sunking help, With Voltages! (for real this time)

[jtn191]

I made this thread http://www.madbeanpedals.com/forum/index.php?topic=1672.0 only to find there were some problems with my build.




LED: works
Bypass: works but noisy
Effected: oscillates similar to playing around with my Fuzz Factory/Zombii build's "stab" pot; no guitar signal

Jacob, I haven't gotten around to making a testing rig yet, but that is sitting on my list of things n' pedals to do this summer  

I really appreciate any help

[jkokura]

The first thing I'd recommend is taking it out of the enclosure. If you have done it true bypass than remove the switching, but if it's buffered leave the switching in. Remember to make sure that both jacks are grounded to the circuit as well.

If it works right there, then you know the problem isn't with the board. If it still isn't working it will be easier to repair.

Jacob

[bangerang101]

 These are kind of general troubleshooting tips but I figured I would mention them anyway...

Did you try it out with the back off of the enclosure? It looks like with the way you have it wired up, the back may be shorting against something on the board (I usually put 3m foam tape on the back of the boards to protect them from shorting). I know it's obvious but I figured I would throw it out there...

Also, make sure you have no solder bridges on the board (components soldered together that aren't supposed to be connected).

Triple check your wiring too!! 

[jtn191]

yes sir, I took of the back (and I had electrical tape there to prevent shorting). I suspect the input/output and switch may be shady b/c I've never soldered resistors to the switch like that before. Does anybody know what might cause oscillating in an overdrive...specifically this sunking?

[jkokura]

It could be any number of things, however, most often it seems that it's either a power wire issue or a bad IC. Have you taken it out of the enclosure to work on it yet? Is the oscillation still there?

If so, I'll have to recommend you start going through all your parts and begin to double then triple check all the values and orientations. Even if you're a veteran pedal builder this is the first place you need to go about checking it. This is the first thing I do when something doesn't work.

If you haven't taken it out of the enclosure yet, I recommend you do so, then do the step above. Once that's done, triple check your offboard wiring. Don't assume you've got it right, check it a third time.

Once both of those things are done, I have some more ideas I can share with you. Here's what I need you to do:

1. Verify it's out of the enclosure, and let us know what kind of bypass you're using (I think from the pictures you've got a DPDT so probably it's buffered)
2. Verify all your parts are correct, and you've checked this multiple times, both for value and orientation.
3. Verify that your wiring and offboard parts are correct, and you've checked this multiple times.
4. Tell me EXACTLY what is written on the top of the 3 IC's.

If after that you're still not sure what to do, please let us know whether or not you have a multi meter and I'll get you to take some measurements.

Stick with this, we'll get you working. Trust me it's worth it.

Jacob

[jtn191]

I'll have to wait until the weekend before going back into the "workshop"

[jtn191]

doh! one problem I found so far was I forgot to ground the input jack...

[jkokura]

That wouldn't necessarily be a problem. In the enclosure, the jack would have been grounded. Outside of the enclosure, you'd need to ground it.

Jacob

[jtn191]

Ok, I'm a noob at measuring voltages on ICs (my DMM only has a 2V DCV setting, and they sometimes are fluctuating...but the pedal is oscillating) but here goes:

    IC 1  (pin->voltage)    TL072 CN
1  0
2  -3
3  0 to -4
4  7
5  9
6  0 to -3
7  0 to -3
8  -3

   IC2        TL072 CN
1   0 to 4
2   0 to 4
3   1 to 4
4   1 to 4
5   12
6   1 to 3
7   1 to 4
8   1 to 4

   IC3   MAX1044
1   5
2   0
3   8
4   12
5   2
6   0 to 2
7   0
8   18

[jtn191]

bump  

here's what it sounds like: http://www.filefreak.com/files/797910_dbv8n/sunking.mp3
btw the humming there is not from the mic/computer...it's from the pedal's bypass


I'm starting to wonder if my whole switch wiring/configuration is off...

[gtr2]

Hmm...

Your voltages are all so far off that I'm not sure that your measuring correctly or listing the voltages for the proper pins.

For example pin 8 of IC3 should be close to 9v the same as your power source.

Find the data sheets and follow the pin outs for the pin numbers.  When measuring place the red probe on the pin and the black probe on ground.  Be careful not to touch two pins with the red probe when measuring or this will change your reading.

As far as your DMM, it sounds like you have one where you need to set the range for measurement.  You need to pick the range.  Pick the setting higher than 2VDC it may be 20VDC.  If your using the 2VDC it wont read properly and some DMM's will just display a 1 that fluctuates around.  I don't know if this is the case with yours.  You need to get familiar with your model.

Josh

[jtn191]

when I do the above, I'm only getting 0.02 from the 9v DC jack...

I'm putting the black probe on ground, red on power lug   . It's a radioshack dmm but measures resistance fine

[gtr2]

Ok just to clarify...

You have you multimeter in the 20v setting and are placing the red probe on the 9v+ and the black on ground and your only getting .02?  Is this on the board or DC jack?

[jtn191]

bleh noob mistakes before. here's the real measurements:

IC 1  (pin->voltage)    TL072 CN
1  4.44
2  4.44
3  3.4
4  0
5  4.4
6  4.4
7  4.6
8  8.8

   IC2        TL072 CN
1   4.4
2   4.4
3   4.4
4   -8.6
5   4.4
6   4.4
7   4.4
8   16.05

   IC3   MAX1044
1   8.8
2   4.39
3   0
4   -4.3
5   -8.6
6   4.2
7   6.5
8   8.87

The pins on IC3 are the farthest from specified on build docs, but not that far off...

If it isn't the ICs, then it's wiring on the switch/pots/other parts?

[gtr2]

Your voltages look good.  It may be time to build an audio probe and work your way through the schematic.  The bypass should not be "hummin" like that so something is definitely up 

Taking some nice pictures with everything out of the enclosure may help us track down if something is incorrect with the wiring as well.  Usually something like this is an easier problem (if there is such a thing).

Josh