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Very old Flyback

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LoFi Ninja

Fri Mar 13 2009, 02:59PM

Registered Member #2024 Joined: Fri Mar 13 2009, 02:08PM
Location:
Posts: 5

Hello..

I've got this old flyback

3350810935 19a2bd65df M

So ofcause I want to play with it!
In the second pic you can see two coils.. Whats the very small one ? feedback?

Anyways I wish to use this simple driver I found on SIXMHZ site http://www.angelfire.com/80s/sixmhz/flyback.html Will it do?

Arcstarter

Fri Mar 13 2009, 03:37PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

It will work, yes. But it will be very low power and lots of heat. The ZVS is however not suggested to beginners of high voltage, they can likely kill. The 555 flyback driver is something i would suggest, to keep heat down and get higher efficiency. Also, if you make it well and use higher input voltage, you can get very high voltage. I have had sparks jump 8 or so inches!

With the 555 driver, you can also make it sing, by simply putting an audio signal into pin 5. More on that if you get one built (on my spare time, i like to pretend i am a news reporter, or someone that matters

)

Proud Mary

Fri Mar 13 2009, 03:59PM

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

You are lucky to have found an old AC Line Output Transformer (US: "flyback") which does not have rectifiers built into the case, and so is much more valuable to the experimenter.

The small inductance wound on the core in your second picture is not a feedback winding. It is the filament supply for the rectifier valve (US: "tube") that would have provided (typically) 6.3V @ 100mA or so, depending on the particular rectifier valve designed for.

The open frame construction of this kind of LOPT makes it very easy for you to wind your own primary, as many on this site prefer to do.

A lucky find!

LoFi Ninja

Fri Mar 13 2009, 04:18PM

Registered Member #2024 Joined: Fri Mar 13 2009, 02:08PM
Location:
Posts: 5

Arcstarter: Ok I will go for a 555 driver.. I surely want it to sing ! I guess some 8-bit chiptunes fits nicely hehe..

Harry: Yes I know it's a nice one.. I've tried earlier with the newer black pottet ones and never made it work. And Have read many times how you would want an old one with a bare primary, and no rectifiers.. I have actualy had this guy for like a year two in a drawer, because I kind of abandoned HV because I never could get stuff to work, but I still could't throw it.. I guess I knew I wanted to try again some time haha..

Anyways, so I can just remove the small coil underneath the primary ?

PS: Why do people want to wind primary them selves? For fine tuning?

PPS: I also have a cascade that I found with this flyback.. So in theory I should be able to get around 25 KV yes?

Proud Mary

Fri Mar 13 2009, 05:16PM

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

LoFi Ninja wrote ...

Anyways, so I can just remove the small coil underneath the primary ?

Yes - the filament heater winding is unlikely to be of use to you.

LoFi Ninja wrote ...

PS: Why do people want to wind primary them selves? For fine tuning?

The LOPT's own primary coil is designed (from memory) to work at about 115V, and has a good number of turns on it. Some experimenters do use the original primary, but most prefer to wind a primary with far fewer turns on the core, to drive it with NPN bipolar transistors like 2N3055, or the more fashionable power mosfets with very low on resistances.

LoFi Ninja wrote ...

PPS: I also have a cascade that I found with this flyback.. So in theory I should be able to get around 25 KV yes?

Yes, that sounds possible.

Littlew

Fri Mar 13 2009, 06:29PM

Registered Member #1448 Joined: Sat Apr 19 2008, 01:16PM
Location: Russia/Moscow
Posts: 21

put something to compare sizes(box of matches etc)
i thought it is rare 25kV flyback(my opinion is based on construction of flyback)

LoFi Ninja

Fri Mar 13 2009, 07:02PM

Registered Member #2024 Joined: Fri Mar 13 2009, 02:08PM
Location:
Posts: 5

No noo.. Usually flybacks are what ? 8 kV? And then the cascade multiplys by 4 so thats 32 kV but that's aiming really high.. So 25 kV..

LoFi Ninja

Fri Mar 13 2009, 08:56PM

Registered Member #2024 Joined: Fri Mar 13 2009, 02:08PM
Location:
Posts: 5

Would it be a problem replacing the MOSFETwith a IRF634A in this schema ?Allthou the RDS(ON) is 0,45 ohm ? and not as low as 0,1 ohm..

ET Flyback Basic

Proud Mary

Fri Mar 13 2009, 11:28PM

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

Perhaps you should put a buffer between the timer and the gate.

I would be concerned that without any protection, that a 200V mosfet may not long withstand inductive kick-back spikes.

You will find plenty of comment on these subjects if you search the forum for them.

Dr. Dark Current

Sat Mar 14 2009, 09:18AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

With 12 volts he will be absolutely fine with a 200V FET.
The problem is that this circuit heats a lot, and if you use a bipolar transistor it heats even more.

An improvement is my "quasi resonant" mod. (search forum)

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