Need help with flyback transformer inverter

[Preher TV]

Thank you for actually trying to help.

I know the HV winding and primary windings are good, I pulled the flyback from a Envision EN-980e Monitor that ran quite well, with no issues. It is one of the newer type, with all the windings and the HV diode cast in some sort of yellowish acrylic. I located the HV return, and using a simple 12vdc supply I have been able to produce arcs of only a couple millimeters.

I have no clue what a ring test is, but if you were to explain it to me, I'm sure I could perform one.

There is a sticker on the base of the flyback that reads "SAMPO", followed by several number-letter combinations. I'll be happy to post them if they are of any help.

Well after reading through the link to the project you are doing, I see it does not matter if the primary coil is good, you need to wind your own center tapped primary and feedback coils anyways, you only need the HV secondary winding to be good.


A ring test is when you apply a fast pulse through a high Q coil , and then measure the decaying AC voltage that is induced by the pulse through the coil, each cycle of the decaying AC voltage is called a ring, the more rings the higher the Q of the coil. Q is the inductive reactance of the coil devided by it's series resistance. If turns in the coil short together, the coil effectively becomes a smaller coil with less turns reducing it inductive reactance and therefore reducing Q,as you can see putting a resistor in series with a coil will also reduce Q this is called a de-Quing or damping resistor.

your concern is obviously with windings that shorted together reducing Q. You can buy a simple tester that will do a ring test.They cost at minimum $100 for a simple FBT, unless you buy a kit to assemble one.You could also build a ring tester yourself schematics are available.But it sounds like you are sure your Flyback is good.


If you are not happy with the size of your sparks, you may want to use a bigger Fyback transformer say from a 32" TV intead of a 19" PC monitor.

 

[Rey]

Wasn't really willing to spend $100 on this project, but anyways, how can I go about solving this issue with the low resistance? I doubt that the HV windings would have anything to do with it.

 

[Preher TV]

Wasn't really willing to spend $100 on this project, but anyways, how can I go about solving this issue with the low resistance? I doubt that the HV windings would have anything to do with it.

No the HV winding is not causing the low resistance reading across Vcc . I would double check your circuit again and the value and position of all the components. Just because you get a little sparking does not mean it's wired properly.

 

[Preher TV]

can you upload some pictures of your circuit.....

 

[tcmtech]

This is the same circuit I used and still often use for HV flyback type drivers.
The one I used in high school just used four turns of 14 gauge wire for each half of the primary coil and was wound on the core at the opposite end from the main HV end.
I used a pair of high gain Darlington transistors and a 12 volt battery as the power source. C1 is used to tune the resonance point of the coil.

Even with small computer monitor flyback coils this circuit when tuned right will still cover the outside of the HV coil assembly with a noticeable corona discharge and can shoot a corona discharge flame right off the HV wire end itself into thin air. I have made larger ones from old TV flybacks that could draw out an arc to around 3 inches and produce a corona discharge about a 1/2 inch thick off of the coil body itself. But large switching devices and a fair amount of power are needed at that point.

The more modern version uses a higher resistance for R1 and R2 and a set of IGBT's or Mosfets. A clamping zener across the gate to emitter or source is recommended though when using voltage controlled switching devices in order to keep from over voltaging the gate itself.

 

[Rey]

Thanks a lot for that, I will try that schematic tomorrow. What wattage do you recommend for the resistors?

And off topic, when you say corona discharge, are you talking about ionized air? I have a small device that I pulled from an air purifier, that produces maybe 3 or 4 thousand volts, through what I presume to be a voltage multiplier. Attaching it to a large piece of metal results in a large mass of ionized air, causing a minor electrocution if you touch any metal objects nearby. Quite fun for pulling pranks.

 

[tcmtech]

The resistance and the wattage will depend on what type of switching device you are using. For transistors I tried to go for about 80% of maximum base current at a 2x input voltage.

The natural resonance of most fly back transformers is around 25 - 50 KHz so expect some fine tuning to be needed with C1. It can be left out but the circuit will drift its frequency far more as the input voltage and load changes.

Corona discharge is that purple/white static fuzz that HV AC generates.

 

[Preher TV]

Corona Discharge

Plasma