Cgs synth

--- In cgs_synth@yahoogroups.com, Stephen Richards <okayjustalittle@...> wrote:
>
> Hi Ken and all
>
> I'm building up the BOG panel and have done the two VCO's but am experiencing a few problems with both.
>
> One VCO is working fine apart from VC Freq pot ; seems to have zero effect on the Frequency when fed CV and when turned ; it also cuts out at the very lowest range , shorting to some sort of low droning sound.
>
> The Second VCO has no output , no change when Freq pot is moved but when FM'd , PWM'd or CV is applied the the Variable CV input , i'm getting sound from the outputs.
>
> When i checked this Second VCO , i found i had only soldered Pins 1 and 5 of the TL072 directly above the unicorn figure.
>
> Could this have caused damage to other parts of the circuit ?
>
>
> [Non-text portions of this message have been removed]
>

--- In cgs_synth@yahoogroups.com, Stephen Richards <okayjustalittle@...> wrote:
>
> Hi Ken and all
>
> I'm building up the BOG panel and have done the two VCO's but am experiencing a few problems with both.
>
> One VCO is working fine apart from VC Freq pot ; seems to have zero effect on the Frequency when fed CV and when turned ; it also cuts out at the very lowest range , shorting to some sort of low droning sound.
>
> The Second VCO has no output , no change when Freq pot is moved but when FM'd , PWM'd or CV is applied the the Variable CV input , i'm getting sound from the outputs.
>
> When i checked this Second VCO , i found i had only soldered Pins 1 and 5 of the TL072 directly above the unicorn figure.
>
> Could this have caused damage to other parts of the circuit ?
>
>
> [Non-text portions of this message have been removed]
>




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

>Hi Gary and all
>
>Just an update on the one i referred to as the 'Second VCO' that had no output.
>
>I changed out the TL072's , no change ; then the LM394 which i thought had

>
>Doing that i discovered that it's working , but only when the Tempco is

>
>I'm stumped.
>
>If it makes any difference , the VCO wiring diagram i followed was from

>
>http://www.diophantine.net/synth/bocgs/bocgs-wiring.html
>
>
>
>
>________________________________
> From: Mongo <zathrus1@...>
>To: cgs_synth@yahoogroups.com
>Sent: Sunday, November 4, 2012 2:44 AM
>Subject: [cgs_synth] Re: a couple of CGS48 VCO questions
>
>
>Â
>
>Regarding the first VCO, it sounds like you probably have a bad IC1, or a

>
>On the second one, it's possible that the VCO is actually running, but just

>
>Gary
>
>--- In cgs_synth@yahoogroups.com, Stephen Richards <okayjustalittle@...> wrote:
>>
>> Hi Ken and all
>>
>> I'm building up the BOG panel and have done the two VCO's but am

>>
>> One VCO is working fine apart from VC Freq pot ; seems to have

>>
>> The Second VCO has no output , no change when Freq pot is moved but when

>>
>> When i checked this Second VCO , i found i had only soldered Pins 1 and 5

>>
>> Could this have caused damage to other parts of the circuit ?
>>
>>
>> [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
>
>
>
>

>Hi Gary and all
>
>Just an update on the one i referred to as the 'Second VCO' that had no output.
>
>I changed out the TL072's , no change ; then the LM394 which i thought had

>
>Doing that i discovered that it's working , but only when the Tempco is

>
>I'm stumped.
>
>If it makes any difference , the VCO wiring diagram i followed was from

>
>http://www.diophantine.net/synth/bocgs/bocgs-wiring.html
>
>
>
>
>________________________________
> From: Mongo <zathrus1@...>
>To: cgs_synth@yahoogroups.com
>Sent: Sunday, November 4, 2012 2:44 AM
>Subject: [cgs_synth] Re: a couple of CGS48 VCO questions
>
>
>Â
>
>Regarding the first VCO, it sounds like you probably have a bad IC1, or a

>
>On the second one, it's possible that the VCO is actually running, but just

>
>Gary
>
>--- In cgs_synth@yahoogroups.com, Stephen Richards <okayjustalittle@...> wrote:
>>
>> Hi Ken and all
>>
>> I'm building up the BOG panel and have done the two VCO's but am

