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Registered Member #1389
Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346
I recently tore apart a scanner, not knowing what I would find, and found that the step up boards used to drive the scanning lights. While playing around with one plugged into a wall wart (15V @ 400mA) I managed to draw 4-8mm hot purple flyback-like arcs from the positive lead (it seems to be halfwave AC) to an ungrounded metal object (insulated from me of course). A hobby knife works quite well. Arcs to the ground side of the board were considerably less fantastic, if existent at all. Having seen the simplicity of the circuit, I have decided that I want to replicate it, only with higher voltage/amperage parts (especially the transistors). I would also like to modify it for full wave AC, but I really don't care too much about the waveform, I do intend to use it to drive CW multipliers, as the board from the scanner drives a 5 stage half-wave max 1kV @ 1A CW quite nicely. IIRC, square wave high freq. is ideal for this. Here is the schematic I could come up with.
(sorry about MSPaint, I dont have anything better)
I have three problems: 1. I cannot find the datasheet for the D1616A transistors on the board, though I believe that they are NPN BJTs. This also means that without knowing how the circuit works, I don't know which pins are which. They are the circles in the schematic. 2. I have no clue how the transformer coils are situated save for the fact that it is an 8 pin transformer. 3. Even if I did have all of the above info, I don't know enough about circuit design to properly modify it to give me full wave AC.
I can get pictures of the board itself if I really need too, but right now my cameras are out of commission.
Registered Member #1132
Joined: Mon Nov 19 2007, 06:15PM
Location: Slovenia
Posts: 84
I played around with a simalar cirucit. And it dosent shock since thre freqency is high enugh but directyl arcing to your finger will hurt cause the arc is hot.
As for getting more power out of this thing its not a good idea. I tryed replaceing the transistors with beefyer TO-220 and more input voltage. The transformer arced over quickly and bye bye.
So yeah dont try to get more power since you will only break it.
Registered Member #1157
Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307
Firefox wrote ...
1. I cannot find the datasheet for the D1616A transistors on the board, though I believe that they are NPN BJTs. This also means that without knowing how the circuit works, I don't know which pins are which. They are the circles in the schematic.
Registered Member #1389
Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346
Thanks for the datasheet Ultra7.
I intend to build a beefier setup in general, berni, by replicating the whole board with higher power parts, but first I need to figure out what kind of transformer this is and how it is wired.
Registered Member #1132
Joined: Mon Nov 19 2007, 06:15PM
Location: Slovenia
Posts: 84
The cold cathode inverter i was toying with was built on the same principal as those single trasistor flyback drivers, but with two trasistors for the positive and negative half.
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