X-4046 VCO Help

tehskull

Finished mine last night. Working on calibrating it now. I have only been doing DIY synths for about 3 months. This is my 4th completed module. Calibrating is going OK so far. When the VCO gets into higher octaves, it cuts off. Powering it off then on brings it back once the frequency is turned back down. Not sure if this is a characteristic of my 4046 or not (which is a motorola). The HF trimpot is set to maximum resistance per Thomas's calibration instructions. I am going to continue calibrating with tools now. However if anyone has any input it would be gratetfully appreciated. So far I am very happy with it. A very big thanks to Matthias and Thomas for this great project.

Thanks!

Andrew

vco2.jpg

Description:

Calibrating the VCO with MFOS 1v\oct calibrator.

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2.6 MB

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82 Time(s)

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vco1.jpg

Description:

Completed module

Filesize:

2.94 MB

Viewed:

87 Time(s)

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fonik · Posted: Thu Jul 14, 2011 2:02 pm Post subject:

apart from the oscillation stopping: as long as it oscillates, do you get it tuned to 1V/oct? and how many octaves do you get out of it?

tehskull · Posted: Thu Jul 14, 2011 4:00 pm Post subject:

I am getting 8 octives just fine(my 1v\oct calibrator only goes to 8 ). It cuts off when I turn the Frequency pot up. I am trying a software oscilloscope tonight to do some more checking as i do not have a hardware oscilloscope.

fonik · Posted: Fri Jul 15, 2011 1:09 am Post subject:

diablojoy · Posted: Fri Jul 15, 2011 3:14 am Post subject:

looking at the schematic if you can get 8 octaves with a CV into the 1v/oct input it does not leave much to check as the freq pot is summed to the same opamp
check +/- 15 volts either side of freq pot R43 -100k and that R29 is 100k
if all that checks OK then you do have something very strange going on.

fonik · Posted: Sat Jul 16, 2011 1:51 pm Post subject:

problem solved. he swapped the motorola for an NXP!

so the motorola does not seem to be a good choice all the time!?

bubzy · Posted: Sat Jul 16, 2011 11:39 pm Post subject:

im wondering if the motorolas i have are the problem too. just cant find NXP's anywhere. any clues?

Level5 · Joined: Feb 16, 2007 Posts: 27 Location: Germany

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