>>
>> One VCO is working fine apart from VC Freq pot ; seems to have

>>
>> The Second VCO has no output , no change when Freq pot is moved but when

>>
>> When i checked this Second VCO , i found i had only soldered Pins 1 and 5

>>
>> Could this have caused damage to other parts of the circuit ?
>>
>>
>> [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
>
>
>
>

On 4 Nov 2012, at 12:27, sasami@... wrote:

> >Does anyone know if I can sub a BAT42 for the BAT48 in the CGS 81 dual
> processor?
>
> Look at the datasheets:
> http://www.vishay.com/docs/85660/bat42,%20b.pdf
> http://www.datasheetcatalog.org/datasheet/vishay/85664.pdf
>
> 1)Reverse voltage 40 for the BAT48 vs 30. How much signal will it
> see? As it
> is back to back with another diode, it will only see the maximum of
> the
> other diode's forward drop, which is in the order of half a volt.
> Well, we
> ain't getting anywhere near 30 of 40 volts, so that won't make a
> differece.
>
> 2)Forward voltage drop. Both are around 400mV for 10mA through them.
> No
> difference there. The drop for the is greater at 50ma though. Will
> this matter?
>
> 3)Forward current. 350ma for the BAT48. Only 200 for the BAT42.
> Hmmm....
> Looking at the circuit we have 270k at one end connected to a summing
> node
> on an op-amp. Summing node is always zero volts. Other end of diodes
> goes to
> pots that can go between +/- 15. So maximum forward voltage across
> the 270k
> is 15 - diode drop, which we will ignore for the moment. Using ohms
> law
> V/R=I. 15 volts over 270000 ohms = 0.055555 micro amps. Okay, our
> current is
> so tiny we aren't going anywhere near the BAT42's 200mA limit, so
> that isn't
> a problem.
>
> Going back to 2) datasheet doesn't give forward voltage drop values
> for the
> current we are using, but we know it will probably be close enough
> between
> the two diode types. We have worked out that we won't damage the part
> because it is being used well within its specification. The only
> concern
> will be its behavior at these undocumented levels.
>
> Conclusion. Stick it in and try it. No harm will come of it. It will
> probably do the job.
>
> Reality: All these diodes are doing is providing a tiny dead band in
> the
> middle of the pot's rotation, so that zero is easier to select. Any
> variation in the diodes will only vary the width of this tiny gap. In
> all
> likelyhood, you won't be able to tell the difference.
>
> Hopefully next time you have a similar problem, you will have an idea
> of how
> to find out the answer yourself.
>
> Ken
>
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >[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/>
>
>
>

--- On Sun, 4/11/12, sasami@... <sasami@...> wrote:

From: sasami@... <sasami@...>
Subject: Re: [cgs_synth] BAT42 vs BAT48 in CGS 81
To: cgs_synth@yahoogroups.com
Date: Sunday, 4 November, 2012, 12:27


























>Does anyone know if I can sub a BAT42 for the BAT48 in the CGS 81 dual

processor?



Look at the datasheets:

http://www.vishay.com/docs/85660/bat42,%20b.pdf

http://www.datasheetcatalog.org/datasheet/vishay/85664.pdf



1)Reverse voltage 40 for the BAT48 vs 30. How much signal will it see? As it

is back to back with another diode, it will only see the maximum of the

other diode's forward drop, which is in the order of half a volt. Well, we

ain't getting anywhere near 30 of 40 volts, so that won't make a differece.



2)Forward voltage drop. Both are around 400mV for 10mA through them. No

difference there. The drop for the is greater at 50ma though. Will this matter?



3)Forward current. 350ma for the BAT48. Only 200 for the BAT42. Hmmm....

Looking at the circuit we have 270k at one end connected to a summing node

on an op-amp. Summing node is always zero volts. Other end of diodes goes to

pots that can go between +/- 15. So maximum forward voltage across the 270k

is 15 - diode drop, which we will ignore for the moment. Using ohms law

V/R=I. 15 volts over 270000 ohms = 0.055555 micro amps. Okay, our current is

so tiny we aren't going anywhere near the BAT42's 200mA limit, so that isn't

a problem.



Going back to 2) datasheet doesn't give forward voltage drop values for the

current we are using, but we know it will probably be close enough between

the two diode types. We have worked out that we won't damage the part

because it is being used well within its specification. The only concern

will be its behavior at these undocumented levels.



