Problem with vco (solved) now with vcf

[francois]

Hello,
I just finished assembling my XOXbox (WILLZYX kit) and have some problems...and no sound (sequencer seems to have problems too but we'll see later)!

So i'm trying to have the synth ok first.

Let's begin with the first section: VCO !
I can't calibrate it: tm 5 and 4 have strange behavior and now that i've acess to an oscilloscope (i haven't during assembling) i'have checked for waveforms and they 're strange looking but present at switch.

The square one have a very peaky first edge (much more than the pictures on manual), the saw don't really look like it should too: it seems to have a small shelf after the rising edge, it slopes but not very linear and their is some "garbage" just before the rising edge... to me it looks like if the end of the slope is folding on itself... They seems to be correct amplitude around 4v pk-pk(maybe a little more).

When trying to adjust tracking with TM4 (testing and calibration procedure 3 switching from 2v to 3v) it dont do anything to frequency. Adjusting tune modify pitch.
Adjusting TM5 modify the 'look'of sawtooth and square too...

Well... i'm a bit lost and don't know where to start. I've probbed with the 'scope around the vco but nothing that i note.
I don't have acess to camera now but i should be able to post pictures tomorrow.

Could you help me?

Edit 20mn later: just checked if signal is present at vcf with scope: very very weak signal as i had to change scale on scope (from 1v per division to 50mv per division)

[francois]

OK so... after rechecking the psu used for 2Vand 3V it seems to give parasitic oscillations when in circuit, so back to cell and this time, sawtooth and square looks rather good ! ...and Tm4 Tm5 have much normal behavior! Great!

I can't calibrate vco tracking for now as i miss some parts to build another cell psu and because it's very late at night (or really early in the morning it depends) and can't focused anymore... But vco is working as it should now!

So from now next step is debuging vcf section.