Range clicks on xoxbox

[MMM]

Thinking out loud a bit:

The whole thing happens when the voltage at the connection of thermistor, R106, R118 and Q26 is above a certain value. Since the CV coming from the keyboard/sequencer seems to be ok this either leaves the voltage coming from the tuning knob itself or something else altogether.
It would be nice to learn if the oscillator itself is malfunctioning (which is what I'm suspecting) or if there is some other breakdown down the line.

[Zemky]

Well the digital sequencer is ok I checked the midi in my Daw.

In my video I show how the higher notes of the vco are not played instead of that i just can hear clicks, in all modes. Doeesnt matter if I turn the tune knob or play high notes with the sequencer. So must be the analog part..

Yesterday I tried to turn it on and hear mix out with my
Headphones, I could hear signal but very low and just with the VCF opened, the cliks
Were just like the attack of the regular notes

[aminoacid]

could you see if you can get a new one or get it fixed from the store you bought it from?


if not, do you have multimeter and/or scope and know how to use it some?

[Zemky]

I'll try, now im using my x0xb0x as midi sequencer for my mopho :S

[Zemky]

I opened the x0x again to take a look in Q26, is really weird because Q26 is bended and there is no R100A and no R100B.

on Q26 that is bended as I said and make contact with the board (on R100A btw) there´s a C1583 92 (F,R???)

I was reading the wiki and I saw theres a couple of resistors in there.... :S

[Zemky]

I took some pics of VCO...to make it easier,as you can see nothing on R001a and R001b and bended transistor, can be that the source of all problems with VCO pitch?

[Nikkel]

If i look close to the spots where the thermistors are supposed to be...
i think that i can see pads in the middle, like your thermistors
are on the back and probably surface mounted.

correct me if i'm wrong!

[Zemky]

no; theres no thermistor under the cutoff knob fu*** I was cheated; I traded my sampler for this x0x

[MMM]

Yes, there's probably an SMD thermistor underneath Q26; and Q26 is probably bent to get it closer to that thermistor. At lest that's what I would expect here.

I think without measurements this is very difficult to debug. Zemky, do you have access to a multimeter or an oscilloscope? Maybe you could borrow one for the weekend or so?

[MMM]

no; theres no thermistor under the cutoff knob fu*** I was cheated; I traded my sampler for this x0x

Not under the cutoff knob: Bend back Q26 a little bit and look there. The SMD thermistor will NOT look like a regular resistor/thermistor.

[Zemky]

Ok guys, I bended the resistor and I saw a small squared piece between the middle pins of R100A (I dont know what is it, 1 thermistor maybe; As I can see there´s a 33 on that).

The bended resistor was touching the small squared piece and there was some kind of white residue there.





Ill have to check the scope and all that stuff; I have no idea about electronics and i´ll have to ask for some help around here.

[Nikkel]

The white residue is probably some thermal paste.
But you found the thermistor!
I can't tell if it's the right component by the way but someone else will be able.

[MMM]

Yes, that's the thermistor - and it's the same as on my own xoxbox; so I guess it should work anyway.

I'll do some experimenting and see what I can come up with.

[MMM]

So far I haven't been able to reproduce/simulate a similar behaviour over here.

More food for thought: If the chip on the IOboard is socketed as well it might be possible to swap IC23 from the IOboard with IC11 from the mainboard and see if that changes anything.

If I'm not mistaken C62 is a ceramic cap in the picture which indeed points to this being a TT machine (I don't think Mode Machines ever installed sockets for ALL chips).

[Zemky]

Thanks for your help guys I'll take a look when I arrive home , cheers