Mining stuff from an old TV – Flyback Driver

by Stephen Hobley on November 21, 2010

In my (now) continuing series on making stuff out of an old TV I wanted to show you next step I took.

Having tested the driver I made in an earlier post with a 12v battery it became apparent that I needed to create a much higher DC power source. Luckily I had a variable transformer and so I just needed to add a full bridge rectifier and some smoothing caps (again taken from the old TV I bought from Goodwill).

The full wave rectifier is a simple design taken from the Naudin page – I had to buy the 2N3055 power transistor from Radio Shack, but since I had the variable transformer I decided that it wasn’t needed.

The light bulb was put in series with the AC input to limit the current being fed into the circuit – please note that light bulbs only function as resistors when they are “hot” so there will always be an inrush of current at the start of any test. Ramping the voltage up slowly through the variable transformer helps with this.

Whenever I test anything like this I like to start with a 25W (25W/120V = 0.208 Amps) bulb and work up.


{ 4 comments… read them below or add one }

Tunde olaniran April 29, 2011 at 1:49 am

Pls, i need your help. I am currently working on very high voltage multiplier from 230acv to 150kdcv. I have gotten flyback but i don’t have knowledge of high voltage multiplier. Pls what is potting ?

Stephen Hobley April 29, 2011 at 9:09 am

I suggest you join and ask there, they should be able to help you create the supply you need. I don’t think I’ve ever gone that far for a DC supply. If it’s AC then I would tell you to build a Tesla coil. The best suggestion is to get a pole pig transformer and find a way to rectify it – not easy at all.

Potting is where you immerse a component in something (like tar, wax or mineral oil) that has a greater resistance to electrical energy flow than air. Older neon sign transformers use tar, and a lot of “pole pig” transformers use liquid oil.

Olaniran Badiru Babatunde August 10, 2011 at 8:16 pm

I bought some high voltage chinese diodes and capacitors for high voltage multiplier. I discovered some of these diodes were destroyed due to capacitors rapid discharge. What i can i do protect the diodes from this occcurence?

Stephen Hobley August 10, 2011 at 8:35 pm

If too much current is flowing during discharge then I would consider adding some high power resistors to reduce the current flow…

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