Testing VCF issue

[biggiesmalls23]

Im upto the VCF on my x0x and i installed everything as per the instructions, doubled checked every part and tested every resistor.
I went to test the sine wave on the oscilloscope and i found i had a quite small wave going on, having to zoom right in on the scope to actually see (.2v and lower) it but whenever i turned the reso upto it didnt do anything, a bit of a subtle movement but nothing that looked like a resonant wave. The filter changed the amplitude of the sinus wave i did see.

i checked the voltage bias of the R105 for the saw wave and it was sitting at about half, 4.3v there abouts. i thought this was strange so i disconnected everything and went back to the start and tested everything to see where the issue might be. My variable power supply was giving 3v's and the power board was giving me all correct readings, the vco waves were back to normal again, 8.5v dc bias for saw and around 6.8/9v for square so i decided to test the oscilloscope again for the VCF. Before doing that i noticed that my potentiometer on VR2 (i think, it was the first potentiometer i put onto the main PCB) was a bit un aligned so i desoldered the 3 pins uptop and moved it a bit then resoldered it back.

I had everything hooked up as usual and i normally ground the scope to the 5v Regulator on the I/O board so i went to do that, the second i hit the lug with the scope ground clip it cut the power to my entire bench (kill switch flicked over). I thought this was strange, reset everything, started again, this time with the scope turned off, went to clip the ground for the probe on and again, entire bench power cut..

im sorda wondering what to do, do i try again, is the scope causing this? what else can i ground the scope on ? if im still getting the right bias outta the saw/square waves with all the VCF parts in could i move on or is this a povital test? also i noticed in the pictures that when they are testing the VCF they dont have caps C28 and the one above (cant see it in the picture, maybe C29) installed in the board, yet the VCF parts states they are to be soldered? is the potentiometer no good? i checked all my soldering and it looks fine, not sure what to test next?

[guest]

if your scope is shutting down
and the mains power outlets are going out
you should be very careful
this is most likely something wrong with your wallwart
or with the mains wiring at your bench

it sounds like the gain is a bit off in your vcf
double check the resistor values around q21
in particular r108 r110 and r111

if you havent done so yet
compare all the vcf voltages
to those listed in the voltage map

[biggiesmalls23]

hey guest, thanks for your reply.

i checked the resistors that you mentioned, all were correct, wall wart was fine, i went forward and completed the envelope, went back to the VCF and tested it again. This time i did the headphone test and on pin 6 i was able to hear the amplitude being changed via the potentiometer and once i applied some resonance it gave me a acidic tone.

I then completed the VCA and did the headphone test for the "struck note" - i wired up everything and once i struck R3 with my clip i was able to hear a note ! tried it a few times and was successful every time.

i would like to go back and test the VCF with the oscilloscope again but im pretty convinced everything is in fine, saying that because i tested everything since and all has been 100%.

[guest]

glad to hear its working
but be careful with the scope
if you were getting sparks
that means something was shorting to the mains voltage

test your wallwart
by measuring the resistance from the jack back to the plug tips
its possible that the wallwart is shorted internally
and is connecting your x0x back to the mains

did you have anything else connected to the x0x at that time

[biggiesmalls23]

it didnt spark when it cut the mains power, it just cut the power as soon as i went to ground the probe to the LM 5v Regulator, i had my variable supply grounded to the LM 5v as well, that was all.

i have another question as well, i have the TT x0x, just doing some reading about it on the forums, i noticed that when following the adafruit build it said to use 2.2uf Cap for C51 on the headphone amp build, i was given 22uf, is this a correct replacement or should i get it out of there right away and get a 2.2uf Cap?

[antto]

schematic says 2.2uF electrolytic
these TT kits seem to throw random parts in..
better double check every part you put against the adafruit buildmanual/schematic

[biggiesmalls23]

thanks for clarifying that, that has been the only part ive had incorrect, ill replace it straight away.

[biggiesmalls23]

what volt cap should i use for the 2.2uf? 50v/60v?

[antto]

the schematic says 50, but i think 60 won't hurt
http://wiki.openmusiclabs.com/wiki/x0xb ... board2.png
grab this, a more readable schematic

[biggiesmalls23]

thanks for that !

[aminoacid]

i was thinking that maybe theres a short in your probe. or ju