Help Debugging Fuzz Factory Clone

[platypy]

Ok, I lifted the legs of the caps and it seems that Q1 is now getting some voltage. The collector is getting 1.37v, the base is getting 0.63v, and the emitter is getting 0v.
Correct me if I'm wrong, but this makes me think that one of those two caps is shorting to ground.

What happens now?

[duck_arse]

well, I'd put my ohm-meter black-to-ground, and then red to each of those free cap legs. if one show 0R, I'd guess it the problem. maybe. antonis, where are you?

[platypy]

Ok, I tested the legs of the capacitors. Neither gave me any reading. Just to clarify, I lifted the legs of the capacitors that were furthest away from the transistor. Does it matter which legs I lifted/tested?

Also, the leg of the 100nf cap that I hadn't desoldered (the one connected to the 10k resistor and the 220k resistor that's attached to the base of Q1) reads at 7.95k ohms. Is this just normal, or could it mean that something is wrong?

Thanks!

[antonis]

I've missed you guys... 

What exactly are we measuring now and for what purpose..??


<the leg of the 100nf cap that I hadn't desoldered (the one connected to the 10k resistor and the 220k resistor that's attached to the base of Q1) reads at 7.95k ohms. Is this just normal, or could it mean that something is wrong?>

Something is very wrong..!!

If you measured between 10k/220k/100nF junction point and GND you shouldn't get any resistance measurement..
(provided of Q1 cut-off state, of course..)

[platypy]

Right now we're measuring the parts of the circuit that deliver voltage to Q1, since it seems to not be getting any. The 10k/220k/100nf junction seems to be at 0v when it should be close to 9v.

I'm completely lost right now, so I'm gonna need you guys to tell me what to do. I can't seem to find any way that the junction in question is getting grounded, nor can I think of any hypothetical scenarios where that would occur either. 

Any ideas?

[antonis]

Check, step by step, for continuity from +9V to upper Stab pot -> lower Stab pot -> upper leg of 10k resistor -> lower leg of 10k resistor  e.t.c.

(continuity means 0R for wires and respective values for resistanses..)

[duck_arse]

don't sweat exact marked resistances when tracing per antonis instructions, they will be lower in some instances, but they need to show 'connection'.

[antonis - 1V37 Vcc on Q1 is still way too low, isn't, no matter the pot setting?]

[antonis]

[antonis - 1V37 Vcc on Q1 is still way too low, isn't, no matter the pot setting?]

Not low enough for an - almost - saturated BJT.. 

Something sneaky is happening around Collector/FB bias resistor..
(an oversized R_C or an undersized R_B perhaps..??)

My suggestion is to delete/bypass/jump Stab pot and connect 10k directly to +9V.. 

[platypy]

It's working! Do you know what it was? The Gate potentiometer's #1 lug was soldered one row down (at the 10k/220k/100nf junction) and was shorting to ground.  I resoldered it and now everything works great!

Thanks so so much for the help you guys! I really appreciate it.

Now if you'll excuse me, I have another broken pedal waiting in the wings for me to fix it, and hopefully I can do it all by myself this time.

[antonis]

It's working!

@Duckie, let's go to another thread to continue our backgammon match.. 

[duck_arse]

come back, platypy - we need you to measure and post your voltages, now you have it working. and to your fault - this is why we want photos where we can see the components and their placements. well done on debug #1.


antonis, is that the one with the triangles? do we have to play for money? [I wouldn't want to drag you away from a mosfet boost discussion.]