Thanks Dean. I just measured the voltages. With a decreasing input (slowly
decreasing from +5V to 0V), Pin 5 of the TL072 follows the input until the
input drops into the 10s of Millivolts. Decreasing the input lower causes
the voltage at Pin 5 to immediately jump to +3.74 volts. I disconnected the
input voltage patch cord, but the +3.74 volts is still there. I'll try
replacing the diode now to see what that does.
Thanks!
Andrew
decreasing from +5V to 0V), Pin 5 of the TL072 follows the input until the
input drops into the 10s of Millivolts. Decreasing the input lower causes
the voltage at Pin 5 to immediately jump to +3.74 volts. I disconnected the
input voltage patch cord, but the +3.74 volts is still there. I'll try
replacing the diode now to see what that does.
Thanks!
Andrew
On Mon, Feb 11, 2013 at 9:42 PM, goldencardigan <dean.lowe@...>wrote:
> **
>
>
> Hi Andrew,
>
> Please ignore my last rant, it wasn't aimed at you in anyway.
>
> It looks like you've got your pot wiring right. Check the Diode connected
> to Pin 5 of the TL072, next to the two 220k Resistors on the schematic.
> With nothing connected to the Trig or Input, you should have voltage
> present on the tranny side of the Diode, but no voltage on the side
> connected to the TL072. If there is voltage passing from the tranny through
> the diode, it means the diode needs to be replaced. I had a similar problem
> with my build, although the symptoms seem to be a bit different. If you do
> a search you should find my previous posts regarding this.
>
> If you haven't already, check out Tim Stinchcombes page on the VCS
>
> http://www.timstinchcombe.co.uk/index.php?pge=vcs
>
> Cheers
> Dean
>
>
> --- In cgs_synth@yahoogroups.com, sasami@... wrote:
> >
> > Re locking up, have you seen the modification to replace the 10n caps
> with
> > 1n in the cycle switching circuit? 150k also go down to 100k.
> >
> > Ken
> >
> > >Hi Dean,
> > > Thanks very much for the reply. Regarding EG operation, I'm okay with
> the
> > >fact that the pots will work "in reverse" if wired with cycle mode's
> audio
> > >freq. in mind.
> > >
> > > Speaking of cycle mode, it does work as an oscillator in this mode,
> though
> > >I'm not sure if it works in the correct range. If I move the pots
> clockwise
> > >to a high freq. extreme, it will lock up. I have to toggle the cycle sw.
> > >off and on to make it work again.
> > >
> > > I'm ohming the pots out as I type this. CW and CCW is referenced
> viewing
> > >the pot from the front (shaft towards you). They are wired like this:
> > >
> > > Rise pot:
> > >CW - Gnd
> > >CCW - +15V
> > >Wiper - RRW
> > >
> > >Fall Pot:
> > >CW - Gnd
> > >CCW - +15V
> > >Wiper - FRW
> > >
> > > Rise CV:
> > >CW - RCCW
> > >CCW- RCW (GND)
> > >Wiper - RW
> > >
> > >Fall CV:
> > >CW - FCCW
> > >CCW- FCW (GND)
> > >Wiper - FW
> > >
> > >
> > >The odd thing is that FCW and RCW are at ground reference, so that
> should
> > >be the CCW pot terminal, not CW. Unless I'm confusing myself... is the
> > >silkscreen wrong for these two?
> > >
> > > Thanks again,
> > > Andrew
> > >
> > >
> > >
> > >
> > >
> > >
> > >On Mon, Feb 11, 2013 at 3:38 PM, goldencardigan wrote:
> > >
> > >> **
> > >>
> > >>
> > >> Hi A S
> > >>
> > >> To me it sounds like you need to check your pot wiring. Have another
> read
> > >> of the wiring list and confirm your connections, as a lot of people
> have
> > >> had problems with this. Can you tell us which connections you have
> used for
> > >> the Rise, Fall and respective rate pots.
