Old x0x never been tuned (solved)
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Re: Old x0x never been tuned

by pulsar256 on Fri Apr 12, 2013 12:58 pm

isak wrote:Yes, the sequencer is fine.
Everything is working fine except the midi in.

That rules out the DAC.

isak wrote:More strange things just came up...
The the decay is not working as it should, it's working but very weak not as strong as it use to be.
It's getting out of tune the next day, strange, isn't it?
Only moving tm5 just a bit and it's in tune again.


These are very crazy symptoms. Seems something is happening to the MIDI-In signal as it travels down to the uC. It's difficult to check that without a scope. The other symptoms you are having... No idea. Really. Only a vague feeling that some shorts / bad (or wrong valued/mounted) caps end plenty other components could cause that. Let's hope someone more experienced can point you in the right direction.

But then again... You mentioned your reference 5.333 voltage to be drifting a tiny bit. And now it sounds like you need to touch a trimming pot to push the system back into balance? It *could* be related to some oscillation in the voltage regulators - but this is way out of my league.
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Re: Old x0x never been tuned

by antto on Fri Apr 12, 2013 4:42 pm

instead of touching TM5, you should have measured your 5.333 voltage
because if you had it calibrated to 5.333V and then tuned the VCO - then the 5.333 line drifted away <- THAT's why your vco got detuned, and you should have just readjusted the 5.333 line, then figure out why it "moves"

hope this helps
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Re: Old x0x never been tuned

by pulsar256 on Fri Apr 12, 2013 5:29 pm

Perhaps you could hook up the quirky x0xb0x to the IO Board of the good one? Smells like a power issue.
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Re: Old x0x never been tuned

by isak on Fri Apr 12, 2013 5:49 pm

Thanks guys.

After the drift I measure j4 and it was moving from 5.33 to 5.32, I think it's a power supply issue, what do i need to check?
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Re: Old x0x never been tuned

by isak on Sat Apr 13, 2013 4:23 am

ok, i connected only the I/O board to the power supply.
i measure 5.32V when turning it on, after 5 min or so it was 5.33V.
i dont recall in any x0xb0x i ever own that i was needed to wait that things will worm up :?
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Re: Old x0x never been tuned

by isak on Sun Apr 14, 2013 5:27 am

Hi guys

can you maybe confirm that it's the same with your I/o board?
Can anyone check this for me please with good working x0x?
I only need to know that if you power up only the I/o board you get 5.32V from j4 and after 5min or so it's raising again to 5.33V.

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Re: Old x0x never been tuned

by pulsar256 on Sun Apr 14, 2013 6:14 am

A drift of 0.01V does not sound much too me. Without using a precise multimeter it's difficult to tell. On my Fluke I'm getting 0.002V drift - but I believe this might be even within the tolerance of the multimeter itself.
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Re: Old x0x never been tuned

by isak on Sun Apr 14, 2013 8:15 am

So as I understand from you this is not a problem at all and not suppose to drift?
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Re: Old x0x never been tuned

by pulsar256 on Sun Apr 14, 2013 10:09 am

Might be a symptom of something else. You can rule out (or verify) the power supply as the source of your MIDI / decay problems by transplanting temporarily the IO board from the "good" x0xb0x.
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Re: Old x0x never been tuned

by antto on Sun Apr 14, 2013 11:56 am

yes. a drift between 5.32 and 5.33 is small, it could be even rounding error in the multimeter
We are here too: irc.freenode.net >>> #x0xb0x
..:: c0nb0x v1.00 ::.. http://forums.adafruit.com/viewtopic.php?f=7&t=29282 (new control app - win/osx)
VCO Tuning: http://forums.adafruit.com/viewtopic.php?f=12&t=24759 (do it the EASY way)
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Re: Old x0x never been tuned

by MMM on Sun Apr 14, 2013 12:46 pm

...and it also won't affect the tuning significantly.
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Re: Old x0x never been tuned

by isak on Mon Apr 15, 2013 2:16 am

ok, i think i fix it now.
i replaced the second Tempco, i thought that they should be from the same series, after tuning it on it was ok :)

moving on to the decay...
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Re: Old x0x never been tuned

by isak on Fri Apr 19, 2013 11:52 am

Ok, Tune is fix after replacing the 2 Tempcos.
Decay is fixed, don't know how I fixed it but I did.
After replacing the 7805 on the I/o board the decay started to work ok, streange, isn't it?

What got left is the midi in, after checking so many things I don't know what to do next.
Replace ic9, replace the MC, checked the resistance from pin 10 of the MC to q50 and r15, it shows -0.004 ohm.
Where to now?

Cheers.
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Re: Old x0x never been tuned

by pulsar256 on Sat Apr 20, 2013 7:05 am

Check if both rotary encoders are working properly. They share the same 4-Bit bus to the uC while the readout is being determined by Q5/R255/R254. So verify that you can actually put the system into MIDI-IN mode. Check every Data-Line from the right encoder down to the uC. Also Check the Diodes D3 - D10 for proper orientation and for a voltage drop of around 0.6V.
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Re: Old x0x never been tuned

by MMM on Sat Apr 20, 2013 6:41 pm

Another possibility:

The signal coming from the IOboard is too weak. The situation as I see it is as follows: The MIDI input on the IOboard isolates and "reconditions" the MIDI signal; something similar is done in every MIDI device. I could imagine that the signal after this part is not sufficient to "drive" the appropriate processor pin - but it could be sufficient to drive another MIDI input stage (where it would get "reconditioned") again.

I guess the best way to find out would be to check at the processor pin with an oscilloscope.
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