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Flyback issues... I THINK

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twist2b

Tue Apr 21 2009, 02:51AM

Registered Member #2086 Joined: Tue Apr 21 2009, 02:33AM
Location:
Posts: 117

I am wiring this schematic:

And I will have the sound modulation:

I got my flyback brand new, as a "replacement part" from ebay...

I KNOW I have the circuit wired correctly, however,
I am using THIS schematic to power the circuit (using the top part)

I am getting the right voltages, and it SEEMS to go smooth, however, the flyback is un-responsive, and I don't get ANY voltage on the secondary winding..

I removed the 2n3055 for full power BTW.
I am just a little frustrated because I have been working on tihs FOREVER (it feels) and the project is due May 1st.

I know I can get it done, I just was hoping to have more fun before hand.

One thing I did get wrong was a capacitor I had it as a polar electrolytic, when it was supposed to be bi-directional.... It exploded! Funny/Scary experience!! :P I just bought a replacement and I should have it soon, but I have a feeling thats not the problem... or ONLY problem.

I appreciate any help :)

Proud Mary

Tue Apr 21 2009, 02:58AM

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

Can you put up some pictures of the flyback, lad? Just to check you have the right sort.

twist2b

Tue Apr 21 2009, 03:17AM

Registered Member #2086 Joined: Tue Apr 21 2009, 02:33AM
Location:
Posts: 117

Oh ya sure:

The blue wire is me winding it, I also just considered the fact I might have put to many windings on the flyback, but I don't know how sensitive flybacks are on that subject :P

I know that you can't tell if its having trouble via heat, because its very insulated... however, when NO voltage is flowing through, obviously there is a problem, right?

Mads Barnkob

Tue Apr 21 2009, 06:36AM

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

Have you tried switching the phasing of the primary coil? switch the leads around.

Proud Mary

Tue Apr 21 2009, 07:40AM

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

twist2b wrote ...

I know that you can't tell if its having trouble via heat, because its very insulated... however, when NO voltage is flowing through, obviously there is a problem, right?

This is the circuit diagram of a simple DC flyback, to give you some idea of how the diodes in the split secondary system are connected together, and how this relates to the screen and focus potential divider outputs - these are the two other wires you always find coming from DC flybacks.

DC Flybacks often contain many auto-transformer-mode primary taps, and additional secondaries to supply other parts of the set. I have chosen this one for you because it is fairly uncomplicated, and the additional auto-transformer and secondary voltages are clearly marked

Dr. Dark Current

Tue Apr 21 2009, 07:52AM

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

Are you getting output from the TL494 and the TC4429 gate driver?

twist2b

Tue Apr 21 2009, 05:02PM

Registered Member #2086 Joined: Tue Apr 21 2009, 02:33AM
Location:
Posts: 117

MadsKaizer - True, I have thought about that, however, I just recently found out that I might not be connecting to the right pin at the bottom... that only ONE of the pins is actually an active minus. Which means, if the circuit is wired correctly, I should just search for it with a prob (carefully :P )

Harry - WOW, flybacks are WAY more complicated then I relized. I thought they where similar to there relative, "Mr. Mains" However I was fully mistaken.. I have not been able to find such good schimatics before. THanks. :) I will look this over thuroughly. One great thing about this project is how much I have learned :D

Dr. Kilovolt - True, before the 2.2uF capacitor blew up, I was getting the readings I was hoping for :)

Something AWESOMe I found recently:

It explains ways to troubleshoot the flyback.
I wish finding information on flybacks was not so much of a hassle!

Thanks for all the help so far guys, I am going to give it another shot and tell you guys my results tonight.

Antonio

Tue Apr 21 2009, 05:53PM

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

This circuit is quite complicated, with lots of things that can go wrong and that must be checked BEFORE you power everything up. Specially if you already exploded a capacitor. Verify, with the flyback disconnected, if the DC supplies are correct, if the TL494 is generating signals, and if the signals are present at both sides of the primary coil. Before connecting the flyback to the circuit, identify the ground pin, and connect it to actual ground. The ground pins of the potentiometers must be grounded too. A floating ground in these circuits is almost sure disaster. This transformer probably has an internal capacitor. Its ground pin must be grounded or insulated.

twist2b

Tue Apr 21 2009, 09:05PM

Registered Member #2086 Joined: Tue Apr 21 2009, 02:33AM
Location:
Posts: 117

Ok, so I have to actually ground my flyback too? I did not know this... But I have no idea which one is ground.

The reason the capacitor exploded was because it was a POLAR electrolytic instead of bi-directional :P I did not notice this until too late o_O

Something weird:
I am NOT getting ANY ohm reading from my H.V. and pin 8/11
I have tried EVERY pin/wire... I get no ohm readins except a few pins interact with each other.... 1 ohms worth (no power at this time)

According to this, I can tell if the capacitor is the issue, however, I am getting no reading with the H.V. and ayhting soooooo

Argh -_-
Help?
I love toubleshooting this on my own, but it seems I can't figure this out without some help...

Dr. Dark Current

Tue Apr 21 2009, 09:25PM

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

Connect the GND of any >20V DC supply to the HVout lead, connect the positive rail of your PSU to one probe of a multimeter and prod with the other probe around the base pins; the one which gives the highest voltage reading is your HV ground pin.

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