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Broken x0x due to input mistake

PostPosted: Wed Oct 15, 2014 12:30 pm
by mrglf
It seems that I'm the only one in the forum who doesn't read the manual carefully.

I was showing my x0x to my friends when I plugged a standard CV signal into the pin 5 of the jumper 3, which it's the Cuttoff Control In (digital control line for setting the cut- off frequency. A high level signal sets the cut-off to its maximum value, and a 0V signal returns control to the CUTOFF pot.) I used this cuttoff input many time ago so I forgot that it was only digital. Now the filter seems to have a kind of long attack envelope and the output sound distorted... I can post an audio file if it can help to see what is happening.

I've seen that this point is directly connected into the pin 3 of the CD40109B and maybe this is the problem. I can replace it without problem, or any other component.. Can anyone on the forum make a diagnostic? It would be great to know if there's any way to make it work as before!


Re: Broken x0x due to input mistake

PostPosted: Wed Oct 15, 2014 1:02 pm
by guest
measure the powersupply voltages, to make sure 5V, 12V, and 5.333V are still doing the right things.

if they are, remove the CD40109 and see if the problem goes away, if not, remove U6 (4066) and see if it goes away.

its probably just the CD40109, and its either shorted internally and pulling the powersupply rails down, or its harmed the 4066/turned on all of its channels, so accent is on and decay is really long. do notes play after the gate is pulled low?

Re: Broken x0x due to input mistake

PostPosted: Wed Oct 15, 2014 1:10 pm
by guest
also, you can put a 10k resistor in series with those inputs to limit current inrush. that should protect it for any future mishaps.

Re: Broken x0x due to input mistake

PostPosted: Wed Oct 15, 2014 3:21 pm
by mrglf
thanks for the answer!

I have at J4 12,3V and 5,54V. Gate times and notes seems to work fine.

But I've noticed about 2 new things:

-Having set the cutoff at max, when I play any note sounds like if the cutoff is at the 70%, if I play it repeatedly fast the cuttoff starts to increase until it goes max (the real knob position, it's like a 2sec. attack), then if I stop playing for a while and press any note the cuttoff is at that 70% again.

-If I start to increase the volume, there's a point where it stops raising and then saturate even if I still turning the volume knob up.

One of my friends who came to see my x0x has another disassembled x0x (I'm recommending it to everyone I know ) so I'll compare their sounds as soon as he finish his one. I'll start with the CD40109B and see what happens!

Many thanks for your help!

Re: Broken x0x due to input mistake

PostPosted: Wed Oct 15, 2014 11:15 pm
by guest
does turning the cutoff knob change the cutoff frequency much?

the accent circuit raises the cutoff slowly over time, so it still sounds like the accent is stuck on, and cutoff is stuck on. does the output sound fine until volume is raised? this is the only thing that is odd to me. if it sounds wierd, and gets louder and eventually distorts as volume is raised, that would make sense. but, if it sounds ok, and then gets louder and eventually distorts, that means something is wrong in the mixer circuit, or maybe VCA if the volume is generally louder than it should be. what else do you have it connected to? is the ouptut going to an amplifier, or is it straight out?

Re: Broken x0x due to input mistake

PostPosted: Fri Oct 17, 2014 4:33 pm
by mrglf
Yes, the cutoff changes with the knob but if I set it to the max, it still have some cutoff and behaves like I've explained before.

I think it would be better if I compare my x0x with the one of my friend to see exactly which are the differences because now I'm already used to its new sound. :l

What does the CD40109 exactly do/control in the x0x? Just for curiosity.

I'll be back after testing both x0xs! Thank you again!

Re: Broken x0x due to input mistake

PostPosted: Sat Oct 18, 2014 5:01 pm
by guest
the CD40109 is just a level shifter that is used to interface outside digital signals to control the CD4066 analog switches that set cut-off, accent, decay, and env-mod.