The J108 works great. I have built four of Ken's VCOs and they all work
perfectly. (I use a few different resistor values in the control and
output circuits, but the VCO core is the same.) See:
http://www.pugix.com/cgs-vco.htm
Here are two possible problems. Either the VCO is not oscillating, or
the output isn't being coupled into the 4024 counter correctly. First
check if you have a 5 volt high sawtooth at pin 6 of the CA3140. If you
do then it is oscillating. If that is OK, then check the 4024 for
square waves on pins 9, 11, 12. If they are not present, something is
amiss with the coupling circuit. On the Bi-N-Tic board I got, the
1N4148 diode was hooked to the wrong end of the 100K resistor by the
etch. It should go to the base of the transistor (as on the
schematic). I corrected this. If connected to the other end, the diode
could impact the FET switching properly, I believe. Ken?
-Richard Brewster
http://www.pugix.com
kopernig wrote:
perfectly. (I use a few different resistor values in the control and
output circuits, but the VCO core is the same.) See:
http://www.pugix.com/cgs-vco.htm
Here are two possible problems. Either the VCO is not oscillating, or
the output isn't being coupled into the 4024 counter correctly. First
check if you have a 5 volt high sawtooth at pin 6 of the CA3140. If you
do then it is oscillating. If that is OK, then check the 4024 for
square waves on pins 9, 11, 12. If they are not present, something is
amiss with the coupling circuit. On the Bi-N-Tic board I got, the
1N4148 diode was hooked to the wrong end of the 100K resistor by the
etch. It should go to the base of the transistor (as on the
schematic). I corrected this. If connected to the other end, the diode
could impact the FET switching properly, I believe. Ken?
-Richard Brewster
http://www.pugix.com
kopernig wrote:
> hi all,
> i've put a bi-n-tic filter together recently. the filter section seems
> to be working - it definitley filters an input signal, but otherwise
> there's not a peep out of it. cv, fm have no effect. i'm 99 percent
> sure everything's where it should be...
> i bought the filter as a kit from laurie at elby designs, and the jfet
> was a j108, which i swapped for a 2n5457 (on a whim,really). anyone
> have any experience with this? any parts more prone to failure than
> others?
> thanks,
> andrew.
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> The CGS Modular Synth home page: http://www.cgs.synth.net/
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