Here's something strange. I just hooked it up again. In cycle mode, if the
fall and rate switches are in expo mode, raising the Fall CV or Rise CV
pots will increase the freq. output up to the 12 o'clock position. Going
past that position, the freq. will decrease slightly. If the switches are
in the linear position, this doesn't happen.
Also - Changing the fall or rise switch from linear to expo will lower the
cycle mode freq. even with both CV pots at minimum.
fall and rate switches are in expo mode, raising the Fall CV or Rise CV
pots will increase the freq. output up to the 12 o'clock position. Going
past that position, the freq. will decrease slightly. If the switches are
in the linear position, this doesn't happen.
Also - Changing the fall or rise switch from linear to expo will lower the
cycle mode freq. even with both CV pots at minimum.
On Mon, Feb 11, 2013 at 8:37 PM, A S <synthasaurus@...> wrote:
> 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 <dean.lowe@...>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]