think i'm going to radio shack to pic up some new parts.

 

The transistor is a NPN type,,, some Joule Thief circuits use a BC547, so get an equivalent type.

Where are the voltage measurements we asked for?

Like to help.

__________________
Eric
"Good enough is Perfect"

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Bill's: www.blueroomelectronics.com/

 

will get you the measure ments later. my batter in my multi died. man what a day. when it rains it poors

 

where is a good place online to get components? i hate radio crap. over priced retialers. i'm in Central NY state. anything around me with quick shipping?

 

Now that you have the correct NPN transistor you can try swapping the wires from one winding around.

Is the LED connected with the correct polarity? The wire beside the flat on the case connects to 0V.

Use a new alkaline battery cell, not a lousy old "heavy duty" carbon-zinc piece of junk.

Don't solder to a battery cell. Use a battery holder.

__________________
Uncle $crooge

 

k will do. how do i test to make sure the transistor is working correctly with a meter? don't forget i'm a newbie but a very fast learner.

 

Does your meter have a transistor tester?

A simple way would be to use the diode checker, hold the + test lead on the base and check that the foward voltage reads about 0.6V to 0.7V when it's hooked up to the emitter and collector.

Failing that you can test a transistor like this.

Just make sure the LED you're using works and the battery isn't flat. Don't worry about the switch just use connect the resistor to the collector and disconnect it again, LED LED should turn on and off.

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I could be wrong, but it looks to me like you have A2 and B2 swapped. Check to see that you have 1.5 volts on the collector,, and 0.7 volts on the base.

 

mine also doesn't work... with ~1,35V battery i see ~1,33V on collector-emmiter and ~0,75V at base

i have posted photo on this thread...

http://www.electro-tech-online.com/c...ighlight=joule

 

I dont see a capacitor!!!!!!!!!!!!

__________________
MechTronics

World of Warcraft is a disease

 

me too... what? it doesn't oscillate without capacitor?

 

The Joule Thief circuit does not have a capacitor.

The base gets noise current which makes the transistor conduct a little. The collector goes low and transformer action makes the base go high which turns on the transitor fully. When the transistor reaches its peak current then the current doesn't change anymore so the transformer feed to the transistor's base drops, which causes the transistor to begin turning off and the transformer gives a negative voltage to the transistor's base which helps turn it off quickly. Then the collector voltage nearly goes twice as high as the supply voltage

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Uncle $crooge

 

Audioguru, instead of noise current, isn't the 1K base resistor sufficient to bias the transistor to conduct somehow?

The 1K resistor value is vital to circuit operation and value depends on Beta of the transistor used. If one uses other transistors and the circuit does not work, be sure to try other values like 680R, 1K5 or 2K2.

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L.Chung

 

Of course the 1k resistor supplies some base current to the transistor and turns it on since it connects to the positive supply.
Next time I will look at the schematic before typing.

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Uncle $crooge

 

what should i expect on my transistor base so i can judge that i need smaller value resistor?

Also... is it so critical not to cross the wire even once! while i'm winding the transformer?