Cgs synth

Be aware the PCB should have been corrected since Richard found that error,
so depending on the age of the PCB you have, the diode may be in the correct
position.

Ken

>I had a similar problem. Basically I was loosing amplitude of the
>signal through the capacitor at < 5 Hz. Eventually, it would fall
>below the threshold of the transistor. There is plenty of signal to
>clock the 4024, it's just at the wrong level. I replaced that circuit
>with a two resistor and diode clamp to clock the 4024 directly.
>Details are at
>http://modularsynthesis.com/cgs/cgs.htm
>
>Yours sounds similar, but different in that it stops at a higher
>frequency.
>
>Later, Richard Brewster posted a message for a similar problem: "I am
>finishing mine, finally. I found an error in the clock coupling
>circuit etch. The diode that is supposed to clamp the voltage on the
>transistor base is not connected to the base of the transistor, but
>rather to the opposite end of the 100K series input resistor. I fixed
>this (cut the connection to the non-grounded end of the diode and put
>a jumper to the correct spot). I also DC-coupled (omitted the 100nf
>cap) that delivers the ramp out of the VCO."
>
>That might have fixed mine but I never tried it. Richard also posted
>another message about an error on the damping potentiometer wiring
>diagram.
>
>Dave
>
>--- In cgs_synth@yahoogroups.com, Anthony Rolando <goldenechos@...>
>wrote:
>>
>>
>> Hello, just finished building the Bi N Tic filter/ osc. and I have a
>couple of questions.
>>
>> I was getting quite a bit of slop on the Frequency panel control. It
>basically only worked from about 12:00 on...
>>
>> I traced this down to the 100n cap between pin 6 of the 3140 and the
>100k that is connected to the base of the BC547`(of the collector is
>connected to the CD4024).
>>
>> What was happening is that once the VCO went below a certain
>frequency, the Saw wave would all but disappear AFTER the 100n cap. It
>was a good signal at pin 6 of the 3140. The collect of the BC547 was
>just setting at 7V when the frequency was set to (or beyond) this low
>point.
>>
>> I was able to rectify the situation (I think) by bridging the 100n.
>With the 100n out of circuit I get good strong oscillations for the
>entire range of the Freqency Panel control. The filter sonds really
>cool.
>>
>> Any insight as to what might be happening would be greatly
>appreciate. I do not like the idea of removing something from the
>circit design in order to get it to work.
>>
>> Thanx,
>>
>> Tony
>> _________________________________________________________________
>> Help yourself to FREE treats served up daily at the Messenger Café.
>Stop by today.
>> http://www.cafemessenger.com/info/info_sweetstuff2.html?
>ocid=TXT_TAGLM_OctWLtagline
>>
>
>
>
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>
>Yahoo! Groups Links
>
>
>
>

_______________________________________________________________________
Ken Stone sasami@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>