ANOTHER debuging cry for help... OCD Overdrive!

[jfrabat]

I am trying to revive those old builds that I never got around to getting to work.  This one is also about a year old, and has been sitting around waiting for me (AND YOU!) to find out the problem!

This one is a board from Tayda Electronics for the OCD overdrive.  Build instructions are here, but no schematic is given.

Despite looking like a rat's nest, the jacks and stompswitch work, as in bypass I get good sound.  But with the circuit activated, sound disappears.





Changes from original:
- Did not have 220pF caps, so used 100pF and 120pF in parallel (C3 and C6)
- Resistors were supposed to be 1% (CuteQueen from Amazon; BEWARE!), but are more like 10% in reality (measured).

Measurements:

Battery: 9.56V

2N7000 (1 -  the one at the top in the pic)
S: 0.544V
G: 0.544V
D: 1.165V going down to 1.152V

2N7000 (2)
S: 0.742V
G: 0.742V
D: 0.531V

IC1:
1: 0.650V
2. 0.644V
3. 0.518V
4. 0V
5. 0.642V
6: 1.047V
7: 1.061V
8: 1.080V

Any ideas?

[Slowpoke101]

C9 is in backwards.
R12 is 100K. It is supposed to be 100R (100 Ohms ).
Check that R13 and R14 are actually 10K.

[jfrabat]

C9 is in backwards.
R12 is 100K. It is supposed to be 100R (100 Ohms ).
Check that R13 and R14 are actually 10K.

Thanks a million!  I cannot fathom how quickly you guys catch these errors...  I imagine my dyslexia does not help, but still!

OK, replaced R12, checked R13 and R14 (they were OK).  Changed C9 (it was easier to change because the legs were too short) and put it in the right polarity.  I imagine I must have a short or something, because I still get no sound..

[Slowpoke101]

Progress!       Excellent...

Now, measure the voltages again please. By replacing R12 with the correct 100R resistor the voltages should now make more sense...hopefully..

[jfrabat]

Never mind...  APPARENTLY, when you connect the input to the amp and the output to the guitar, you get no sound when you activate the pedal...   

Thanks a million!  I now have a working OCD pedal!

[Slowpoke101]

Never mind...  APPARENTLY, when you connect the input to the amp and the output to the guitar, you get no sound when you activate the pedal...   

Thanks a million!  I now have a working OCD pedal!

Ahh..The second or third most common fault  . Rest assured that you are not alone. I generally call these types of faults an ID-10T error (which means that i am a bit of an idiot at times..well, most of the time ).

Another effects pedal to play with. Enjoy 

[Quackzed]

Slowpoke101  . i'll say!!!  took you a whole half hour from the time of the op to scan diagnose and fix it. (with a little help from jfrabat ) NICE!!! 

[antonis]

Ahh..The second or third most common fault 

Name the first one in this very moment..!!! 

[Marcos - Munky]

Ahh..The second or third most common fault 

Name the first one in this very moment..!!! 

I'd say is one among test the circuit without power, or without putting the ic, or without plugging in the guitar cable, or without turning the amp on. I did all of those ones

[jfrabat]

Ahh..The second or third most common fault 

Name the first one in this very moment..!!! 

No power to the board?

[11-90-an]

Ahh..The second or third most common fault 

Name the first one in this very moment..!!! 
[/quote]
putting polarized caps backward?

[jfrabat]

putting polarized caps backward?

I checked that box on this build...   

[Quackzed]

...Thinking it was gonna work w/o troubleshooting... 

[jfrabat]

...Thinking it was gonna work w/o troubleshooting... 

Hey, it HAS happened...  ONCE, but it HAS happened!!!