Conclusion. Stick it in and try it. No harm will come of it. It will

probably do the job.



Reality: All these diodes are doing is providing a tiny dead band in the

middle of the pot's rotation, so that zero is easier to select. Any

variation in the diodes will only vary the width of this tiny gap. In all

likelyhood, you won't be able to tell the difference.



Hopefully next time you have a similar problem, you will have an idea of how

to find out the answer yourself.



Ken



>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>[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]

>Hi Ken,
>
>Thank you for the detailed reply!
>
>I'd done a bit of maths, but was mainly looking at the datasheets and

>
>I posted the same Q on muff's, would you mind if I posted your answer in

>
>cheers
>
>charlie
>
>http://www.solinahifi.com/
>
>http://thebadproducer.tumblr.com/
>
>--- On Sun, 4/11/12, sasami@... <sasami@...> wrote:
>
>From: sasami@... <sasami@...>
>Subject: Re: [cgs_synth] BAT42 vs BAT48 in CGS 81
>To: cgs_synth@yahoogroups.com
>Date: Sunday, 4 November, 2012, 12:27
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>Â
>
>
>
>
>
>
>
>
>
> >Does anyone know if I can sub a BAT42 for the BAT48 in the CGS 81 dual
>
>processor?
>
>
>
>Look at the datasheets:
>
>http://www.vishay.com/docs/85660/bat42,%20b.pdf
>
>http://www.datasheetcatalog.org/datasheet/vishay/85664.pdf
>
>
>
>1)Reverse voltage 40 for the BAT48 vs 30. How much signal will it see? As it
>
>is back to back with another diode, it will only see the maximum of the
>
>other diode's forward drop, which is in the order of half a volt. Well, we
>
>ain't getting anywhere near 30 of 40 volts, so that won't make a differece.
>
>
>
>2)Forward voltage drop. Both are around 400mV for 10mA through them. No
>
>difference there. The drop for the is greater at 50ma though. Will this matter?
>
>
>
>3)Forward current. 350ma for the BAT48. Only 200 for the BAT42. Hmmm....
>
>Looking at the circuit we have 270k at one end connected to a summing node
>
>on an op-amp. Summing node is always zero volts. Other end of diodes goes to
>
>pots that can go between +/- 15. So maximum forward voltage across the 270k
>
>is 15 - diode drop, which we will ignore for the moment. Using ohms law
>
>V/R=I. 15 volts over 270000 ohms = 0.055555 micro amps. Okay, our current is
>
>so tiny we aren't going anywhere near the BAT42's 200mA limit, so that isn't
>
>a problem.
>
>
>
>Going back to 2) datasheet doesn't give forward voltage drop values for the
>
>current we are using, but we know it will probably be close enough between
>
>the two diode types. We have worked out that we won't damage the part
>
>because it is being used well within its specification. The only concern
>
>will be its behavior at these undocumented levels.
>
>
>
>Conclusion. Stick it in and try it. No harm will come of it. It will
>
>probably do the job.
>
>
>
>Reality: All these diodes are doing is providing a tiny dead band in the
>
>middle of the pot's rotation, so that zero is easier to select. Any
>
>variation in the diodes will only vary the width of this tiny gap. In all
>
>likelyhood, you won't be able to tell the difference.
>
>
>
>Hopefully next time you have a similar problem, you will have an idea of how
>
>to find out the answer yourself.
>
>
>
>Ken
>
>
>
>>
>
>>
>
>>
>
>>
>
>>
>
>>
>
>>
>
>>
>
>>
>
>>
>
>>
>
>>
>
>>
>
>>
>
>>
>
>>
>
>>
>
>>[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]
>
>
>
>------------------------------------
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>Yahoo! Groups Links
>
>
>
>

>Hi Gary and all
>
>Just an update on the one i referred to as the 'Second VCO' that had no output.
>
>I changed out the TL072's , no change ; then the LM394 which i thought had

>
>Doing that i discovered that it's working , but only when the Tempco is

>
>I'm stumped.
>
>If it makes any difference , the VCO wiring diagram i followed was from

