This is a revision 1.2 brd. Ken.
Tony
________________________________> To: cgs_synth@yahoogroups.com> From: sasami@...> Date: Sun, 7 Oct 2007 06:54:08 +1000> Subject: Re: [cgs_synth] Re: Bi N Tic question>> 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>>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> Australian Miniature Horses & Ponies>
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Tony
________________________________> To: cgs_synth@yahoogroups.com> From: sasami@...> Date: Sun, 7 Oct 2007 06:54:08 +1000> Subject: Re: [cgs_synth] Re: Bi N Tic question>> 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>>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> Australian Miniature Horses & Ponies>
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