Starting Really Simple - One NPN Bazz Fuss - Sporadic Sound

[billynewmusic]

Hey everyone,

I'm breadboarding my first circuit to find out how i like the sound and make any tweaks before soldering it all up and what not.  I wanted to start with few components - and just know i could make a sound through the circuit before experimenting with different components.  I'm using the 7 minute fuzz schematic.  It works(ish), but its very sporadic in when it puts sound out, and when it does - its loud. REALLY loud.  I read the debugging page about blatty and gated sound - and think this may be the issue, but it doesn't really say how to fix it. 

I also don't have the voulume pot hooked up - but that shouldn't be the issue... should it?

Do i just need to use a new transistor?

Here's the schematic - http://www.diyguitarpedals.com.au/shop/boms/7_Min_Fuzz_Schematic.pdf

Thanks in advance!!!!
Billy

[anotherjim]

What type of capacitor have you used for C1? If electrolytic, the + end should go toward the transistor. The wrong way round, it will draw enough leakage current to upset the transistor bias.
Have you used the correct transistor? It's drawn as a normal NPN BJT but the type required is an NPN Darlington.

[billynewmusic]

What type of capacitor have you used for C1? If electrolytic, the + end should go toward the transistor. The wrong way round, it will draw enough leakage current to upset the transistor bias.
Have you used the correct transistor? It's drawn as a normal NPN BJT but the type required is an NPN Darlington.

Thanks for posting Jim!  C1 is electrolytic, and i DO have the positive leg going to the transistor.  The transistor is a Darlington.  Do you think i should swap it out for a difrrent one just to check?  I have a few spare NPNs from Radio Shack lying around.

All in all - i feel like the tansistor must be the issue though.

[anotherjim]

The original circuit is a normal tranny with a 1N4148 diode (that BAT one is a Schottky).
If you search you'll find the original circuit for this effect -  breadboard that and tweak from there.
Don't expect Big Muff smoothness from something this simple though

[GibsonGM]

Shouldn't blatt too bad, tho. I'd use the standard NPN and try to get a 'normal' diode.

[PRR]

> i feel like the tansistor must be the issue

Why? You can't "feel" electricity. (Not at the 9V level unless exceptionally sweaty.)

My 2 cents is on a poor connection somewhere. Works sometimes, not other times.

However if you are sure it isn't that, the next step is to "look" with a Volt Meter. The joint between Q1 and R1 (Q1 Collector) should be near 1.5V. Anything much different is wrong. Find the error.

[LucifersTrip]

you didn't accidentally use a 100uF for C2?  I would also hook up the vol pot and turn the volume down to see i you have the same tone. There are many circuits where the bass increases with volume...

..and of course, did you measure the transistor collector voltage to see if you're close to working ones?

[anotherjim]

Is it me, or is C2 in that circuit (and some other versions I've looked at) the wrong way round? Shouldn't it me Negative of the cap to the output/vol pot? If that is an electro, and the pot isn't used, it's leakage could be upsetting whatever it's plugged into (and we don't know what that is).

[LucifersTrip]

for .1uF it won't (usually) even be electro