>
>http://www.diophantine.net/synth/bocgs/bocgs-wiring.html
>
>
>
>
>________________________________
> From: Mongo <zathrus1@...>
>To: cgs_synth@yahoogroups.com
>Sent: Sunday, November 4, 2012 2:44 AM
>Subject: [cgs_synth] Re: a couple of CGS48 VCO questions
>
>
>Â
>
>Regarding the first VCO, it sounds like you probably have a bad IC1, or a

>
>On the second one, it's possible that the VCO is actually running, but just

>
>Gary
>
>--- In cgs_synth@yahoogroups.com, Stephen Richards <okayjustalittle@...> wrote:
>>
>> Hi Ken and all
>>
>> I'm building up the BOG panel and have done the two VCO's but am

>>
>> One VCO is working fine apart from VC Freq pot ; seems to have

>>
>> The Second VCO has no output , no change when Freq pot is moved but when

>>
>> When i checked this Second VCO , i found i had only soldered Pins 1 and 5

>>
>> Could this have caused damage to other parts of the circuit ?
>>
>>
>> [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
>
>
>
>

On 2012-11-06, at 7:29 PM, Stephen Richards <okayjustalittle@...> wrote:

> Hi Ken
>
> Just wanted to update what i said about the VCO ; if it makes any difference.
>
> With the Tempco disconnected On the GND rail side , the whole thing worked but the Fine Tune was functioning exactly the same as Frequency.
>
> The connections are : Fine Tune wiper to Tune , Freq to 1V/Oct as in the Diophantine Wiring diagrams.
>
> I have reconnected the Tempco and it's back to not working. In this state there is white noise and radio signals when i touch the knobs or panel.
>
> Also persistent Earth Hum.
>
> I have resoldered all of the board connections , there are no damaged pads ; all connection are correct.
>
> Tune : 0.3V
> 1V/Oct Freq : -14.87
> 1V Oct Input : -3.4
>
> This is the fourth one of these i've built , the one next to it is perfect. I'm stumped.
>
> ________________________________
> From: "sasami@..." <sasami@...>
> To: cgs_synth@yahoogroups.com
> Sent: Sunday, November 4, 2012 11:06 PM
> Subject: Re: [cgs_synth] Re: a couple of CGS48 VCO questions
>
>
>
> Usually, it is EXTREMELY unlikely that it is a damaged part. You probably
> have shorted two pads together/broken a pad by soldering for too long/used
> the wrong part somewhere. The tempco forms part of a voltage divider, so at
> a guess you have a wrong part (or other damage) around IC1 (TL072).
>
> First step: always check you have power on the pins of the IC.
> Second step: Make sure the "Trim zero" trim pot is near its center, not
> wound all the way up one end.
> Watch what happens at pin 7 of that TL072. It is the output of the input
> mixer stage.
> Possible help: You have two vcos. With them wired to exactly the same CVs
> (or using their tune pots set to the same positions) start comparing
> voltages between the two.
>
> >Hi Gary and all
> >
> >Just an update on the one i referred to as the 'Second VCO' that had no output.
> >
> >I changed out the TL072's , no change ; then the LM394 which i thought had
> blown.Â
> >
> >Doing that i discovered that it's working , but only when the Tempco is
> desoldered ( i desoldered the pad which is on the track that connects to Pin
> 7 of the LM394).
> >
> >I'm stumped.
> >
> >If it makes any difference , the VCO wiring diagram i followed was from
> this page from diophantine :
> >
> >http://www.diophantine.net/synth/bocgs/bocgs-wiring.html
> >
> >
> >
> >
> >________________________________
> > From: Mongo <zathrus1@...>
> >To: cgs_synth@yahoogroups.com
> >Sent: Sunday, November 4, 2012 2:44 AM
> >Subject: [cgs_synth] Re: a couple of CGS48 VCO questions
> >
> >
> >Â
> >
> >Regarding the first VCO, it sounds like you probably have a bad IC1, or a
> bad solder joint somewhere. Recheck your solder joints, and if everything
> looks ok, measure the voltage at pin 7 of IC1 - it should track when the
> incoming control voltage changes. If it doesn't, try replacing IC1.
> >
> >On the second one, it's possible that the VCO is actually running, but just
> at a very low frequency. I had that happen on a Teezer VCO once. I'd
> definitely suggest replacing the TL072 - you were running it without power,
> so who knows what happened inside that little fellow.
> >
> >Gary
> >
> >--- In cgs_synth@yahoogroups.com, Stephen Richards <okayjustalittle@...> wrote:
> >>
> >> Hi Ken and all
> >>
> >> I'm building up the BOG panel and have done the two VCO's but am
> experiencing a few problems with both.
> >>
> >> One VCO is working fine apart from VC Freq pot ; seems to have
> zero effect on the Frequency when fed CV and when turned ; it also cuts
> out at the very lowest range , shorting to some sort of low droning sound.
> >>
> >> The Second VCO has no output , no change when Freq pot is moved but when
> FM'd , PWM'd or CV is applied the the Variable CV input , i'm getting sound
> from the outputs.
> >>
> >> When i checked this Second VCO , i found i had only soldered Pins 1 and 5
> of the TL072 directly above the unicorn figure.
> >>
> >> Could this have caused damage to other parts of the circuit ?
> >>
> >>
> >> [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]
>
>


