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CGS75 VCS Slew Rate Problem

CGS75 VCS Slew Rate Problem

2013-02-11 by A S

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]

Re: CGS75 VCS Slew Rate Problem

2013-02-11 by goldencardigan

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
Show quoted textHide quoted text
--- 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]
>

Re: CGS75 VCS Slew Rate Problem

2013-02-12 by A S

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
Show quoted textHide quoted text
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]

Re: CGS75 VCS Slew Rate Problem

2013-02-12 by A S

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.
Show quoted textHide quoted text
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]

Re: CGS75 VCS Slew Rate Problem

2013-02-12 by cg_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
Show quoted textHide quoted text
>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]
>
>
>
>------------------------------------
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>Yahoo! Groups Links
>
>
>
>
_______________________________________________________________________
Ken Stone sasami@... otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: CGS75 VCS Slew Rate Problem

2013-02-12 by A S

Hi Ken,
Sure did. I used 100K resistors there, and I used this for the two 1n caps:

http://www.mouser.com/ProductDetail/EPCOS/B32529C102K/?qs=sGAEpiMZZMv1cc3ydrPrF1iYn56hZ3YmhsEj8dPJEuE%3d

Thank you,
Andrew
Show quoted textHide quoted text
On Mon, Feb 11, 2013 at 9:06 PM, <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 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]
> >
> >
> >
> >------------------------------------
>
> >
> >The CGS Modular Synth home page: http://www.cgs.synth.net/
> >Yahoo! Groups Links
> >
> >
> >
> >
> __________________________________________________________
> Ken Stone sasami@... otherunicorn@...
> Modular Synth PCBs for sale http://www.cgs.synth.net/>
> Australian Miniature Horses & Ponies http://www.blaze.net.au/~sasami/>
>
>
>


[Non-text portions of this message have been removed]

Re: CGS75 VCS Slew Rate Problem

2013-02-12 by A S

Show quoted textHide quoted text
On Mon, Feb 11, 2013 at 9:28 PM, A S <synthasaurus@...> wrote:

> Hi Ken,
> Sure did. I used 100K resistors there, and I used this for the two 1n
> caps:
>
>
> http://www.mouser.com/ProductDetail/EPCOS/B32529C102K/?qs=sGAEpiMZZMv1cc3ydrPrF1iYn56hZ3YmhsEj8dPJEuE%3d
>
> Thank you,
> Andrew
>
>
> On Mon, Feb 11, 2013 at 9:06 PM, <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 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]
>> >
>> >
>> >
>> >------------------------------------
>>
>> >
>> >The CGS Modular Synth home page: http://www.cgs.synth.net/
>> >Yahoo! Groups Links
>> >
>> >
>> >
>> >
>> __________________________________________________________
>> Ken Stone sasami@... otherunicorn@...
>> Modular Synth PCBs for sale http://www.cgs.synth.net/>
>> Australian Miniature Horses & Ponies http://www.blaze.net.au/~sasami/>
>>
>>
>>
>
>


[Non-text portions of this message have been removed]

Re: CGS75 VCS Slew Rate Problem

2013-02-12 by goldencardigan

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
Show quoted textHide quoted text
--- 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
>

Re: CGS75 VCS Slew Rate Problem

2013-02-12 by A S

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
Show quoted textHide quoted text
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
> >
>
>
>


[Non-text portions of this message have been removed]

Re: CGS75 VCS Slew Rate Problem

2013-02-12 by A S

Okay, I replaced the diode and with no input, the voltage at Pin 5 of the
TL072 is +4.2V. I also tried replacing the TL072, but still get the same
results.

Andrew
Show quoted textHide quoted text
On Mon, Feb 11, 2013 at 10:04 PM, A S <synthasaurus@...> wrote:

>
> 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
>
>
>
> 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
>> >
>>
>>
>>
>
>


[Non-text portions of this message have been removed]

Re: CGS75 VCS Slew Rate Problem

2013-02-12 by A S

I measured the cathode voltage of the diode. It's at +15V while an input
voltage is present. If the voltage is lowered to near zero (when Pin 5 goes
up to +4.2V), the cathode drops to +11V.
Show quoted textHide quoted text
On Mon, Feb 11, 2013 at 10:23 PM, A S <synthasaurus@...> wrote:

