Need basic VCO help!

[BlueCollar]

I've started my x0xb0x project and followed the build instructions as closely a possible. Note: My kit came from adafruit.

The power supply is successfully built. I am testing proper +12, +5.333, and 3 volts on pin 7 of IC11. Each of the tests up to the point of checking for a sawtooth is successful. The problem I am experiencing is there is no sawtooth showing up on my oscilloscope. Also, when I check for a 8.5v bias at R105, I am actually getting a read of 0v, which corroborates with the scope showing nothing.

Attached is a photo of the circuit - I can supply more if needed.

I have went back and double (triple!) checked the solder joints and the parts' orientations on the PCB. I have absolutely no clue where to go from here. If I had to guess, I would wonder if one of the components is damaged.

Please help - I do not know how to perform further tests to isolate the problem. Thank you in advance!
-Bluecollar

[BlueCollar]

Note: the image preview does not show the complete height of the captured image. If you scroll down over the image, you will see the VCO section of the board. Thanks.

[antto]

just to check.. you should have powered the IO board, then J4 should be connected to the mainboard so that you have GND, 5.33 and 12V there, and you have to supply external control voltage (3V or so) to R89 iirc so that the oscillator has some pitch
if you've done that and you get no oscillator output at the waveform switch - then indeed something has went wrong, but no idea what..

[BlueCollar]

Yes, I have powered the IO board. The image above does show that I have brought the jumped 12v GND and 5.33 lines over, and the manual says to apply 3v CV to R90 (not R89 as you mentioned).

As I mentioned, I have successfully tested all the voltages up into the VCO, including pin 7 on the IC.

I am really stuck from here though, getting no voltage on the saw out. Any help would be greatly appreciated.

[BlueCollar]

Can anyone lend a hand? I am surprised I haven't gotten more responses.. I have switched out transistors but to no avail. Like I said, all the voltage measurements in the guide 100% succeed before the saw out read, which is totally dead. I have no idea how to diagnose this :|

[deejayraoul]

Edit: i can't see clearly from you pic but it looks like one leg of R101 isn't soldered?

Did you check and recheck all component values and orientations?
Also check continuity with the schematics at hand, it might be a bad solder joint. Otherwise it might be a failing component.

[deejayraoul]

If all else seems correct it might be the opamp failing. I don't know if it's possible to test in place. You could maybe desolder it and put in a dip socket so you can easily swap it out.

[deejayraoul]

Also check this post±
viewtopic.php?f=12&t=67087
I notice some of your resistors are not orientated as printed on the board, You might be measuring the wrong side of the resistor.