Just finished first pedal (tweako)... Got a few questions

[maurice]

Hi, just completed the Tweak O from small bear. It works fine but i have a few questions:
1) it's not cased yet and when i touch the pot it picks up fm radio signal.
2) the tone pot doesnt do much
3) the pedal doesnt really sound like examples ive heard (youtube & forums etc). Its curntly a strong boost with some minor noise, sadly without the fuzz i was expecting.

Any tips, advice or suggestions for the above?  I only substituted the 250k pot for a 220k one.

Thanks in advance, this forum has already been amazing!

[smallbearelec]

Folow the troubleshooting tips in the build article: Start with a clean layout drawing and verify with a meter that every connection is solid and actually goes where it is supposed to. At a guess, since there is little distortion, something is not right in the loop that includes the clipping diodes. Also, are the diodes oriented back-to-back? It sounds like you are very close. The radio stations will likely go away once the circuit is in a metal housing.

Regards
SD

[maurice]

Thanks for the help.

I've been around the board with a multimeter and can't seem to find any continuity errors.  Not entirely sure how to test the transistor/voltage (appologies for my fresh electronics skills).

I've attached images, perhaps those with a more experienced eye may see something obvious.

http://imageshack.us/photo/my-images/705/imag0023ra.jpg/
http://imageshack.us/photo/my-images/545/imag0024xr.jpg/
http://imageshack.us/photo/my-images/7/imag0025yc.jpg/ (less blurry)

I know my soldering is aweful, but V2 will be much prettier ...Speaking of which, where in the circuit would I place an LED to show on/off?

[LucifersTrip]

Thanks for the help.

I've been around the board with a multimeter and can't seem to find any continuity errors.  Not entirely sure how to test the transistor/voltage

Meter set on DC voltage scale >9v, probably 10v or 20v scale. Black lead to ground, red lead to the point you are measuring.

"You can also use the low-voltage scale of your meter to sniff out problems. With  your guitar plugged into J1 (necessary so that the battery circuit is complete), hang the negative lead on point O-7. With both controls at mid-range, you should see roughly the following voltages on Q1: Collector 2.8 volts, Base 1.5 volts, Emitter .95 volts. If any of your readings are off these by more than 10%, you probably have a wiring error."

[maurice]

Ok, here's my readings with the meter set on 20V:

Collector: 0.85
Base: 0.69
Emitter: 0.04

I'm guessing that means there's a problem?

[Mike Burgundy]

Battery voltage (both in circuit and out of circuit)?

[maurice]

Battery voltage (both in circuit and out of circuit)?

It's a 9v battery

[maurice]

Any further suggestions?

I've also just prototyped a 'One knob Fuzz' (http://fuzzcentral.ssguitar.com/schematics/oneknobfuzz.gif) on the breadboard.  Again, the guitar signal passes through but there's no fuzz whatsoever... totally clean on that one.

I'm totally new to all this.  Could I be using the wronf types of capacitors or transistors?

[nexekho]

What layout are you using on the breadboard?  If you're new to electronics, you could easily have misunderstood the underlying structure of the breadboard and be shorting lots of bits out.

[maurice]

It's fun learning, but yes schematic confuse the bejeebus outta me.  Chances are, my breadboard is entirely wrong... http://imageshack.us/photo/my-images/831/imag0027j.jpg/

Any feedback issue greatly appreciated

[LucifersTrip]

It's fun learning, but yes schematic confuse the bejeebus outta me.  

stick with the schematics. it will help you the most in the long run. pcbs, veros, etc are just paint-by-numbers. With a schematic, you can see the full picture easier and the pattern of the circuit and stages. In the beginning, the only thing I found difficult about schematics was the notation for the input & output jacks. It is a bit confusing. On those vintage-type fuzzes, everything else is straight forward. Each line is just a straight connection from one point to another...nothing to interpret.

Chances are, my breadboard is entirely wrong... http://imageshack.us/photo/my-images/831/imag0027j.jpg/

that breadboarding is very difficult to follow. i would consider doing it again, more straight across on one level without the wires blocking your view as much. I'll see if I have time to breadboard to show you what i mean

I'm totally new to all this.  Could I be using the wrong types of capacitors or transistors?

wrong type of caps unlikely...you can use any types that can handle at least 9v. The values are important, so yes, double-check your values.
If you did use a wrong value, you'd probably just wind up with more or less treble or bass.

wrong transistors (pnp instead of npn) could possibly give you no fuzz, but most likely would give you silence.  different gains will give you different varieties/strengths of distortion/fuzz

...and back to the original troubleshooting post. did you breadboard it first to make sure it worked before soldering?  it will be very difficult for someone to spot a small solder bridge or bad joint. You may have to try an audio probe and make your way thru the circuit one bit at a time to find your error.
http://www.diyguitarist.com/PDF_Files/DIY-AudioTester.pdf
http://www.diystompboxes.com/pedals/debug.html

[LucifersTrip]

I just breadboarded it...good smooth fuzz.

I used BC108B's,  2 x 75K's in series for the 150K, a 2K for the 2.2K (which ironically measured exactly 2.2K) and an 86 ohm for the 82 ohm

Note that i jumpered and inch or so from the first transistor so it's more spaced out and easier to work with. Both transistors are oriented EBC from left to right.

Also note the similarities between the schematic & breadboard. The transistors are the only thing you can't do the same on a breadboard since the connections are up and down...but if I perfboard this, it will be in almost the exact same pattern as the schematic.

[maurice]

You're a legend!  I'm gonna have another stab and we'll see how it goes. Your setup clears a few things up though!

Thanks!

[maurice]

I've just breadboarded the one knob fuzz again based on your advice.

Unfortunately its the same result. Clean signal from guitar but no fuzz.

To me it follows the schematic but I guess I must be missing something obvious that presumably causes the fuzz.  Again if anyone cam spot my error, I appreciate the support.

http://imageshack.us/photo/my-pages/692/imag0029zv.jpg/

[maurice]

Update:
I think I just realised the transistors were the wrong way round on my one knob fuzz breadboard (I rotated them and the signal amplified).

getting closer, but still no fuzz though

[LucifersTrip]

How sure are you that the transistors are now actually in the correct way?

Unfortunately, your breadboard pic is not close enough or clear enough & is still partially obstructed by wires, so still too difficult to really check out.

also, remember the voltages are a great diagnostic tool.  I got Q1/2 EBC ~ 0,.6,1.2 / .7, 1.2, 7 with a strong battery over 9v

[LucifersTrip]

you enlarged the pic? anyway, here's the important part rotated...maybe someone will see an error, but still very difficult to check the way you breaded it:

[Mike Burgundy]

I asked about the battery voltages in- and out of circuit, because your measurement looked off (plus there's just one tranny measured) and we want to know what causes that..
Debugging is a process of elimination - no use figuring out weird voltages unless you're sure the battery delivers. Difference between no-load (out of circuit) and in circuit also might reveal something.
That said, refer to the debugging sticky, and keep at it. You'll figure it out, and learn a great deal in the process.