Total Newbie's first circuit issues...

[alottaboost]

As the title states, I'm a complete newbie when it comes to guitar effect circuit design/implementation, and I ran into my first stumbling block. I'm building this: http://www.seymourduncan.com/tonefiend/wp-content/uploads/4-v02.pdf . I've checked the circuit on the breadboard multiple times and it appears 100% correct. It does have some hum which is expected with a breadboard. My problem is that when I play open strings without touching the strings it sounds like how I believe it should, but as soon as I touch the strings, the signal gets extremely weak (ground issue?). To use this as my first learning experience, where do you think I should start troubleshooting?

Thanks in advance,
Ryan

[vendettav]

Hey man.
hmm that sounds weird to me (guess you could tellt he same eh? ) but still I dont think I can help with anything. I'll just bump your post up

[alparent]

Any pictures of your breadboard setup? Jacks and all......just might help us help you?
Make sure none of the components legs are touching. (This append to me with my first breadboard experience  )

[iccaros]

with your pictures can you post voltages around your transistor (on each pin)
Thanks

[LucifersTrip]

welcome...and plus +1 to the above 2 posts. here's the debug thread that you will be invariably directed to if you don't post enough info.
http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

though, sometimes you can get away with a nice clear closeup of the circuit and some voltage readings (if you're not sure how to take them, just ask...If you don't have a DMM yet, it is necessary if you intend to continue for a while in this addictive hobby)

for reference:

[smallbearelec]

where do you think I should start troubleshooting?

The article is a pretty good presentation of this kind of build. At a guess, there is something not right with the way the jacks, and or battery are wired. Bear in mind that the author has likely vetted his drawings and pics many times before posting, so there may be just One thing wrong, and that's all it takes for nothing to work.

Make sure that you know clearly which contacts of your jacks are tip (hot) and sleeve (ground) and ring on the stereo jack, and that they are connected correctly. They may be oriented differently on different brands of jacks.

Here are links to my articles on the basic use of a breadboard. The pics may be helpful:

http://www.smallbearelec.com/HowTos/Breadboarding/BreadboardIntro.htm
http://www.smallbearelec.com/HowTos/BreadboardSiFF/BreadboardSiFF.htm

Regards
SD

[alottaboost]

Here's what my multimeter told me about this circuit:

Battery = 9.08V
Transistor E = .04V
Transistor C = 2.34V
Transistor B = .66V
2.2M Resistor = 2.34V in .66V out
68K Resistor = 9.08V in 2.34V out
470 Resistor = .04V in 0V out (ground)
Input cap = .011V on guitar side .66V circuit side
Output cap = .001V on amp side 2.33V circuit side

[alottaboost]

And here's the pictures...

[LucifersTrip]

on quick inspection, it looks correct (assuming you used a 3904 or something with the same pinout and didn't make any part subs).

I would sub a 100K pot for the 68K R and adjust so see if you can get a better sound. I haven't built that one so don't know exactly what the voltage on C should be

[newfish]

on quick inspection, it looks correct (assuming you used a 3904 or something with the same pinout and didn't make any part subs).

I would sub a 100K pot for the 68K R and adjust so see if you can get a better sound. I haven't built that one so don't know exactly what the voltage on C should be

All looks OK for me, too.

Check that your component's leads are firmly pushed in. 

If your pin-out is correct - and it looks to be at first glance - I'd second the 100K pot for 68K resistor substitution. 
Of the two schematics posted, the electra has only 4.7K Ohms on the collector, and the SD Project has a whacking 68K Ohms.  Obviously, the two circuits are doing 'similar but different jobs' - and have their own 'current' needs, but see what effect changing this value has.

Good luck!

Hope you get sorted.

[newfish]

Hi - just thrown one of these together on my board.

Voltages are as follows...

Battery = 9.6v

2N3904 pins...

Collector = 2.99v
Base = 0.67v
Emitter = 0.06v

The only changes I made to my 'build' were to use a 390 Ohm and 82 Ohm resistor in series (roughly 470 Ohms total) at the Emitter,
and to use 3 x 10M (10 Mega (million) Ohm) resistors in parallel for the Base / Collector feedback loop.
I had nothing between 470K and 10M, so improvised - this arrangement gives me roughly 3.3M Ohms.

I get *plenty* of boost from this circuit.

Your voltages look correct - so you're almost there.

The sockets on my board are wired-in, so any 'jiggling' of cables as I pick my guitar up to test is removed (as much as can be on a breadboard, anyway).

Were this my project, I'd double check for loose connections anywhere, since the project passes signal *some* of the time...

Hang in there!

[alottaboost]

May have it fixed. I was still having the issue of touching the string and the signal dying until I picked my feet off the concrete floor of my basement... Could be common sense, but didn't think that would've been the issue. Oh well. Off to try the Trotsky!

[Joe Hart]

I could very well be wrong, but does it look like the jack with the twisted leads (red and black) has the capacitor connected to the jack's "ring" rather than the "tip"?
-Joe Hart

[LucifersTrip]

I could very well be wrong, but does it look like the jack with the twisted leads (red and black) has the capacitor connected to the jack's "ring" rather than the "tip"?

funny, to me it actually looked like one of those jacks with only 2 lugs

[deadastronaut]

all looks ok to me too....

@#$%ed guitar lead?......

[wesman26]

... does it look like the jack with the twisted leads (red and black) has the capacitor connected to the jack's "ring" rather than the "tip"?
-Joe Hart

I agree, the red wire (twisted around the black one) is definitely your output and as such should be connected to the "tip" of your output jack while the aforementioned black wire should be connected to the "ring".  Though the angle isn't all that great (for either jack really) it looks to me like Joe is right. However, I can't be sure that this would lead to the strange manner in which your circuit is behaving...

Keep us updated,
--Wes

[deadastronaut]

hmmm  i just zoomed in on both jacks...

actually they both look like they need to have the wires reversed...the black looks like its on the tip on both...


swap both jack leads on your breadboard to try it....

[Joe Hart]

hmmm  i just zoomed in on both jacks...

actually they both look like they need to have the wires reversed...the black looks like its on the tip on both...


swap both jack leads on your breadboard to try it....

I couldn't tell on the other one, but it did kind of look suspect.
-Joe

[deadastronaut]

^ yeah i'm pretty sure it is......good catch joe!....

i think he's gone now though ..

[alottaboost]

Boy do I ever feel like an idiot. That fixed it. Thanks all!