Cgs synth

>I am just curious why this was happening.

It probably comes down to the one significant variable in the area- the gain
of the transistor. Perhaps you have one with poor gain, where as I was
testing one with exceptional gain, the difference between the two extremes
thus not being allowed for in my design.

If the 100n is put back in circuit, and the resistor in series is reduced to
47k or 33k, what happens then?

Ken

>
>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>>
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