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Registered Member #2563
Joined: Mon Dec 21 2009, 10:17AM
Location: Australia
Posts: 280
Gday all i have a few, well 5 HV units out of photocopiers, and two of them have snapped pcb's and i was just curious as to whether anyone here knows how the transformers operate, would they use high or low frequency, theyre iron cored. and the pcb's use 24 volts is all i know at the moment anyways, im a bit stuck on finding theyre primarys. but could i just drive them with a simple oscillator like a 555?
Registered Member #1408
Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679
I have a few myself: however I am a novice and many here will give you much more detailed information. They ARE HF but I don't have a scope. For the units to function you should have pulled the boards along with the x-formers. They are often 5kVdc The leads Black & white should be coupled: red lead the positive I have (as an example) what I believe is 12Vdc in thus you couple the blk & white (-) Red to your + supply. They also will have the standard Green stripe ground wire and the thick white "Hot" output. The little spark will be draw between the green ground & the thick white. Remember that you must couple the black & white as a DC - and red as your DC + At least this is what I have seen with quite a few. Appear Ferrite cored similar older model flyback. These appear to be small flyback appearing design and (mine) can take a DC voltage variant from 10-19 volts without any undue stress. If you know it will handle 24v then go for it. I would not go higher than 2 or 3a in current in any event. I would be careful as they may not be made to handle that much current. Generally in some copiers and laser printers you will find 2 such units with a small "flyback" appearing transformer on each. I believe that they MAY be specifically designed for a laser in certain applications and increasing the input current may strain it. Notice that either there are no heat sinks or very tiny one. These are NOT made to handle a lot of current or perhaps even time in use. The small pc board attached is the driver which in mine appears to be the most simplest of designs. Driving the unit w/ a 555 is an unknown to me as the small transformers are apparently made to work for a give short term. That being the logical design, building a driver that would allow higher current MAY result in damage to the x-former. I would examine the boards 1st. They may provide a clue as to what type of driver would best suit this transformer application; yours may be tougher. They appear to use a switching transistor and the components and traces are quite small for not being SMD. I would attempt less than 1A at first with a homemade design.
If you have the pieces of the board, you may see that a similar oscillator driver could be made by simply copying just that portion of the board. On the examples I have they have a single transistor of the TO-220 package w/ heat sinks so small that they appear to simply dissipate heat from surrounding ultra small components. They make a great little supply for testing voltage multipliers and testing high voltage probes as they have mostly .2+ ma they wont burn most things out
Registered Member #1749
Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497
I have a couple as well they aren't that great TV or monitor flybacks are as good as they come. And if they are iron cored they operate at a lower frequency than ferrite formers all the ones I have are ferrite and they operate at 24V as well are there transistors on the left over board?
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Photocopier transformers
anyways, im a bit stuck on finding theyre primarys. but could i just drive them with a simple oscillator like a 555?
