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Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
Nah you're getting close. Look up the details from the transistors you pull off of there, and one will be suitable for driving the flyback.
I'm not sure if the blowtorch method is documented, but it works well for me. Just make sure you do it outside, burning PCB is not something you want to breath in.
For the 3055 circuit, you have no choice but to wind your own primary. If the ferrite core is not exposed on your flyback, you'll have to use the 555 circuit on the internal primary.
Registered Member #3075
Joined: Fri Aug 06 2010, 02:44PM
Location: Athens, GA
Posts: 148
Got it...so what specs or range am I looking for in the details of the transistors to know if it will work in this application?
Got a Radio shack nearby...going to go there at lunch and pick up a couple of 555's and see what else I may need...
the two resistors on that circuit...the 27Ohm 2watt and the 220 Ohm 1/2watt...those pretty common (as in, am I likely to find some on that CRT board or in the DirecTV box)?
Registered Member #16
Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554
Personally, for a first attempt, I'd say the very best flyback circuit is probably still the single transistor Powerlabs driver:
Will it give you the very best bang possible from your flyback? No. Will it work every time without cooking silicon faster than Emeril can fry an egg? Yes. The 555 based drivers are famous for killing 555s every few minutes of operation. Few simple 555 based designs have really dealt with that issue properly.
That single transistor design calls for a 2N3055, which will work with beefy heatsink. There are better transistors out there for it, but for a first crack with a small flyback, I think it will be fine.
HM Murdock, the flyback like the sort from that monitor are a real PITA to work with, and give limited results. For a really great output, you should cruise the dumpsters and thrift stores for the biggest, oldest console TV you can find (Major bonus points if it's Black & White). As a bonus, those old TVs are just loaded to the gills with great bits to scrounge.
Registered Member #3075
Joined: Fri Aug 06 2010, 02:44PM
Location: Athens, GA
Posts: 148
Thanks Dave, that is a great link! I am a very visual person, so the pics there showing the real-world parts wired in with the diagram for comparison are extremely helpful to me..
I like the design too (simple is good right now)...I am thinking I should be able to scrounge what I need for that with existing parts.
How important is it to get the resitors at the correct rating? That one calls for 270 ohms 1watt and a 240 ohms 5watt...are these specs due to what that particular transistor (2N3055) requires?
If I can get the transistor from the monitor board, how do I know what resistors to use?
also, in the meantime, can I use the FBT I have and just rely on it's built-in primary and secondary? I am NOT looking for optimal output on this first go-round...I just want to build a working circuit that makes some sparks without killing myself. Will work on making it bigger and better afterwards (projects #2, 3, etc...)
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things I have laying around...
