I hit a snag/Any Chicago x0x'ers?

[synth505]

So I started putting together my x0xb0x and didn't get very far before I hit a snag.

In the online x0x manual it is page 3, just after number 5. When testing that the trimpot adjusts the tuning voltage it doesn't adjust at all. I took the trimpot out, thinking that I got it too hot, but when I tested the resistance with the multimeter it seemed to change as I turned it. So..I decided to not go further until this issue is resolved seeing as how the tuning frequency is KIND of important, haha.

Another odd thing is that on the online manual it says to test at pin 1 of J4, while my paper manual that came with the Willzyx kit says to measure at pin 5. I have been assembling following the paper manual.

If anyone has any ideas for how I may be able to fix this, I would love some input and would appreciate it greatly. If there is any more information needed to diagnose the issue, just ask and I will answer to the best of my ability.

On another hand, if there are any x0x'ers in Chicago that would be willing to assist me with this build I would be more then glad to bring the beers

[synth505]

So I decided to snap some pictures to see if they may make assistance easier

Edit: In these pics I took the tuning trimpot out because I thought I fried it, so I wanted to test it.

The full resolution pics-
http://img.photobucket.com/albums/v76/p ... CN1488.jpg
http://img.photobucket.com/albums/v76/p ... CN1490.jpg
http://img.photobucket.com/albums/v76/p ... CN1489.jpg

[MMM]

You need to install D44 to D47 before you can measure anything meaningful.

[synth505]

Aha! That is probably it..I placed all the other components at that point in the manual except D44-47, so no wonder it doesn't work! Now to resolder the trimpot and so forth..

If I am still getting weird readings I will post again. Thanks for pointing out my mistake!

[synth505]

So I put in the diodes and resoldered the tuning trimpot back in and I am able to get the range of voltage needed.

I have now completed the sawtooth portion of the VCO, but I don't have an adjustable power supply/3V. Is there a way to test the sawtooth without applying the 3V to R90? How important is this step of the process? Should I continue on building the rest of the oscillator or wait until I make sure the sawtooth works?

I appreciate all the help you are all giving very much!

[MMM]

If you have an oscilloscope you'll see the sawtooth wave without applying any voltage - but you won't hear it because the frequency is very low.

If you want to make sure the sawtooth works you could apply a voltage in the general 1v to 4v range to R90. The build manual suggests using two AA batteries as an alternative.

[synth505]

So I found a toy that i'd broken while circuit bending and noticed it had a 2 AA compartment, so I used that to hold the batteries and just alligator clipped them on.

Attached is my x0x's first sawtooth! I imagine it looks weird because I was using the Max/MSP scope~ through my Mbox. I listened to it through my speakers and it sounded like a sawtooth!

The only thing that was different during my testing is that I connected the 3V to the opposite side of R90 then shown in the picture because of the way I soldered that resistor in. Is this fine?

Edit: Finished the square wave and both work! Here is a short video of the scope~ reading (man it looks screwy, haha)

http://www.youtube.com/watch?v=3Tf0_qi0I7o

Edit 2: [SOLVED] Another question - the 74AC174 chip that goes in IC9, in my kit I see an HD74HC174P chip, is this the same one?

Edit 3: Almost done with the VCF! May have questions about testing it, will update if so.

[synth505]

Ok, so here is where I am at now.

I have completed putting all the parts for the VCF in (pictures attached) but am not understanding how to test the filter. I probed around on the cutoff and reso knobs, but didn't get anything. I thought this may be because of how I attached the alligator clips to a 1/4 cable, it is quite wonky.

Any advice on where to go from here? Putting this thing together is stressing me out hardcore -_- I am going to flip if this thing doesn't work.

[MMM]

You should of course attach again the 3V to R90 so you're getting a signal within hearing range.

Probe point is the pin of VR4 that is closer to C13. The signal is going to be VERY weak compared to the oscillator signal, though.

[synth505]

You should of course attach again the 3V to R90 so you're getting a signal within hearing range.

Probe point is the pin of VR4 that is closer to C13. The signal is going to be VERY weak compared to the oscillator signal, though.

So it looks like I am getting a signal from that pin and it was considerably weaker/didn't sound like the pure saw/square of before.

I am assuming I can move on to the envelope?

[MMM]

So it looks like I am getting a signal from that pin and it was considerably weaker/didn't sound like the pure saw/square of before.

Does the signal change when you turn the cutoff or resonance potentiometer?

I am assuming I can move on to the envelope?

I probably would move on, yes. Even if there are problems they might be easier to fix when you have a mostly working xoxbox.

[synth505]

So it looks like I am getting a signal from that pin and it was considerably weaker/didn't sound like the pure saw/square of before.

Does the signal change when you turn the cutoff or resonance potentiometer?

I am assuming I can move on to the envelope?

I probably would move on, yes. Even if there are problems they might be easier to fix when you have a mostly working xoxbox.

I didn't check if the signal changed when I turned the cutoff or res pot.

Should I just put the whole rest of the kit together and see if it works? if not, troubleshoot from there? At this point of posting I am almost done with the envelope.

Edit: I just tested the envelope and believe it works. I got ~12V (11.88) at the north side of D35

[synth505]

Ok..so here is where I am at now.

I have completed the VCO, VCF, envelope, and the VCA. I tried the test at the end of the VCA to see if I could hear a pluck from the synth but I didn't seem to get anything. I probed the pins where VR8 will go but didn't get any sound.

Should I just keep going till the whole thing is put together or wait until I know this stuff works before moving on to the amp/headphone and the sequencer?

I have attached pics of where I am at.

[MMM]

Have you already done the second envelope test? The one at D36? If not please do so and report back.

For the VCA test you'd need the innermost pin of VR8; and of course it would be a good idea again to attach the 3V to R90 before.

[synth505]

So I am quite happy right now. I set up to do the second envelope test and the headphone test again and they both worked!

I was able to get a pulse on D36 when touched to R3, then I followed up with the headphone test and was able to trigger a note and hear it!

Short video trying it out using the Max/MSP scope~
http://www.youtube.com/watch?v=3eV4gaCmhcM

ACIDDDDDD

On to the headphone amp, mixer, and sequencer..