TV Flyback / High Voltage / Forums

Forums

4hv.org :: Forums :: High Voltage

« Previous topic | Next topic »

TV Flyback

Move Thread

LAN_403

Ryan

Sun Aug 17 2008, 05:31PM

Registered Member #1606 Joined: Fri Jul 25 2008, 02:40PM
Location:
Posts: 71

Hey, I grabbed a transformer out of a scrap tv, but im not to sure of the specs of it. Im looking to up 24v dc to 120 (approx), so I can run that into my NST for a 7500v output. Is there a way to calculate with resistance the turns ratio? Here is a picture of it. The label is one the back of the TV.

I also have this one, it came from the tv as well, will it help me out? There was a sticker on the fuse beside it that said .125a, 250v, looked like a small transformer of some kind.

Firefox

Sun Aug 17 2008, 06:14PM

Registered Member #1389 Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346

The small iron core transformer looks like a low voltage power supply, used for driving all the ICs and whatnot in the TV. My guess is that it is a 12V transformer. I do not know what you mean by running a transformer into your NST, but that flyback transformer will quite possibly give you more voltage than your NST if driven properly.

Dr. Dark Current

Sun Aug 17 2008, 06:23PM

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

The small transformer is a step-down mains frequency one, for operating low voltage electronics.

The flyback looks like your standard high-frequency color TV transformer, rated at approx. 25kV@2mA DC, 15.6kHz drive frequency. Most can be pushed to ~40-50kV and several tens of mA for short runs, they will survive but get very hot after a while when run like this. I'd say you can run it safely @30kV and some 10mA continuously. They are best to be driven around 40kHz

Antonio

Sun Aug 17 2008, 06:40PM

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

To obtain more than the usual 25 kV you have to use a driving transistor rated for more than the usual 1500 V, or to wind a new primary coil with less turns than the original.

aonomus

Sun Aug 17 2008, 06:46PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

I don't know if you have enough space between the core and the plastic casing on the flyback to squeeze in windings, but if you can, a ZVS driver would do better than using the built-in primary.

Proud Mary

Sun Aug 17 2008, 09:02PM

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

The board with the transformer on it looks very useful just as it is - a bridge rectifier with some smoothing capacitors, and a regulator of some kind probably outputing 12V DC at an amp or two. I'd hook it up to the mains (via a fuse!) and see what comes out of it.

As others have said, the flyback looks a very standard part probably outputting 20-25kV at a milliamp or two, when suitably driven.

I'm not sure what you meant about connecting the flyback to an NST, so make sure you are quite clear about what you are doing before connecting anything to the mains!

Ryan

Mon Aug 18 2008, 12:28AM

Registered Member #1606 Joined: Fri Jul 25 2008, 02:40PM
Location:
Posts: 71

About the NST/flyback thing. The I am using an input source of 24v, and I wanted to use an NST. Since the NST is rated for 120 input, 7500 output, it should do the trick for my coil, however if I used 24v input instead of 120, the output of the NST would signitifcantly lower. I was thinking of using the flyback as a step up transformer to take the 24v power and up it to 120, so that I could continue to get 7500v output from the NST. But if it puts out 20-25k volts, i dont need an NST at all i suppose.

These transformers arn't gfi'd or anythign right?

Arcstarter

Mon Aug 18 2008, 01:07AM

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

Ryan wrote ...

These transformers arn't gfi'd or anythign right?

No, but they are rectified, which is needed for tesla coils and CW multipliers. To find a suitable primary if you haven't enough room to wind your own on the core, just get an ohmmeter and connect it to each pin, and the ones with an ohm or two are your primary. Try each different winding that has a couple of ohms as the primary and the one with best output is the best primary for you.

Antonio

Mon Aug 18 2008, 02:28AM

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

Ryan wrote ...

About the NST/flyback thing. The I am using an input source of 24v, and I wanted to use an NST. Since the NST is rated for 120 input, 7500 output, it should do the trick for my coil, however if I used 24v input instead of 120, the output of the NST would signitifcantly lower. I was thinking of using the flyback as a step up transformer to take the 24v power and up it to 120, so that I could continue to get 7500v output from the NST. But if it puts out 20-25k volts, i dont need an NST at all i suppose.

Note that the functions of a flyback transformer and a NST are completely different. The 120 V input of the NST is AC, 60 Hz (just plug it to the wall) , while the flyback transformer operates from switched DC and requires an adequate driver circuit. It's completely impossible to use one as step up transformer at 60 Hz, since they are designed to operate at several kHz, and usually have an internal rectifier.

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob