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Help with photoflash capacitor charging circuit

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bobbylo

Jun 15, 2014
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I recently purchased a few Union 15A ee19 photoflash transformers from wellgain electronincs.I searched all over the internet for any data or diagrams on this transformer,theres nothing.Wellgain only has the diagram of the windings.
I wired it to a breadboard,and fried 2 transistors already.I think its wired right,but maybe the transistor,or diode or resistor is wrong.By the way,wellgain says the input is 3 to 6v.When i test the voltage coming out of the circuit i'm getting about 377volts.When i hook up a 400uf 330v capacitor,it can't seem to charge it.It charges it very slow,and nowhere near the full charge.Also,i don't hear that whinning sound the circuit usually makes....Anyone know anything about this???
Thanks in advance for your help
 

Harald Kapp

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Welcome to our forum.

It helps a lot showing us a diagram of your circuit.
 

bobbylo

Jun 15, 2014
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Hi,don't know how to do a real diagram,so i kinda drew one with with the paint program in windows xp .It is a 5 pin transformer,i'm using a 1k resistor,and 2SD882 transistor and a 1N4937 diode.I tested the ohms across the primary and get 0.3ohms,across the secondary is 3.6 ohms,and the feedback is 1.2 ohms.I'm also posting the only diagram they gave me of the windings...Thanks for the response
 

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KrisBlueNZ

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Looks exactly the same to me. What's the difference? Those circuits run at low voltage and use a transformer with a tapped secondary. Which transformer is much bigger?
 

bobbylo

Jun 15, 2014
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Looks exactly the same to me. What's the difference? Those circuits run at low voltage and use a transformer with a tapped secondary. Which transformer is much bigger?

The one i have is much bigger,its about 4 times bigger.The place i brought it from says the input voltage is 3 to 6 volts..But i'm not sure that thats the right voltage.
I don't think they even know.They have thousands of them,but they don't make them anymore.I think they were made around 1980.The ones from the deposible cameras have a very high secondary ohm reading.I was getting about 370 volts when i replaced my meter leads where the capacitor went.It charged it,but really slow.Then when i held it for about 30 seconds,the transistor fried,but i did have about 150 volts in the capacitor.....
 

KrisBlueNZ

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The size doesn't matter. That circuit should work regardless. There are much better ways to drive it though.

This page looks good. The second circuit (the "Mk II" version) is best. He is talking about driving flyback transformers from TV sets but your transformer uses the same idea. Connect your diode and capacitor to the secondary. Try it both ways round; one way you'll find you get a much higher voltage.
http://uzzors2k.4hv.org/index.php?page=flybacktransformerdrivers

There's also a design with a brief description at
http://www.eleccircuit.com/efficient-flyback-driver-circuit-by-ic-555-irf510/

There's also a design with a description on the page at http://qandasys.info/flyback-transformer/ but it's the second design, called "Car ignition coil driver". It will also work with your transformer, and there are some useful notes on the design that you should read.
 
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