dumb question re; audio probe

[dansamp]

I know this is pretty lame but I am at my wits end !!

so far I am on a pretty big losing streak with building effects
it seems as if everything I build has a problem
before I give up could someone please explain how I use an audio probe to debug my circuits

I have a feeling all of my mistakes are ground related and I keep repeating the same mistakes
two tonebenders (only works if I am touching Q3 and the chassis  other one if I touch the back of the vero board
a foxy brown clone that I can't find the right transistors for
and lastly a colorsound overdriver that has no sound when engaged although all the voltages are good


is there anyone in the los angeles area that could give me a one on one tutorial on effects

I am willing to pay

it has gotten to the point that I am obsessing and wasting a lot of time building effects that don't work and not enough time playing music

Thanks in advance



Dan.........................

[Roobin]

Well, an audio probe works by basically touching the circuit at a particular point, and you can hear what the signal is like at that stage. This allows you to identify the point at which the pedal isnt working.

Don't give up; many things do not work first time, or at all. But don't give up playing either!

If you want a tutorial, you could:
i)search here or elsewhere
ii) post your problems online; theres always plenty of help

[tcobretti]

Dude, if it's any consolation, I've built 20ish pedals, and they rarely work right from the start.  Lately I've been using stripboard instead of perf, and things have actuall gotten far worse.  It seems I am unable to solder strip board without solder crossing the gaps.  The latest one is a Si FF, one of the simplest pedals known to man, and I haven't gotten it to work yet.

The audio probe and a multimeter are the key tools that I know of to find problems.  Use the probe to find where the signal stops, then use the multimeter and your schematic to figure out what you did wrong.  Work at it steadily and don't give up.  Compare multiple schematics if you can find them.  If you get totally frustrated, I'd recommend building something from a purchased PCB, that way it's more likely to work and maybe you'll remember why this stuff is fun.

good luck
travis

[psiico]

You know how to make an audio probe, right?  I made mine from an old guitar chord.  I cut off one end and soldered a cap to the hot lead and an alligator clip to the ground lead.  To use it I plug the chord into my amp and my guitar into the effect.  Clip the alligator clip to ground somewhere in your circuit (I usually use the ground lug of the input jack) and touch the probe end to various points in your circuit.  Start at the beginning right where signal goes into you pedal, keep moving the probe to the next component as each one checks out.  When the signal stops, there's your problem.  IE. if you have signal after a cap but then after the next resistor there's none then the resistor is the problem.  I've only had to use it once so far and I found the problem in seconds, might have taken hours without the probe.

[aron]

Imagine the first time I wired up that audio probe. Amazing! I fixed a bunch of circuits with that thing!

[dansamp]

OK,
here's the latest
last night I sat down with my layout, audio probe and one tall Guiness 
I found one resistor in the wrong location, one cap in the wrong location and one trace not cut out !
after sorting that out I had a working pedal but.............
the treble pot didn't do anything, took an ohm meter to it measured across the sweep and no change
swapped out the treble pot now that works
not sure if the gain knob is working right it's pretty much on or off no range at all
tried another pot and same thing ( Is this correct ??)
it seems the only knob that seems to be working correctly is the bass pot turn it up and the sound gets very full with lots of gain
the treble pot works and increases treble put it doesn't have the same impact as the bass control
so far I haven't installed a volume pot but I don't think that would change the operation of the gain control
using the audio probe (how does one know how much of the signal should get through?? )
obviously I get signal coming through the entire circuit but if the signal is weaker does that mean there is a problem at that location??

I am running a signal generator through the audio probe


thanks for your time

Dan................

[slacker]

If you're talking about the colorsound overdriver then the gain pot sounds about right. You should get a boost in volume over most of its range but the distortion only comes in right near the end of the travel. The pedal was originally designed as booster to overdrive valve amps, so the fact that its own distortion wasn't very controllable probably wasn't much of an issue. If you do a search of the forum there's a few good posts about improving the range of the pot.
Not sure about the treble control, mine has quite a noticeable effect.

[dansamp]

the gain pot comes on right away from 0-2 is full output
after that turning the pot more doesn't increase the sound
does that make sense ??

[rockgardenlove]

Make sure you're using the right kind of pot, it sounds like you have a linear pot, I think the gain should be audio.

[dansamp]

yeash I am using and audio pot
thanks


another audio probe question
how can you tell which way the audio signal should be going ?
obviously there shouldn't be any sound at the ground points, correct???

but it seems the first tranny has a large audio signal at the base and collector then it is reduced at the emitter
the second tranny has sound at the base and collector but it is reduced in volume
and then the third tranny the signal is even more reduced
is this correct ??

[Peter Snowberg]

If you can post a link to the schematic you are using it will make debugging much easier. Without that we're shooting in the dark. 

Don't feel bad about things not working the first time. Most people will have a number of small problems with their first pedals. The trick is to remember that with the right tools, you can fix almost anything. Just take everything in steps.

[dansamp]

here is the circuit in question

thanks   

http://aronnelson.com/gallery/albums/slackers-stuff/newcsoboard.sized.jpg

Dan............

[slacker]

Here's the schematic