Help Debug A DOD Overdrive 250

[Verran]

Hey everyone!  I've been reading here a while, and finally got confident enough to do a beginner project.  I have a lot of background in digital logic circuitry from college, but I've never done much with power systems.  Hence, anything that's not 0v or 5v is foreign to me 

So anyways, I read through the Intro, Power Section, IC Hookup, and Off-Board Connections pages.  I built the power section and my full and half voltages were 9.03 and 4.47, which were fine.  Then I kept going and stopped at the testing part after the IC Hookup.  My voltages on the IC were:

1 - 0.04v
2 - 4.21v
3 - 3.07v
4 - 0.04v
5 - 0.04v
6 - 4.54v
7 - 9.03v
8 - 0.00v

These all checked out, except 2 should be 4.67 instead of 4.21, and 3 should be 4.46 instead of 3.07.  Pin 2 seemed like a fair margin of error, but Pin 3 was clearly wrong.  I couldn't figure out why since it's a very simple hookup, but I kept going to see what the result would be.  I checked the resistor value for R3 (470K) both with a DMM and by the color bars.  I figured I could swap the 470K resistor later just to see what effect it'd have on the Pin voltage and on the sound as a whole.

I finished the whole thing, and plugged it in.  I was greeted with a substantial hum that seemed to grow as the gain was turned up.  The hum was not so bad as to totally hide the sound of the pedal though, so I played it a bit.  It sounded pretty good from what I could tell, but even at zero gain there was still a pretty beefy distortion sound.  I'm not sure if that's part of the design, and it wasn't like a Metal Zone or anything, but it's definitely not clean.  At full gain, the hum makes it very hard to really get a feel for the sound, but it's definitely a meaner distortion.  The volume pot works exactly as I'd expect with any gain setting.

Also of note:  Taking a reading from pin 3 of the gain pot or touching the gain knob or the board base make the hum more pronounced.  That leads me to believe it's a grounding issue, but I've checked continuity at all the ground points and they are all connected.

Here's some other readings that may help:

C1 - 3.05v / 0.02v
C2 - 4.22v / 0.04v
C3 - 4.22v / 4.54v
C4 - 4.54v / 0.02v
C5 - 0.04v / 0.04v
C6 - 9.03v / 0.04v
C7 - 4.47v / 0.04v

D1 - 0.04v / 0.04v
D2 - 0.04v / 0.01v
D3 - 0.04v / 0.01v

All three terminals on both pots read 0.04 no matter what I do. 

The IC voltages don't change if the gain is adjusted.

Here's the schematic from the guide:


Here's some pics of my breadboard (sorry, they're high res, but I figure that's best in this case):
http://img110.imageshack.us/my.php?image=dod2503ej9.jpg
http://img110.imageshack.us/my.php?image=dod2502fc5.jpg
http://img408.imageshack.us/my.php?image=dod2501cx1.jpg

Thanks for reading, and I hope you can help me out because I'd love to make this my first of many DIY pedals.  If you need any other info to help out here, just ask and I'll get it for you.  Thanks again!

[petemoore]

1 - 0.04v  NC
2 - 4.21v  Pretty good
3 - 3.07v  Low
4 - 0.04v this is wierd, should be measured to and from ground, should be 0v
5 - 0.04v  way low, I wonder what's up with 5 and 4 being .04v
6 - 4.54v  About smak dab mid bias point
7 - 9.03v  yupp
8 - 0.00v NC
  I'd start with pin4, and get a ground connection type reading [0.0V] at that pin.
  The voltage divider is a good place to check voltage, should be about 1/2v there.
  Then if pin 5 isn't connected to pin 4 [no stray connections of any type], I'd start measuring resistors through distant connections [to test resistance and connections @same time], from and around that pin.
 

[ulysses]

are you breadboarding it? why not just build it on vero - i just built the DOD '77 grey OD 250 on vero. i can send you the layout if you like.

cheers
ulysses