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question about the internal circuitry of a Flyback

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Captain Proton

Fri Nov 18 2011, 09:21PM

Registered Member #3506 Joined: Sun Dec 12 2010, 02:48PM
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Posts: 8

Hello there, i've just made my 2nd flyback driver. using a 555 running a mosfet (quite proud of it too, 2+ cm spark off 10v ^_^) and i was messing a bit around with it.

One thing i did was sending the voltage through a home made coil i had lying around, without actual contact (sparks from each electrode to each end of the coil) and i found out that if i put the "output" wire of the flyback 1-2mm from one end and manually adjusted distance between the other end of the coil and the "input wire", i would get this purple corona emanating from both coil and wire, forming sort of a little purple sphere.

*To the point*

it was then i noticed that this electron spray also occured between one of the 3 seperate pins on the flyback ( by seperate i mean the ones not included in the "horseshoe" pattern), which it also would do if i simply pulled the 2 electrodes far away from eachother, so it has nothing to do with beforementioned coil.
I then tried to isolate said pin with hot glue, hoping that i'd get a better output from the flyback , but i lost the "ability" to make the corona and didn't see any improvement on the overall, i then removed the heat glue in fear of the pin being isolated might cause internal damage.

*Actual question*

Can anyone tell me why this is? that said pin "sprays" towards the negative end of the flybacks secondary, or better yet can explain the actual internal circuitry of a flyback transformer?

The Flyback i'm using is from a 10 year old Philips computer monitor.

Thank you for your time :)

ifryd

Fri Nov 18 2011, 10:09PM

Registered Member #4215 Joined: Wed Nov 16 2011, 09:45PM
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Posts: 32

Probably you get that sparks on your transformer only when you try to make big spark gap so the secondary is not withstanding that high voltage. Also be careful with ozone while playing with open spark gaps...

Captain Proton

Fri Nov 18 2011, 10:34PM

Registered Member #3506 Joined: Sun Dec 12 2010, 02:48PM
Location:
Posts: 8

oh i am aware that the spark/spray on the pins only occur when i pull my electrodes too far from eachother,, I am just wondering why the spray comes from the internal capacitor or whatever is at that pin.

I am also aware of the ozone, i've got an open window about a meter and a half from the sparking ;) thanks for the concern though :)

Patrick

Fri Nov 18 2011, 10:54PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

You can get an internal schematic for your flyback if you have the numbers, then check HR.diemen

Inside that flyback you have is a series of pots and resistors, and a few diodes and caps to boost / rectify the polarity from the flux lines collapsing to cuase the cemf, and then a buch of side coils for other voltages for support circuits in the mointor.

to solve tthe problems your seeing i put mine in an oil tank.
look here ->

Captain Proton

Fri Nov 18 2011, 11:15PM

Registered Member #3506 Joined: Sun Dec 12 2010, 02:48PM
Location:
Posts: 8

Thank you very much for your answer, i was able to find the schematic of my flyback :)

I'm quite new to flybacks, so i'm basicly just messing around for the moment, but i'll keep your setup in mind, very nice idea to use oil for cooling and insulation :)

Antonio

Fri Nov 18 2011, 11:15PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

The pins out of the horseshoe pattern are the ground pins of one or two potentiometers and a capacitor, usually. They are connected to the HV terminal at the other end. If the ground pins of the potentiometers are left disconnected, they are at the HV potential, and produce corona to the low-voltage terminal of the main coil. Just connect them to the ground pin. (You may want to leave the terminal of the capacitor disconnected, because if you connect it to ground instead of corona from the HV output you will have series of strong sparks, and a very nasty shock if you get in the discharge path).

Proud Mary

Sat Nov 19 2011, 01:11AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

In a quick random sample of HR Diemen LOPTs, I haven't been able to find one with any of the capacitors mentioned in several posts above. I can't rule out an LOPT containing capacitors potted within the module, but it's not easy to see what their role would be in the diode-split configuration.

Captain Proton

Sat Nov 19 2011, 01:49AM

Registered Member #3506 Joined: Sun Dec 12 2010, 02:48PM
Location:
Posts: 8

Well, I think i've managed to break the internal capacitor, at least i've got near short to the 3rd of the 3 pins (the first was the one sparking) so, now i've simply drowned the 3 pins in hot glue and will be ignoring them, which seems to leave my output unaffected ..

Yah Mary, same deal with my schematic, it only had connections for the 10 horseshoe pins, but i found this picture where you can see the inside:

20capacitor

It's not a picture of my model, but still helps give some understanding.

Patrick

Sat Nov 19 2011, 03:09AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Captain Proton wrote ...

20capacitor

It's not a picture of my model, but still helps give some understanding.

What is the silver cylinder thingie?

Ash Small

Sat Nov 19 2011, 10:35AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Patrick wrote ...

What is the silver cylinder thingie?

Capacitor?

(I did read recently that monitor flybacks have capacitors, and TV flybacks don't)

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