Very old flyback

[Alberto]

Hi everyone.

I got this flyback



But I have measured the resistance between pins and I get very low values . All values are in ohms

BC 0,7
BD 1
CD 0,3
EF 2
GH 0,2
GI 0,1
GJ 0,1
GK 0,1
HI <0,1
HJ 0,1
HK 0,1
IJ 0,1
IK 0,1
JK <0,1
LM <0,1

Pin A doesn´t combine with any other, event the armature. But near the cable there are some cbales like  broken? But I think they aren´t from A testing with the DMM. You can see that in this photo



Are normal this values?

The thinest wires go to E and F, but it´s only 2 ohms. Are they supposed to be the HV output?

Pin A are 3 thin wires braided

I prefer ask you first, because you know a lot about these things, and I think this kind of flybacks are difficult to find.

Kind regards.

[davekni]

There would have been some high-voltage lead exiting from the outside diameter of the largest winding, likely from the middle to keep it away from both the core and other winding terminals.  I'd guess that this lead has broken off.  A may be the inside end of the high-voltage winding.

[Alberto]

There would have been some high-voltage lead exiting from the outside diameter of the largest winding, likely from the middle to keep it away from both the core and other winding terminals.  I'd guess that this lead has broken off.  A may be the inside end of the high-voltage winding.

You were right!! Thank you very much.

It has been veeeery difficult, but I have managed to find the broken wire scraching the cover. It was very short, and the cleasing and soldering was a nightmare, but I fixed it! I think I deserve a engineering degree for that 



The tape is provisional while the polyurethane dries.

[davekni]

Glad to hear you found the broken wire end.  The fine wire of HV windings can be tricky to handle without breaking.  I haven't personally dealt with any flyback transformers that old.

[MRMILSTAR]

If your working with very old flybacks, I imagine it must be because they have AC output. New AC flybacks are available on E-Bay and you don't have to deal with cracked insulation and broken wires as you often must with NOS flybacks. Do a search on E-Bay for "flyback F0239". I am using 2 of these to power a CW generator that I am building. They are only $29 or best offer. I bought 2 for $50.

[davekni]

Steve,  Have you found any specifications for this F0239 flyback?  Have you measured any parameters?  It looks interesting, but I can't find any information to know how useful it may be.

[Alberto]

No no, I went to a scrapyard to see what I could find on electronics. You really can find great teasures. But this time I only found this very old TV PCB and 9 very big capacitors.

I dind´t have anything in mind about the flyback. it´s only I love to collect old electronics.



They are merlin gerin varplus m1. 68 uf and I have no idea about the voltage but they look valuable.

everithing cost 5€ (Some PCB with interesting components too)

[MRMILSTAR]

Dave,

I haven't found any specs on the F0239 flyback but I did make a few measurements the other day. Its also made in Taiwan so it may be higher quality than one made in mainland China. My CW multiplier power supply consists of two of these F0239 AC flybacks in parallel. Each flyback is wound with 11 turns of 14 AWG THHN wire on the ferrite core open leg as the new primary coil. The ZVS driver is one of those Chinese models with 6 of the 0.33 uf MKP capacitors in parallel. The low voltage power supply is an adjustable SMPS capable of supplying 300 watts. I did remove all of the pins from each flyback except the HV return pin. I filled the void with paraffin to cover up the unused factory primary coil wires just for extra corona mitigation.

I measured the resistance of the flyback secondary coil as about 1100 ohms. I can't determine the diameter of the HV wire but its quite small. If someone knows the typical gauge of these wires, then it may be possible to determine the approximate number of turns in the secondary coil from the resistance.

For voltage measurement I made a HV full wave bridge rectifier with fast diodes and a 2 nf smoothing capacitor. This rectifier was attached to the flyback HV output. The load was just a 25 megaohm 30 KV Caddock HV resistor that I had on hand. I haven't yet finished the rest of the multiplier so this was my test load. The DC output of the full wave rectifier was measured with a HV DC probe with integral voltmeter.

The results were as follows:

ZVS driver DC input voltage from SMPS        DC output voltage from full wave bridge rectifier with load
-------------------------------------------------         -------------------------------------------------------------------------
                        18                                                                            14 KV
                        17                                                                            13 KV
                        16                                                                            12 KV

So 14 KV DC should correspond approximately to the peak of the AC sine wave resulting in 9.9 KV RMS AC assuming my ripple voltage is zero on the rectifier output, which of coarse it isn't but its close enough. The resonant frequency of the flyback primary circuit was measured as 30 khz with an oscilloscope.

My CW multiplier design requires a 14 KV peak AC input voltage as input to the multiplier stack, so an 18 volt DC power supply will be perfect for my application. Granted I was only supplying about a 8 watt load with the HV resistor that I had on hand so there may be a little droop when I connect it to the actual multiplier stack. If so I may have to increase the DC input voltage slightly from 18 volts. I don't know how much power I can get out of these flybacks. They appear to be fairly large. I am hoping for at least 200 watts for the two in parallel at least for short periods. 30 khz should be an acceptable charging  frequency for the multiplier stack.

In conclusion it appears that these AC flybacks are going to to do the job for me. I have 2 gallons of mineral oil on order. When I receive that I can fill up the multiplier stack and try it out. I should have this CW multiplier finisihed in about one week assuming nothing fries. I will post results when I am done.

One other point is this. I initially just supplied 24 volts DC with 2 lead-acid batteries in series. I made no measurements but it produced a very satisfying arc. If the relationship is linear from my other measurements with the rectifier, then the output was approximately 18.7 KV DC or 13.2 KV AC RMS.

[davekni]

Steve,  Thank you for the measurement info!  I may get one to play with and as a backup for my little plasma globe.

[Alberto]

Ops, the photo was wrong. These are the capacitors

[John123]

Oh that's a nice find! Careful not to run it at its resonant frequency unloaded or else it will arc over!

[Alberto]

Oh that's a nice find! Careful not to run it at its resonant frequency unloaded or else it will arc over!

What do you mean? Arcing between coils? I have run it with an 555 oscillator with 8 turns in as a primary with 12V and the arc between HV pins starts at 5 or 6 mm. But I didn´t see anything inside the coils nor sound of arcing.

Nevertheles I´ll be carefull in the future.

But yes, it was a nice (And cheap) find.

[John123]

Oh I meant running it on something like a bridge driver which people often do with these AC flybacks, if you hit the right frequency when tuning the frequency pot it'll suddenly give out lots of voltage a bit like a tesla coil and arc over and burn the insulation unless you put a safety spark gap in there.

Might be able to get something similar going on your 555 timer driver by putting a resonant capacitor of about 220nF across the primary coil and sweeping the frequency to find the sweet spot, although I've never had such destructive arcs with the 555 timer.

Notice how the arcs just want to keep growing in this video? Without that gap the HV would destroy the transformer.

Was just trying to give you a heads up since it would be a shame to destroy such a nice LOPT, they certainly aren't getting any easier to find.

[Alberto]

Ok ok thank for the advice!

I´ll try the thing with the bridge driver, but with a regular and cheap modern flyback.

I don´t think I´m going to use this one for anything, as you say is a nice LOPT and I can have btter results with the ones taht MRMILSTAR said.

I fixed it because I like to have things in good conditions.

It´s a good moment to remind you I don´t speak english, so sorry if I make mistakes.