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

On 2012-11-06, at 7:29 PM, Stephen Richards <okayjustalittle@...> wrote:

> Hi Ken
>
> Just wanted to update what i said about the VCO ; if it makes any difference.
>
> With the Tempco disconnected On the GND rail side , the whole thing worked but the Fine Tune was functioning exactly the same as Frequency.
>
> The connections are : Fine Tune wiper to Tune , Freq to 1V/Oct as in the Diophantine Wiring diagrams.
>
> I have reconnected the Tempco and it's back to not working. In this state there is white noise and radio signals when i touch the knobs or panel.
>
> Also persistent Earth Hum.
>
> I have resoldered all of the board connections , there are no damaged pads ; all connection are correct.
>
> Tune : 0.3V
> 1V/Oct Freq : -14.87
> 1V Oct Input : -3.4
>
> This is the fourth one of these i've built , the one next to it is perfect. I'm stumped.
>
> ________________________________
> From: "sasami@..." <sasami@...>
> To: cgs_synth@yahoogroups.com
> Sent: Sunday, November 4, 2012 11:06 PM
> Subject: Re: [cgs_synth] Re: a couple of CGS48 VCO questions
>
>
>
> Usually, it is EXTREMELY unlikely that it is a damaged part. You probably
> have shorted two pads together/broken a pad by soldering for too long/used
> the wrong part somewhere. The tempco forms part of a voltage divider, so at
> a guess you have a wrong part (or other damage) around IC1 (TL072).
>
> First step: always check you have power on the pins of the IC.
> Second step: Make sure the "Trim zero" trim pot is near its center, not
> wound all the way up one end.
> Watch what happens at pin 7 of that TL072. It is the output of the input
> mixer stage.
> Possible help: You have two vcos. With them wired to exactly the same CVs
> (or using their tune pots set to the same positions) start comparing
> voltages between the two.
>
> >Hi Gary and all
> >
> >Just an update on the one i referred to as the 'Second VCO' that had no output.
> >
> >I changed out the TL072's , no change ; then the LM394 which i thought had
> blown.Â
> >
> >Doing that i discovered that it's working , but only when the Tempco is
> desoldered ( i desoldered the pad which is on the track that connects to Pin
> 7 of the LM394).
> >
> >I'm stumped.
> >
> >If it makes any difference , the VCO wiring diagram i followed was from
> this page from diophantine :
> >
> >http://www.diophantine.net/synth/bocgs/bocgs-wiring.html
> >
> >
> >
> >
> >________________________________
> > From: Mongo <zathrus1@...>
> >To: cgs_synth@yahoogroups.com
> >Sent: Sunday, November 4, 2012 2:44 AM
> >Subject: [cgs_synth] Re: a couple of CGS48 VCO questions
> >
> >
> >Â
> >
> >Regarding the first VCO, it sounds like you probably have a bad IC1, or a
> bad solder joint somewhere. Recheck your solder joints, and if everything
> looks ok, measure the voltage at pin 7 of IC1 - it should track when the
> incoming control voltage changes. If it doesn't, try replacing IC1.
> >
> >On the second one, it's possible that the VCO is actually running, but just
> at a very low frequency. I had that happen on a Teezer VCO once. I'd
> definitely suggest replacing the TL072 - you were running it without power,
> so who knows what happened inside that little fellow.
> >
> >Gary
> >
> >--- In cgs_synth@yahoogroups.com, Stephen Richards <okayjustalittle@...> wrote:
> >>
> >> Hi Ken and all
> >>
> >> I'm building up the BOG panel and have done the two VCO's but am
> experiencing a few problems with both.
> >>
> >> One VCO is working fine apart from VC Freq pot ; seems to have
> zero effect on the Frequency when fed CV and when turned ; it also cuts
> out at the very lowest range , shorting to some sort of low droning sound.
> >>
> >> The Second VCO has no output , no change when Freq pot is moved but when
> FM'd , PWM'd or CV is applied the the Variable CV input , i'm getting sound
> from the outputs.
> >>
> >> When i checked this Second VCO , i found i had only soldered Pins 1 and 5
> of the TL072 directly above the unicorn figure.
> >>
> >> Could this have caused damage to other parts of the circuit ?
> >>
> >>
> >> [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]
>
>

