from the more experienced ones?

Zum Beispiel

Tue Jul 03 2007, 10:15PM

Registered Member #514 Joined: Sun Feb 11 2007, 12:27AM
Location: Somewhere in Pirkanmaa, Finland
Posts: 295

Sounds like the flyback is arcing internally. The 4Hz repetition rate could be caused by the internal capacitor charging/discharging.

What is the flyback for (TV, monitor)? Maybe it was replaced, that could explain the missing HV output wire (the new one didn't come with one, so the old one was used).

Zee

Wed Jul 04 2007, 09:34AM

Registered Member #877 Joined: Tue Jul 03 2007, 09:15PM
Location:
Posts: 21

With brand new I meant it has never been used before. Bought it from a local electronics store that has a surplus of various kinds of electronics stuff and boxloads of flybacks of different kinds.

Matthew T.

Wed Jul 04 2007, 10:30AM

Registered Member #513 Joined: Sat Feb 10 2007, 07:30PM
Location: Pointe-Claire, Quebec, Canada
Posts: 19

Hey Zee,

Try switching wires around on both the feedback and the primary. I've never used that circuit (went strait to ZVS) but that's what the few sites that have that circuit posted seem to suggest.

Good Luck,

Matthew

Zee

Wed Jul 04 2007, 02:38PM

Registered Member #877 Joined: Tue Jul 03 2007, 09:15PM
Location:
Posts: 21

Ok, tried swapping the feedback and primary connections around but still no arc. Instead the slowly snapping sound I got earlier is now very rapid, but only sounds when I have the HV and 0 wires put close. When they're apart it doesn't make any sound.

D'oh, I want to hear it squeal. :(

Zee

Thu Jul 05 2007, 11:32AM

Registered Member #877 Joined: Tue Jul 03 2007, 09:15PM
Location:
Posts: 21

Extended my HV cable a bit and tried going through all the pins at the base of the flyback. It pretty much sparks into anything it comes close with but I still can't get it to arc. The whining is still missing.

I also gutted one old b/w monitor and using it's whole transformer and components I get a lousy 15kV 5mm arc, but I really would like to get this bigger TV flyback working.

Thu Jul 05 2007, 11:52AM

Registered Member #809 Joined: Wed May 30 2007, 08:59AM
Location: Melbourne, victoria
Posts: 114

does it sound like a clicking noise?, if so check the core, is it loose? also what are you powering it off? if it's a switchmode transformer, sometimes they have short protection. with my flyback, the core was loose, and my transformer was a switchmode one so it pulses the output a couple of times, making the core smash together. just a thought?

uzzors2k

Thu Jul 05 2007, 11:53AM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

It might not arc because of too little power, 5mm is only 5kV. To arc your driver needs to supply sufficient current to sustain the arc. If the snapping noise synchronized with the sparks nothing uncommon is happening, rectified flybacks have an internal capacitor, so each spark gets a boost making it loud. This is also why rectified flybacks don't arc at low power, but only spark. The capacitor has to be charged to the breakdown voltage of the gap first, and this takes time. Also your new HV connection might be loose by 1-5 mm, which still lets it spark, but not as long as it could have.

Zee

Thu Jul 05 2007, 02:18PM

Registered Member #877 Joined: Tue Jul 03 2007, 09:15PM
Location:
Posts: 21

The 5mm arc comes from the old b/w monitor hardware. When switching it on the arc can leap a 5mm gap, but when it's running the wires need to be at 1mm before it arcs, after that, with good grounding, I can draw the arc to about 15mm. Been frying things with it all day now. Except the really high pitch it makes is also damn loud.

For the TV flyback that I'm trying to get working, the 12V 1.6A PSU is over 30 years old, but maybe it's underpowered. But I remember reading somewhere that someone was able to get his flyback to arc even with a 12V 800mA PSU. It could also be those windings of mine. But the HV lead is surely in place, with the end of the wire soldered and stuck into the rubber thing and then some small pieces of plastic inserted to the neck of the flyback to keep it from coming loose.

The core is in good shape with all the spacers and all. haven't taken it apart either.

With the monitor hardware I can fry the surface of a CDR in the instant both wires touch it, but the TV flyback doesn't even spark into it, so it's really running low on output voltage.

D'oh, I should've gotten some other flyback models too to test with.

Thu Jul 05 2007, 11:38PM

Registered Member #809 Joined: Wed May 30 2007, 08:59AM
Location: Melbourne, victoria
Posts: 114

Zee wrote ...

D'oh, I should've gotten some other flyback models too to test with.

That was exactly my thought when my flyback didn't work.
Oh, what are "core spacers"

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