>
> Okay, I replaced the diode and with no input, the voltage at Pin 5 of the
> TL072 is +4.2V. I also tried replacing the TL072, but still get the same
> results.
>
> Andrew
>
>
> On Mon, Feb 11, 2013 at 10:04 PM, A S <synthasaurus@...> wrote:
>
>>
>> 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
>>
>>
>>
>> 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
>>> >
>>>
>>>
>>>
>>
>>
>


[Non-text portions of this message have been removed]

Re: CGS75 VCS Slew Rate Problem

2013-02-12 by cg_synth

Expo mode is feeding a changing voltage back into the unit. There will be
some change in it's frequency as a result.
Show quoted textHide quoted text
> 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.
_______________________________________________________________________
Ken Stone sasami@... otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: CGS75 VCS Slew Rate Problem

2013-02-12 by A S

Good catch! I think I might have a 22n cap at home. I'll try it tonight.

Thanks!
Andrew
Show quoted textHide quoted text
On Tue, Feb 12, 2013 at 12:55 AM, <sasami@...> wrote:

> **
>
>
> I looked at the photos.
>
> Looks like a 22pF where you should have a 22nF (0.022uF) next to TL072.
> Other side of TL072 - pin 7 resistor should be 8k2, not 22k as marked on
> the
> PCB.
>
> Ken
>
>
> __________________________________________________________
> Ken Stone sasami@... otherunicorn@...
> Modular Synth PCBs for sale http://www.cgs.synth.net/>
> Australian Miniature Horses & Ponies http://www.blaze.net.au/~sasami/>
>
>
>


[Non-text portions of this message have been removed]

Re: CGS75 VCS Slew Rate Problem

2013-02-13 by A S

Thanks to Dean and Ken for helping me get my VCS issue resolved. Ken, that
22pF cap was the culprit! Thanks for spotting that.

I noticed that the Exp/Lin switches don't have an effect unless the CV
pots are at something other than zero. Even with no external CV plugged in.
That looks to be correct according to the schematic.

Anyway, now I want another VCS! Great module!

Thanks again for taking the time to help a lost soul. :-)

Andrew
Show quoted textHide quoted text
On Tue, Feb 12, 2013 at 12:55 AM, <sasami@...> wrote:

> **
>
>
> I looked at the photos.
>
> Looks like a 22pF where you should have a 22nF (0.022uF) next to TL072.
> Other side of TL072 - pin 7 resistor should be 8k2, not 22k as marked on
> the
> PCB.
>
> Ken
>
>
> __________________________________________________________
> Ken Stone sasami@... otherunicorn@...
> Modular Synth PCBs for sale http://www.cgs.synth.net/>
> Australian Miniature Horses & Ponies http://www.blaze.net.au/~sasami/>
>
>
>


[Non-text portions of this message have been removed]

Re: CGS75 VCS Slew Rate Problem

2013-02-13 by goldencardigan

Great to hear you've got it working!

I know from my own experiences how much heartache troubleshooting a PCB can cause.

Cheers
Dean
Show quoted textHide quoted text
--- In cgs_synth@yahoogroups.com, A S wrote:
>
> Thanks to Dean and Ken for helping me get my VCS issue resolved. Ken, that
> 22pF cap was the culprit! Thanks for spotting that.
>
> I noticed that the Exp/Lin switches don't have an effect unless the CV
> pots are at something other than zero. Even with no external CV plugged in.
> That looks to be correct according to the schematic.
>
> Anyway, now I want another VCS! Great module!
>
> Thanks again for taking the time to help a lost soul. :-)
>
> Andrew
>
>
>
> On Tue, Feb 12, 2013 at 12:55 AM, wrote:
>
> > **
> >
> >
> > I looked at the photos.
> >
> > Looks like a 22pF where you should have a 22nF (0.022uF) next to TL072.
> > Other side of TL072 - pin 7 resistor should be 8k2, not 22k as marked on
> > the
> > PCB.
> >
> > Ken
> >
> >
> > __________________________________________________________
> > Ken Stone sasami@... otherunicorn@...
> > Modular Synth PCBs for sale http://www.cgs.synth.net/>
> > Australian Miniature Horses & Ponies http://www.blaze.net.au/~sasami/>
> >
> >
> >
>
>
> [Non-text portions of this message have been removed]
>

Re: CGS75 VCS Slew Rate Problem

2013-02-13 by cg_synth

> Thanks to Dean and Ken for helping me get my VCS issue resolved. Ken, that
>22pF cap was the culprit! Thanks for spotting that.
>
> I noticed that the Exp/Lin switches don't have an effect unless the CV
>pots are at something other than zero. Even with no external CV plugged in.
>That looks to be correct according to the schematic.