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




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

>Hi Ken
>
>Just wanted to update what i said about the VCO ; if it makes any difference.
>
>With the Tempco disconnected On the GND rail side , the whole thing worked

>
>The connections are : Fine Tune wiper to Tune , Freq to 1V/Oct as in the

>
>I have reconnected the Tempco and it's back to not working. In this state

>
>Also persistent Earth Hum.
>
>I have resoldered all of the board connections , there are no damaged pads

>
>Tune : 0.3V
>1V/Oct Freq : -14.87
>1V Oct Input : -3.4
>
>This is the fourth one of these i've built , the one next to it is perfect.

>
>
>
>________________________________
> From: "sasami@..." <sasami@...>
>To: cgs_synth@yahoogroups.com
>Sent: Sunday, November 4, 2012 11:06 PM
>Subject: Re: [cgs_synth] Re: a couple of CGS48 VCO questions
>
>
>Â
>Usually, it is EXTREMELY unlikely that it is a damaged part. You probably
>have shorted two pads together/broken a pad by soldering for too long/used
>the wrong part somewhere. The tempco forms part of a voltage divider, so at
>a guess you have a wrong part (or other damage) around IC1 (TL072).
>
>First step: always check you have power on the pins of the IC.
>Second step: Make sure the "Trim zero" trim pot is near its center, not
>wound all the way up one end.
>Watch what happens at pin 7 of that TL072. It is the output of the input
>mixer stage.
>Possible help: You have two vcos. With them wired to exactly the same CVs
>(or using their tune pots set to the same positions) start comparing
>voltages between the two.
>
>
>>Hi Gary and all
>>
>>Just an update on the one i referred to as the 'Second VCO' that had no

>>
>>I changed out the TL072's , no change ; then the LM394 which i thought had
>blown.ÂÂ
>>
>>Doing that i discovered that it's working , but only when the Tempco is
>desoldered ( i desoldered the pad which is on the track that connects to Pin
>7 of the LM394).
>>
>>I'm stumped.
>>
>>If it makes any difference , the VCO wiring diagram i followed was from
>this page from diophantine :
>>
>>http://www.diophantine.net/synth/bocgs/bocgs-wiring.html
>>
>>
>>
>>
>>________________________________
>> From: Mongo <zathrus1@...>
>>To: cgs_synth@yahoogroups.com
>>Sent: Sunday, November 4, 2012 2:44 AM
>>Subject: [cgs_synth] Re: a couple of CGS48 VCO questions
>>
>>
>>ÂÂ
>>
>>Regarding the first VCO, it sounds like you probably have a bad IC1, or a
>bad solder joint somewhere. Recheck your solder joints, and if everything
>looks ok, measure the voltage at pin 7 of IC1 - it should track when the
>incoming control voltage changes. If it doesn't, try replacing IC1.
>>
>>On the second one, it's possible that the VCO is actually running, but just
>at a very low frequency. I had that happen on a Teezer VCO once. I'd
>definitely suggest replacing the TL072 - you were running it without power,
>so who knows what happened inside that little fellow.
>>
>>Gary
>>
>>--- In cgs_synth@yahoogroups.com, Stephen Richards <okayjustalittle@...>

