Egodriver issues

[Outtagetme]

Hi guys,
so I've built the Egodriver (the version released on 05.2012), but I'm having problems making it work. Actually I built a testing rig (as per Jkokura thread), and I use an audio probe as well.
So here's the issue: actually the pedal doesn't work at all. I get a very very very low output, and it's so low that I can't say if the pots are working or not.
With the audio probe, I can hear the sound until pin 3 on the IC: from there, no more sound at all anywhere, assuming that my output would be on pin 8 (am I right?)
I checked the power supply and it's 9V (measured on PCB).
I measured the voltage on IC's pins and here are the readings: everywhere from 8.5 to 8.8 V, except for pin 8 where I have 9V. I found out on this forum that the readings on the Egodriver IC should be around 4,5 V, except for pin 4 (0 V, it's connected to ground) and pin 8 (which should be 9 V, is that the output?).
I replaced the IC to see if I had a faulty one, but nothing happened. Same readings as above.
I checked the connections as well and they all seem good to me.
Can you help me?

Thanks,
M.

[RobA]

Output should be on pin 7. Pin 8 is the positive supply on most dual op amps.

You should hear audio on pin1 and pin 5. Pin 1 is the output of the first stage on the schematic and pin 5 is the input to the second stage. You can narrow down where to look by listening at these two pins.

[Outtagetme]

I checked and I get only a very very low sound on pin1, no sound on pin 5 and clear sound on pin 3. I checked the soldering and actually they look good.
I don't know what to do next.

M.

[midwayfair]

post voltages.

[Outtagetme]

I posted them in my first post (the IC voltages), I checked them again after re-soldering pin 1 and pin 5 and they dind't change.

[RobA]

What's your voltage at the junction of R14 and R15 (VB)?

[Outtagetme]

9V

[RobA]

9V? This should be after the voltage divider set up by R14 and R15. The same value should be on the + pad for C10. I'm thinking it should be somewhere around 4.5V (assuming your input voltage is about 9V).

[Outtagetme]

Actually I measured at the junction between R14 and R15, I get the same reading of 9 V on the + pad for C10 (on the - pad as well..). Yes, I'm using 9V as input voltage. I checked the resistor values and they're as per project. Should I try and replace them?

M.

[RobA]

The - pad of C10 should be at ground. At this point, I'm guessing there is a grounding issue in the wiring. Can you post photos of the front and back of the board?

[Outtagetme]

Yeah actually I'm not an electronic experts but I know that there was something strange with the 9v reading on the C10 - pad. I replaced the two resistors but nothing has changed (same reading). Here are some pictures.
Sorry for the low quality.






M.

[Outtagetme]

Actually if I measure on the ground plan around the pcb I get 8.6 V..a ground issue, you were right. Now what is causing that?

M.

[RobA]

Look for solder bridges visually. You can check with the continuity checker on you DMM too. I'd start by checking the continuity between the 9v input and ground and each of the pads of r12 and ground. And then just keep looking from there. Any solder, even a tiny bit, that bridges between pads or from a pad to the ground plane will cause a problem. For example, it looks in the photo like the output pin (pad 2 on the volume pot connection) could be bridged to the ground plane and pad 1 of the pot. Check around the board and any suspect spot you see, reflow the solder and clear the bridge.

[Outtagetme]

Ok thank you I will do that now.
One more (newbie) question: can I check a soldering joint as well for continuity? I mean, in general a good solder joint will be conductive..a bad one won't..so I might check for bad solder joints with that tool, right?

[RobA]

Yeah you can. You can use the continuity checker to check to see if the lead is connected to the trace by putting one probe on the lead on the top of the board and one on the trace. That can be a bit cumbersome but it is useful at times. The other thing you can do is check the continuity from part to part on top of the board (bit hard for caps). I usually start by doing this and following the power connections and signal connections through the schematic.