4091. I do not think it is the FET. The signal maintains a pretty constant amplitude for the entire range of the the oscillator. It is onlt AFTER the 100n coupling cap that the amplitude is lost.
Tony
________________________________> To: cgs_synth@yahoogroups.com> From: contact@...> Date: Sun, 7 Oct 2007 11:08:07 -0400> Subject: Re: [cgs_synth] Re: Bi N Tic question>> Just out of curiosity, what FET transistor are you using?> Scott> ----- Original Message -----> From: Anthony Rolando> To: cgs_synth@yahoogroups.com> Sent: Saturday, October 06, 2007 8:32 PM> Subject: RE: [cgs_synth] Re: Bi N Tic question>>Basically I was loosing amplitude of the>> signal through the capacitor at < 5 Hz. Eventually, it would fall>> below the threshold of the transistor.> This is exactly the problem I am having. I did not measure the freqency at which it is occurring, but it is definitely at a low frequency (below 20hz).> I have the rev. 1.2 board, all the component vales have been checked and re-checked. The cap measures 100n out of circuit. Another 100n does the same thing.> Like Ken said, there should be plenty of protection for the 4024 (with the 100k, the diode, pull down R). STILL, I am very curious as to what could be causing this...> I was using a metal film cap, perhaps I should be using something else???> The unit is up and 'running without the cap AND IT IS FREAKING AWESOME.> I am just curious why this was happening.> Thanx for the replies,> Tony> ________________________________> To: cgs_synth@yahoogroups.com> From: davebr@...> Date: Sat, 6 Oct 2007 14:15:46 +0000> Subject: [cgs_synth] Re: Bi N Tic question>> 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>>>> __________________________________________________________> Climb to the top of the charts! Play Star Shuffle: the word scramble challenge with star power.> http://club.live.com/star_shuffle.aspx?icid=starshuffle_wlmailtextlink_oct> [Non-text portions of this message have been removed]>
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Tony
________________________________> To: cgs_synth@yahoogroups.com> From: contact@...> Date: Sun, 7 Oct 2007 11:08:07 -0400> Subject: Re: [cgs_synth] Re: Bi N Tic question>> Just out of curiosity, what FET transistor are you using?> Scott> ----- Original Message -----> From: Anthony Rolando> To: cgs_synth@yahoogroups.com> Sent: Saturday, October 06, 2007 8:32 PM> Subject: RE: [cgs_synth] Re: Bi N Tic question>>Basically I was loosing amplitude of the>> signal through the capacitor at < 5 Hz. Eventually, it would fall>> below the threshold of the transistor.> This is exactly the problem I am having. I did not measure the freqency at which it is occurring, but it is definitely at a low frequency (below 20hz).> I have the rev. 1.2 board, all the component vales have been checked and re-checked. The cap measures 100n out of circuit. Another 100n does the same thing.> Like Ken said, there should be plenty of protection for the 4024 (with the 100k, the diode, pull down R). STILL, I am very curious as to what could be causing this...> I was using a metal film cap, perhaps I should be using something else???> The unit is up and 'running without the cap AND IT IS FREAKING AWESOME.> I am just curious why this was happening.> Thanx for the replies,> Tony> ________________________________> To: cgs_synth@yahoogroups.com> From: davebr@...> Date: Sat, 6 Oct 2007 14:15:46 +0000> Subject: [cgs_synth] Re: Bi N Tic question>> 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>>>> __________________________________________________________> Climb to the top of the charts! Play Star Shuffle: the word scramble challenge with star power.> http://club.live.com/star_shuffle.aspx?icid=starshuffle_wlmailtextlink_oct> [Non-text portions of this message have been removed]>
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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