Cgs synth

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 <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]
>
>
>
>------------------------------------
>
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>
>
>
>

_______________________________________________________________________
Ken Stone sasami@... otherunicorn@...
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