HELP A GUY OUT!!!!

[sabsmaniac]

i tried to build the mxr distortion but i got a weird fuzzy sound instead of distortion. i was wonderin if anyone had a pcb for this pedal or anyine could give me some advice?! thanks...

[robbiemcm]

Sounds kinda like what happened to me. Nobody can figure out what's wrong with it. Not that anyone has really tried... well 2 people have.

[geertjacobs]

Well,

Most of the debugging advice anyone can give you is written down in the sticky topic on top. "What to do when it doesn't work".
This is really a great help in debugging and it bundles the best advice that anyone can give you without seeing your pcb.
Most of the diyers have made most of the mistakes that are mentioned in the topic.
:wink:

Good luck!

[aron]

If it's fizzy it's probably a misbiased opamp or the output or input caps are incorrect. Hard to tell without seeing/hearing it.

[robbiemcm]

What is bias? Is that like... the C,B,E of a transistor and stuff? Like getting the right metal bit in the right place?

[petemoore]

What is bias? Is that like... the C,B,E of a transistor and stuff? Like getting the right metal bit in the right place?

I need to read more...
 Bias/misbias is the voltages that occur at the opamp pins. On Re'gular opamps [386 has some exceptions] resistors provide 1/2V [V divider, two same size resistors between V+ and V- rails of PS].
 Also other resistors setup bias on the opamp pins.
 Reading the voltage of each pin, from ground, can tell you whether the opamp is setup with V's that allow operating conditions.
 Clip Black DMM lead to a known ground [like something connected to pin 4 of standard oa] set DMM for measuring Volts in say ...2v-20V range,
touch red lead to pin 1, read and write down that reading, same for pin 2, then 3,4,5,6,7 and 8...before you do that, so you remember...always measure the battery Voltage, in and out of the circuit.
 just a suggest...measure to confirm there is not continuity between V+ and V- on the board...if you have continuity you must find the short or you'll burn up battery...not that you would, I did, 'saves battery test' I calls it.
 I 'beep' check all ground points in a circuit while I'm checking voltages, leaving black to Gnd. point, and resetting the meter to continuity checking, touching red DMM Probe to all gnd. points and listen for beeps.

[j0shua]

Fuzzy hmmmm

MXR Distortion + is real little fuzzy but try to check the 10Pf cap from pin 2 ( Inverter Imput ) and check for the Diodes correct side....

Remember if you use other diodes the sound change !  

cheers!

[ryanscissorhands]

http://www.diystompboxes.com/sboxforum/viewtopic.php?t=27209&highlight=biasing+beginners

The above thread was started by myself, because I had similar questions about biasing. aron cleared it up quite well.

[sabsmaniac]

thanx for all the advice--you know i tried changing the diodes and the sound was the same??!! i tried making it on a bread board today and i got o different but still fuzzy sound-- maybe the schematic is screwed man im out of ideas except for what you guys said... thanxs if anyone has any ideas just post it...

[NaBo]

Post ALL the information mentioned in the "what to do when it doesn't work" sticky.  It's a little tedious, but you'll get your answer in no time. The people here will be able to almost pinpoint where the problem is occuring in a circuit like the dist+.  In the meantime, double and triple check the orientation of parts, check for solder bridges, check wiring, check your layout against schematic.

Personally, I've etched a PCB backwards, completely reworked the layout and bent back the IC pins for it to work... then it didn't.  After all that work, I was so PISSED that it didn't work the first time.  Then I realized I had soldered both legs of an electro to ground (and all the stuff connected to the + lead's trace too)...   :x