> > >>
> > >> Just for the record, I also want to address the claim on the 'mods'
> page
> > >> you listed below that the Rise and Fall connections are reversed. The
> VCS
> > >> is in a way an Attack/Release Envelope with a looping function. If
> you give
> > >> it a trigger it will respond accordingly and the Rise will control the
> > >> attack time exactly like any other envelope (the Fall acting like the
> > >> release control). Now if you engage the looping feature, yes the Rise
> and
> > >> Fall pots do seem to be reversed if you compared it to a LFO. But it
> does
> > >> work exactly like every other envelope with a looping feature. As the
> > >> attack and release times of the envelope decrease, the quicker the
> > >> oscillations get.
> > >>
> > >> IMHO I always try to build my boards as per the designers notes and
> make
> > >> any mods after verifying the board is working as intended. If I do
> have any
> > >> probelms with the board I can gaurantee that it is a mistake I have
> made
> > >> and not due to a mod that I have installed.
> > >>
> > >> Sorry, I'll get off my soap box now. Double check your wiring and let
> us
> > >> know how you go.
> > >>
> > >> Cheers
> > >> Dean
> > >>
> > >>
> > >> --- In cgs_synth@yahoogroups.com, A S wrote:
> > >> >
> > >> > Hello,
> > >> > I have a CGS75 Rev 0.0 where the Rise and Fall pots don't give
> typical EG
> > >> > slew rates.
> > >> >
> > >> > For the following symptoms, I'm using a square wave output from an
> LFO
> > >> set
> > >> > about 1 Hz to the input of the VCS. The output of the VCS is
> driving a
> > >> VCO
> > >> > FM input, so that I can hear what the output of the VCS is doing.
> > >> >
> > >> > 1. The VCS outputs the input LFO signal pretty much unaffected if
> the
> > >> rise
> > >> > and fall pots are at the 9 o'clock position. If I lower either the
> fall
> > >> or
> > >> > rise pot to minimum, there is a small amount of slew for each
> function.
> > >> >
> > >> > 2. If I raise either (or both) pots from the 9 o'clock position, it
> > >> doesn't
> > >> > do anything different up to the 12 o'clock position.
> > >> >
> > >> > 3. If I increase the rise pot further (with the fall pot at 12
> noon),
> > >> > there is a positive dc offset added to the LFO input as the pot
> level is
> > >> > increased. There is no slew.
> > >> >
> > >> > 4. Conversely, if I increase the fall pot further (with the rise
> pot at
> > >> 12
> > >> > noon), there is a negative dc offset added to the LFO input as the
> pot
> > >> > level is increased. There is no slew.
> > >> >
> > >> > I added the mods mentioned on this page:
> > >> >
> http://electro-music.com/forum/viewtopic.php?highlight=cgs75&t=54330
> > >> >
> > >> > and on the CGS page:
> > >> > http://www.cgs.synth.net/modules/cgs75_vcs.html
> > >> >
> > >> >
> > >> > Here are some of the check I've done....
> > >> >
> > >> > I tried replacing the TL074, and have checked the resistor values,
> > >> > orientation of diodes, and transistors. All parts seem to be correct
> > >> after
> > >> > double checking them. I've also checked the board for solder
> shorts, and
> > >> > have ohm'd out many of the traces from component to component.
> > >> >
> > >> > I checked the voltage at the base of the 2n3904 and 2n3906 (from
> the rise
> > >> > and fall circuits). The range as I turn the pots is from 0V min. to
> 384mV
> > >> > max.
> > >> >
> > >> > I input a manually adjusted CV at the gate input. The TL072 Pins 5
> and 6
> > >> > follow the gate input. Pin 7 outputs 477 mV no matter what the gate
> input
> > >> > voltage is. There is still 477mV if I disconnect the input cable.
> > >> >
> > >> > Any help would be appreciated, and I can send pics of the PCB if
> that
> > >> > would help.
> > >> >
> > >> > Thanks,
> > >> > Andrew
> > >> >
> > >> >
> > >> > [Non-text portions of this message have been removed]
> > >> >
> > >>
> > >>
> > >>
> > >
> > >
> > >[Non-text portions of this message have been removed]
> > >
> > >
> > >
> > >------------------------------------
> > >
> > >The CGS Modular Synth home page: http://www.cgs.synth.net/
> > >Yahoo! Groups Links
> > >
> > >
> > >
> > >
> > __________________________________________________________
> > Ken Stone sasami@... otherunicorn@...
>
> > Modular Synth PCBs for sale
> > Australian Miniature Horses & Ponies
> >
>
>
>
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