Sound slowly transforming into clicks

[VerreyckenGerd]

Hi all,

I have built a kit from x0xsh0p Germany and it worked fine for many hours.

Then at one day it started sounding more and more filtered until nothing but clicks remained on the highest knob settings.
Cutoff frequency seemed to sponainiously drift towards nothing in a very instable way. (a little clickling and cracking here and there)
After powering of the machine and rebooting it the sound was kind of back for a minute or so and trouble reappeared.

I checked the box for cold joints but couldn't find anything then the sound came back slowly and the unit worked fine for many hours again....

This has happened a few times now in a row the analog part seems to die and heal itself.
Something running hot? Faulty semiconductor, some capacitor electrolising inside?

Anyone know how to measure the filter control voltage? or is it controlled by current like the BA6110?

I do not have any spare BA6110's or filter transistors in stock to play with.

Gonna probe out some voltages the next days iI guess....

Anyone else had this dropping filter/amp problem?

Greetings,

Gerd

[VerreyckenGerd]

Update:

Today I have measured a constant 8 volts behind resistor R62.
This is the VFC side of the DC coupling between VCO and VCF.

Should this voltage not be 5.333?

From there the signal seems to disappear.

Greetings,

Gerd

[antto]

at R62 that's basically right after the waveform switch (vco output)
the sawtooth should oscillate between ~ 11V and 5V somewhere
while the square wave won't go below the 5.333V (and is slightly quieter)

but if you don't pick any oscillation at that point - there's something wrong with the vco

[VerreyckenGerd]

Thanks for the help man, but the problem is not the vco my scope measures both waveforms perfectly until the selected waveform passes R62. After R62 (filterside) there is only 8V constant. Is the waveform converted to a variable current waveform with constant voltage or something?

ps today the unit worked for another 10 minutes afted COLD start
The filter doesnt sound stable from the beginning and the filter seems to fade out first afterwards the volume of the remaining deep basses fade out until you hear nothing but clicks from the gate and accent.

Worst thing about it is that i dont understand the filter part.I am more speciallized in programming electronics for production automation.

eny help would be wonderfull

Greetings x0xers















signaml

[VerreyckenGerd]

Thanks for the help man, but the problem is not the vco my scope measures both waveforms perfectly until the selected waveform passes R62. After R62 (filterside) there is only 8V constant. Is the waveform converted to a variable current waveform with constant voltage or something?

ps today the unit worked for another 10 minutes afted COLD start
The filter doesnt sound stable from the beginning and the filter seems to fade out first afterwards the volume of the remaining deep basses fade out until you hear nothing but clicks from the gate and accent.

Worst thing about it is that i dont understand the filter part.I am more speciallized in programming electronics for production automation.

eny help would be wonderfull

Greetings x0xers















signaml

[MMM]

Thanks for the help man, but the problem is not the vco my scope measures both waveforms perfectly until the selected waveform passes R62. After R62 (filterside) there is only 8V constant. Is the waveform converted to a variable current waveform with constant voltage or something

The important thing is to measure everything in the filter part with an AC coupled scope. The voltages are very small but travel on top of a significant DC bias (we're talking signal voltages under 100mV).

The 8V DC are ok but you need to check the AC part on top of it. Then trace it through the filter ladder, measuring C18, C19, C24, C26. The signal will get progressively weaker through the ladder (and softer, depending on the position of the cutoff control). You may also want to measure the DC offset on those caps.

[synthplayer]

The signal amplitude is very low in the filter ladder and not easy to observe, it might be worth looking at the output of the VCF to verify whether it actually works first. To check VCF for output, look at Q19 pin 1 or node R96 connects to C14.

[VerreyckenGerd]

Thanks Synthplayer for your advice.

Next time the x0x does it again ill have a listen to that signal between VCF and VCA.
At the moment my x0xd works fine and the problem doesnt seem come back.
Not even after many hours of looping the same sequence.

The last time the problem started after hooking up a Ibanez TS-09 on the mix output.
Coincedence or not, I dont know....

To be continued...

Greetings
Gerd