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Flyback Pinout Confusion

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LAN_403

Meatball

Sat Oct 03 2009, 09:14PM

Registered Member #2401 Joined: Mon Sept 28 2009, 04:25PM
Location:
Posts: 74

I've been reading multiple websites along with the forum, trying to find the HV return pin of my flyback. I have some confusing results... unfortunately.

I have a Sanyo TV replacement part flyback. Its an older part that never got used, and so i was able to buy it for $5 from a local repair shop.

It has a secondary that is just over 2 inches in diameter and about 1 inch in coil length. The iron core leaves me plenty of space to wind a new primary and feedack. So anyways..

According to several websites and posts here on the forum, the resistance of the HV coil is supposedly huge... in Mega Ohms. Something impossible to measure with a halfway normal multimeter. However, when attempting to execute the many suggested processes for finding the HV return pin, I have come up with nothing. I've tested all the pins for continuity between each other and have found two coils total. One coil is between three pins. The coil is 1.0 ohm which is center tapped. The other coil between 3 pins in 2.0 ohms, but one tap is 2ohms, and the other is a half ohm. This greatly confuses me.

Whats worse, when I as checking pins for continuity with my HV out pigtail, I found that the pin between the other two coils has 697 ohms of resistance of continuity to my HV out.

So do I have a HV coil with a very low impedence? Or is something else wrong? Did I test it incorrectly? Is there something more I can do to find out for sure, which pin is my HV return?

Lastly, after further examination of the wires that leave the pins, and go in to the epoxy/resin, I noticed that the suspect pin with 697 ohms was the only one that had wire without an insulator around it. It is the only wire that goes bare, and uncovered as it goies into the resin. Does this indicate something? I was hoping it could help as a clue.

Thank you for reading about my concerns, I would greatly appreciate anyone's assistance in getting this pin identified.

-Tyler

Proud Mary

Sat Oct 03 2009, 09:19PM

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

Meatball wrote ...

Thank you for reading about my concerns, I would greatly appreciate anyone's assistance in getting this pin identified.

-Tyler

Tyler Durden here too?

TV designers try to get as many HV outputs from LOPTs as they can to drive circuits in other parts of the television.
These often take the form of auto transformer taps on the primary. Medium voltage (100V - 200V) supplementary secondaries, as well as the EHT winding in which you are interested.

If you'd like to give me ALL the numbers written on the shell, I'll see if I can find the data sheet for you in HR Diemen's "The Book" but it looks like a vintage AC type, so I wouldn't hold out too much hope,

best wishes,

Harry.

Antonio

Sat Oct 03 2009, 09:35PM

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

The "huge resistance" of the HV coil reported (erroneously) in some sites is due to the high-voltage diode in series with the coil. Your coil probably does not have a diode, and the 697 Ohms are the resistance of the coil. The pin where you measure this is the ground terminal. The other two windings are the primary coil (to use it you must drive the coil with a quite high voltage, but as compensation with quite low current). and a feedback coil, that you can use to obtain a scaled down version of the output voltage.

big5824

Sat Oct 03 2009, 11:31PM

Registered Member #1687 Joined: Tue Sept 09 2008, 08:47PM
Location: UK, Darlington
Posts: 240

Just wind your own primary on and power it up, the pin the lead arcs to the most is the secondary return pin :)

Mads Barnkob

Sun Oct 04 2009, 07:50AM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

I got a flyback identical with yours, there should be only one pin that have a wire go directly into the the core, the rest can be seen go to the primary windings.

Unless it already filled with varnish in the middle, which you should also do when you have identified the pins, else you will likely experience flashovers.

It has come to such an extend that even though the exposed core is pretty far from the seoncondary winding, I can drive this little sucker so hard I get flash overs from the new primary windings to the secondary body.

Dr. Dark Current

Sun Oct 04 2009, 07:51AM

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

big5824 wrote ...

Just wind your own primary on and power it up, the pin the lead arcs to the most is the secondary return pin :)

I thought he already found the return pin by measuring 697 ohms to it from the HV lead...? I have a flyback which HV coil has over 700 ohms...

I usually don't use the other pins, I wind my own primary which has many advantages.

Meatball

Fri Oct 09 2009, 09:44PM

Registered Member #2401 Joined: Mon Sept 28 2009, 04:25PM
Location:
Posts: 74

Wow well I thought I would leave my post up here for a week before checking for responses, but I got too impatient! So many helpful responses already! Thanks guys!

@Harry, The number printed on the shell is F-1108. My suspicion is that it is a Sanyo. But its ok if you can't find anything on it though!

@Mads Barnkob: You say you have one pretty similar to mine huh? How hard have you been able to safely push this guy? I was considering ~36V from a ZVS... but I'm still looking into it.

Yes, the core is already filled in with a resin of some kind.

@Dr. Kilovolt: I am planning on winding a new primary since I am leaning towards the ZVS driver as my supply. I understand that it requires ~5+5 windings... correct? I still have not been able to identify what kind of gauge would be most beneficial for the windings though. Would you have any recommendations?

Thank you all for your assistance!

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