>Basically I was loosing amplitude of theThis 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).
> signal through the capacitor at < 5 Hz. Eventually, it would fall
> below the threshold of the transistor.
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>>>
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