That is right. The pots now control how much the exp effect is applied, so
at zero, there is no effect.

Ken


_______________________________________________________________________
Ken Stone sasami@... otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: CGS75 VCS Slew Rate Problem

2013-02-13 by Richarius Molindarius

A little more careful attention is required for building the VCS, USG,
DUSG, Negative Slew, Positive Slew and Smooth Stepped Generator. They're
all quite specific. To me though, they (the USG and SSG) are a pair of the
most powerful analog modules, on the planet.
Transistor pinouts is a big attention requirement for all of them. To me,
that's the biggest attention requiring place.
Being careful - they all assemble fairly easily. :)
Show quoted textHide quoted text
On Tue, Feb 12, 2013 at 11:07 PM, <sasami@...> wrote:

> **
>
>
> > Thanks to Dean and Ken for helping me get my VCS issue resolved. Ken,
> that
> >22pF cap was the culprit! Thanks for spotting that.
> >
> > I noticed that the Exp/Lin switches don't have an effect unless the CV
> >pots are at something other than zero. Even with no external CV plugged
> in.
> >That looks to be correct according to the schematic.
>
> That is right. The pots now control how much the exp effect is applied, so
> at zero, there is no effect.
>
>
> Ken
>
> __________________________________________________________
> Ken Stone sasami@... otherunicorn@...
> Modular Synth PCBs for sale http://www.cgs.synth.net/>
> Australian Miniature Horses & Ponies http://www.blaze.net.au/~sasami/>
>
>
>



--
Take care,
Warmth and Peace,
Rich

http://www.damian.deathlehem.com/ - my modular synth
http://www.soundcloud.com/Richarius - my latest composition snippets
http://www.youtube.com/dolphinicus/ - various module videos of mine / etc.


[Non-text portions of this message have been removed]

Re: CGS75 VCS Slew Rate Problem

2013-02-13 by A S

Actually, I didn't populate the PCB. I bought it from someone that had
built it up to that point. I just added the mods and installed it behind a
front panel.

I agree that this is a very powerful module. I was up late last night
because of it! I'm amazed at how useful it is, wearing the many hats that
it does. :-)

Andrew

Show quoted textHide quoted text

On Wed, Feb 13, 2013 at 2:52 AM, Richarius Molindarius <
richmolindarius@...> wrote:

> A little more careful attention is required for building the VCS, USG,
> DUSG, Negative Slew, Positive Slew and Smooth Stepped Generator. They're
> all quite specific. To me though, they (the USG and SSG) are a pair of the
> most powerful analog modules, on the planet.
> Transistor pinouts is a big attention requirement for all of them. To me,
> that's the biggest attention requiring place.
> Being careful - they all assemble fairly easily. :)
>
>
> On Tue, Feb 12, 2013 at 11:07 PM, <sasami@...> wrote:
>
> > **
> >
> >
> > > Thanks to Dean and Ken for helping me get my VCS issue resolved. Ken,
> > that
> > >22pF cap was the culprit! Thanks for spotting that.
> > >
> > > I noticed that the Exp/Lin switches don't have an effect unless the CV
> > >pots are at something other than zero. Even with no external CV plugged
> > in.
> > >That looks to be correct according to the schematic.
> >
> > That is right. The pots now control how much the exp effect is applied,
> so
> > at zero, there is no effect.
> >
> >
> > Ken
> >
> > __________________________________________________________
> > Ken Stone sasami@... otherunicorn@...
> > Modular Synth PCBs for sale http://www.cgs.synth.net/>
> > Australian Miniature Horses & Ponies http://www.blaze.net.au/~sasami/>
> >
> >
> >
>
>
>
> --
> Take care,
> Warmth and Peace,
> Rich
>
> http://www.damian.deathlehem.com/ - my modular synth
> http://www.soundcloud.com/Richarius - my latest composition snippets
> http://www.youtube.com/dolphinicus/ - various module videos of mine / etc.
>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
>
> The CGS Modular Synth home page: http://www.cgs.synth.net/
> Yahoo! Groups Links
>
>
>
>


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