>>>
>>> Hi Ken and all
>>>
>>> I'm building up the BOG panel and have done the two VCO's but am
>experiencing a few problems with both.
>>>
>>> One VCO is working fine apart from VC Freq pot ; seems to have
>zero effect on the Frequency when fed CV and when turned ; it also cuts
>out at the very lowest range , shorting to some sort of low droning sound.
>>>
>>> The Second VCO has no output , no change when Freq pot is moved but when
>FM'd , PWM'd or CV is applied the the Variable CV input , i'm getting sound
>from the outputs.
>>>
>>> When i checked this Second VCO , i found i had only soldered Pins 1 and 5
>of the TL072 directly above the unicorn figure.
>>>
>>> Could this have caused damage to other parts of the circuit ?
>>>
>>>
>>> [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]
>
>
>
>------------------------------------
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>Yahoo! Groups Links
>
>
>
>

>Hi Ken
>
>Just wanted to update what i said about the VCO ; if it makes any difference.
>
>With the Tempco disconnected On the GND rail side , the whole thing worked

>
>The connections are : Fine Tune wiper to Tune , Freq to 1V/Oct as in the

>
>I have reconnected the Tempco and it's back to not working. In this state

>
>Also persistent Earth Hum.
>
>I have resoldered all of the board connections , there are no damaged pads

>
>Tune : 0.3V
>1V/Oct Freq : -14.87
>1V Oct Input : -3.4
>
>This is the fourth one of these i've built , the one next to it is perfect.

>
>
>
>________________________________
> From: "sasami@..." <sasami@...>
>To: cgs_synth@yahoogroups.com
>Sent: Sunday, November 4, 2012 11:06 PM
>Subject: Re: [cgs_synth] Re: a couple of CGS48 VCO questions
>
>
>Â
>Usually, it is EXTREMELY unlikely that it is a damaged part. You probably
>have shorted two pads together/broken a pad by soldering for too long/used
>the wrong part somewhere. The tempco forms part of a voltage divider, so at
>a guess you have a wrong part (or other damage) around IC1 (TL072).
>
>First step: always check you have power on the pins of the IC.
>Second step: Make sure the "Trim zero" trim pot is near its center, not
>wound all the way up one end.
>Watch what happens at pin 7 of that TL072. It is the output of the input
>mixer stage.
>Possible help: You have two vcos. With them wired to exactly the same CVs
>(or using their tune pots set to the same positions) start comparing
>voltages between the two.
>
>
>>Hi Gary and all
>>
>>Just an update on the one i referred to as the 'Second VCO' that had no

>>
>>I changed out the TL072's , no change ; then the LM394 which i thought had
>blown.ÂÂ
>>
>>Doing that i discovered that it's working , but only when the Tempco is
>desoldered ( i desoldered the pad which is on the track that connects to Pin
>7 of the LM394).
>>
>>I'm stumped.
>>
>>If it makes any difference , the VCO wiring diagram i followed was from
>this page from diophantine :
>>
>>http://www.diophantine.net/synth/bocgs/bocgs-wiring.html
>>
>>
>>
>>
>>________________________________
>> From: Mongo <zathrus1@...>
>>To: cgs_synth@yahoogroups.com
>>Sent: Sunday, November 4, 2012 2:44 AM
>>Subject: [cgs_synth] Re: a couple of CGS48 VCO questions
>>
>>
>>ÂÂ
>>
>>Regarding the first VCO, it sounds like you probably have a bad IC1, or a
>bad solder joint somewhere. Recheck your solder joints, and if everything
>looks ok, measure the voltage at pin 7 of IC1 - it should track when the
>incoming control voltage changes. If it doesn't, try replacing IC1.
>>
>>On the second one, it's possible that the VCO is actually running, but just
>at a very low frequency. I had that happen on a Teezer VCO once. I'd
>definitely suggest replacing the TL072 - you were running it without power,
>so who knows what happened inside that little fellow.
>>
>>Gary
>>
>>--- In cgs_synth@yahoogroups.com, Stephen Richards <okayjustalittle@...>

