sometimes, it's the simplest circuits...

[runmikeyrun]

Okay, lately i've having a problem... every time i go to build a single transistor circuit, it doesn't work.  I have no idea why.  If i'm lucky i'll get a slight bit of signal for an instant if i strum really hard.  I've tried different bias resistors and to no avail.

This is ridiculous, i've built dozens of circuits and never had this problem before.  The latest i've tried is the Bazz Fuss.  Here are my voltages, if anyone could help i would appreciate it.

V+ = 8.89
C = 8.6
B = 0.49
E = 0

Thanks
Mike

[Brian Marshall]

voltage on the base needs to be higher.

[Johan]

its been a long time since I looked at that schematic, but it uses a diod for the biasing, right?
check the direktion of the diod.....and allsays double check the pin configuration of your transistor..sometimes even transistors with the same number but from different manufacturers differ...

Johan

[petemoore]

The collector is very close to the +rail...should be about a little more than 1/2v, or 4.5-5.5v with a 9v battery. Probably a miswire or 'turned around' transistor or diode.

[R.G.]

V+ = 8.89
C = 8.6
B = 0.49
E = 0

Let's think for a moment.

The collector resistor (presumably there is one) is dropping 8.89-8.6 = 0.29V across it. If we knew the value of the collector resistor, we could calculate the amount of current going through it.

With 8.89V to play with and only 0.29V on the collector, the transistor is barely turned on, and this is confirmed by the 0.49V on the base-emitter junction. So any negative signal turns the transistor further off. Any positive signal turns the transistor on, but it has to be a biggish signal to cause much to happen, so you'll only kick the transistor in to a big signal when you hit it hard.

The base needs more current.  You don't give us much in the way of details about how the base is biased, so it's hard to say what to do. If you're using the two-resistor B+ to-ground circuit, increase the bottom resistor or decrease the bottom one. If you're using the collector feedback resistor, decrease that resistor. If you're using collector-to-base resistor plus a resistor to ground from base, decrease the base-to-ground resistor.

If the collector was sitting at, say between 4 and 6 volts, then any signal would be amplified. That's the place you might want to hit unless you're after some special effect.

[R.G.]

Forgot - for a simple look at how transistors work and how they're biased, check out "How it works" at GEO. Not nearly where I want it to be, but it explains this problem, down near the end.