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HM_Murdock

Thu Aug 19 2010, 06:15PM

Registered Member #3075 Joined: Fri Aug 06 2010, 02:44PM
Location: Athens, GA
Posts: 148

I am going to be re-trying to wind my own primary on my flyback for the push-pull 2n3055 and then a ZVS, and would like some clarification here...

1) Do I need to use magnet wire, or will solid core insulated wire (like from Home Depot) work as well?

2) I know the primary and feedback coils have to run in the same direction, but do they have to also match the secondary winding? If so, how can I tell which direction the secondary is wound?

3) is there a particular gauge combination that works with certain voltages, or is it more depending on the circuit? (or is it not that important?)

4) can bare copper wire be used in combination with electrical tape in a manner such as a layer of tape on the core, and a layer of tape over each separate coil?

Plasmana

Thu Aug 19 2010, 06:59PM

Registered Member #3108 Joined: Thu Aug 12 2010, 05:37PM
Location: Worthing, England
Posts: 72

Ill do my best to answer those questions.

1) Any insulated solid core wire will do, preferably copper. Magnet wire just lets you wind things more tightly, without all that chunky insulation taking up space.

2) I don't think there is a way to tell if the secondary is encase in epoxy. The best thing you can do is switch the primary and feedback around and see witch configuration works the best.

3) It is more depending how much current you are going to put through it. Nice thick wires for high current and thin wire for signal current.

4) I never used bare wire and tape when winding onto things, it is just a pain to use this technique. It will work, it may be a pain to get right.

I hope this helps and please don't take all my answers seriously, they may not be correct, they are all from my experience.

HM_Murdock

Fri Aug 20 2010, 01:37AM

Registered Member #3075 Joined: Fri Aug 06 2010, 02:44PM
Location: Athens, GA
Posts: 148

well, this is odd...

I tried winding my primary with 14AWG copper (solid core) insulated wire. Went 8 turns to try it to start, and it didn't work. Tried reversing my polarity, no good. Tried re-winding in the opposite direction, and both polarities again...nothing.

So, I try hooking it back up to my built-in primary pins, and again, nothing. Leave everything in place, and replace the 2n3055, and it works on the built-in pins. Hooked back up my newly wound primary, and nothing. Switched back to the built in, nothing.

Bottom line, 2 transistors fried, and best I can tell it was due to hooking up my self wound primary. I tested my setup prior to disconnecting the flyback to wind it, so I know my first transistor was working to start with. I hooked up my 3rd (and last) 2n3055, and it works on the built-in primary again...but I need to figure out what blew the first two before I can move on . Would having 8 turns on the primary do this, or am I doing something else wrong?

Any ideas?

radiotech

Fri Aug 20 2010, 06:08AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

Bottom line, 2 transistors fried, any ideas?

You might try to test the fried transistors to see how they failed
using your multimeter.

Slowly increase the voltage to the circuit.
Then limit the current from your power supply using a small lightbulb sized to just glow dimly if the circuit works or brightly if it sees a dead short circuit,

2n3055s are most easily blown by Vcc B-E.

Xplorer

Fri Aug 20 2010, 09:14AM

Registered Member #2416 Joined: Sun Oct 04 2009, 04:23AM
Location: Oceanside, CA
Posts: 91

I've read you shouldn't use 2N3055s because the primary can create voltage spikes that will feedback into the transistors and fry them.

-Tony

teravolt

Fri Aug 20 2010, 07:35PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

Hi HM, make shure that the bases are wire correctly. sometimes the oscillator won't start up if the bases are not conneced to the proper feadback winding

Osama Ma'mon

Sat Aug 28 2010, 06:27AM

Registered Member #3144 Joined: Fri Aug 27 2010, 01:44PM
Location: Egypt
Posts: 16

what is the turn ratio of a standerd flyback transformer

zhgart

Wed Sept 01 2010, 07:46AM

Registered Member #3156 Joined: Wed Sept 01 2010, 02:19AM
Location:
Posts: 4

I'm afraid that pic is not a flyback transformer.
just a pullpush circuit.
turn ration shuld be >=1:1000

Antonio

Wed Sept 01 2010, 01:06PM

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

Never assemble a circuit and simply power it on without checking everything. Follow the advice about the lamp above if everything seems right. Anyway that simple oscillator with a 3055 transistor never lasts more than seconds at high power, unless carefully optimized and with protections for the transistor added. Probably invented by 3055 manufacturers...

Matt Edwards

Wed Sept 01 2010, 11:06PM

Registered Member #2838 Joined: Fri Apr 30 2010, 07:55PM
Location: tehachapi, CA
Posts: 333

Without being able to fine tune the circuit you will likely just keep killing the 2N3055's. They get hot vary quickly and die. I have seen some people use them successfully but I personally would just save some time and money and try another transistor. I have had vary little luck with them.

There is a good list on this page near the bottom.

I have tested several of the transistors listed and found similar results. I have also had good luck with the NTE379 and they are fairly cheap.

Even though it is a lot of extra work, you will likely be much happier with the output of the mazilli zvs circuit. FYI save a step and build the second one with 100R resistors between the primary and feedback. It seems to produce much better results.

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