Thread: Big Joule Theif
View Single Post
Old 11-21-2010, 04:09 PM
Vaporizer's Avatar
Vaporizer Vaporizer is offline
Join Date: Oct 2010
Posts: 58
Hi pentiger.

This is my 1st post on the forum after a month of reading, saving data, pics, videos and building a few JT's & Bedini circuits. I have a fairly diverse background and may be able to help you trouble shoot your problem. I don't want to come across as a "know it all" by any means. This area intrigues me as the 1st time I read abt it and I'm highly reluctant to accept "never", impossible", or "can't as an answer. I do wish the forum had a "Welcome" area to cover introductions for new members. To all that have experimented, posted, I cannot name all of you or thank you enough for sharing. Failed tests show as much as successful ones IMHO. I just hope to add what I can and help where I can. I love the "open source" concept.

Watching 6v tick down as seconds go by is not acceptable especially running down in 10 min. I didnt see your circuit posted so lets approach this from a strictly diagnostic/elimination of the high drain.
You disconnected the secondary and it had no effect. Actually, it shouldn't as its working on the collapsed field of the primary. Unless you are trying to feedback as in recharging. This leaves 2 possibilities from what I see.
Your circuit is drawing a tremendous amount of current or the battery cannot supply the current needed. What is your 6v source? 4AA's, a 6v lantern battery? Rechargeables? One failing battery in a string can cause the effect you are seeing. As it dies off it cannot conduct the voltage from the others. When it fails I'd measure each individual cell to see if one is greatly lower than the others. You don't mention an Amp rating for the 6v. A 9v rectangular rechargeable is abt would fall off fast compared to 4AA's rated at 2800ma.

You also need to check the current draw of the running circuit. It must be oscillating if the secondary has output. An apparent high current draw as you describe should produce heat somewhere(assuming the batteries have the current capability). The transistor or the coil would be the 2 highest suspects. If you are using a diode in the circuit, it may be in backwards allowing current to flow to ground, but the circuit still operates.
If you have a meter capable of reading voltage, you can disconnect the + lead to the circuit and put a 1ohm resistor from the battery + to the + input of the circuit. Set the meter to read low volts, start the circuit and take a reading across the 1ohm resistor. The reading in volts is the equivalent of the current draw in ma's. So, if you are reading .750vdc, that's 750ma current draw with the JT basically idling.

If you could do these tests, post the results, helping would be easier. Also a schematic of what you are building and a pic of the project will add in solving the mystery.

Hope this helps you.


Experience is what you get when you didn't get what you wanted.
Reply With Quote