>>>
>>> Hi Ken and all
>>>
>>> I'm building up the BOG panel and have done the two VCO's but am
>experiencing a few problems with both.
>>>
>>> One VCO is working fine apart from VC Freq pot ; seems to have
>zero effect on the Frequency when fed CV and when turned ; it also cuts
>out at the very lowest range , shorting to some sort of low droning sound.
>>>
>>> The Second VCO has no output , no change when Freq pot is moved but when
>FM'd , PWM'd or CV is applied the the Variable CV input , i'm getting sound
>from the outputs.
>>>
>>> When i checked this Second VCO , i found i had only soldered Pins 1 and 5
>of the TL072 directly above the unicorn figure.
>>>
>>> Could this have caused damage to other parts of the circuit ?
>>>
>>>
>>> [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]
>
>
>
>------------------------------------
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>Yahoo! Groups Links
>
>
>
>

>Hi Ken
>
>Just wanted to update what i said about the VCO ; if it makes any difference.
>
>With the Tempco disconnected On the GND rail side , the whole thing worked

>
>The connections are : Fine Tune wiper to Tune , Freq to 1V/Oct as in the

>
>I have reconnected the Tempco and it's back to not working. In this state

>
>Also persistent Earth Hum.
>
>I have resoldered all of the board connections , there are no damaged pads

>
>Tune : 0.3V
>1V/Oct Freq : -14.87
>1V Oct Input : -3.4
>
>This is the fourth one of these i've built , the one next to it is perfect.

>
>
>
>________________________________
> From: "sasami@..." <sasami@...>
>To: cgs_synth@yahoogroups.com
>Sent: Sunday, November 4, 2012 11:06 PM
>Subject: Re: [cgs_synth] Re: a couple of CGS48 VCO questions
>
>
>Â
>Usually, it is EXTREMELY unlikely that it is a damaged part. You probably
>have shorted two pads together/broken a pad by soldering for too long/used
>the wrong part somewhere. The tempco forms part of a voltage divider, so at
>a guess you have a wrong part (or other damage) around IC1 (TL072).
>
>First step: always check you have power on the pins of the IC.
>Second step: Make sure the "Trim zero" trim pot is near its center, not
>wound all the way up one end.
>Watch what happens at pin 7 of that TL072. It is the output of the input
>mixer stage.
>Possible help: You have two vcos. With them wired to exactly the same CVs
>(or using their tune pots set to the same positions) start comparing
>voltages between the two.
>
>
>>Hi Gary and all
>>
>>Just an update on the one i referred to as the 'Second VCO' that had no

>>
>>I changed out the TL072's , no change ; then the LM394 which i thought had
>blown.ÂÂ
>>
>>Doing that i discovered that it's working , but only when the Tempco is
>desoldered ( i desoldered the pad which is on the track that connects to Pin
>7 of the LM394).
>>
>>I'm stumped.
>>
>>If it makes any difference , the VCO wiring diagram i followed was from
>this page from diophantine :
>>
>>http://www.diophantine.net/synth/bocgs/bocgs-wiring.html
>>
>>
>>
>>
>>________________________________
>> From: Mongo <zathrus1@...>
>>To: cgs_synth@yahoogroups.com
>>Sent: Sunday, November 4, 2012 2:44 AM
>>Subject: [cgs_synth] Re: a couple of CGS48 VCO questions
>>
>>
>>ÂÂ
>>
>>Regarding the first VCO, it sounds like you probably have a bad IC1, or a
>bad solder joint somewhere. Recheck your solder joints, and if everything
>looks ok, measure the voltage at pin 7 of IC1 - it should track when the
>incoming control voltage changes. If it doesn't, try replacing IC1.
>>
>>On the second one, it's possible that the VCO is actually running, but just
>at a very low frequency. I had that happen on a Teezer VCO once. I'd
>definitely suggest replacing the TL072 - you were running it without power,
>so who knows what happened inside that little fellow.
>>
>>Gary
>>
>>--- In cgs_synth@yahoogroups.com, Stephen Richards <okayjustalittle@...>

>>>
>>> Hi Ken and all
>>>
>>> I'm building up the BOG panel and have done the two VCO's but am
>experiencing a few problems with both.
>>>
>>> One VCO is working fine apart from VC Freq pot ; seems to have
>zero effect on the Frequency when fed CV and when turned ; it also cuts
>out at the very lowest range , shorting to some sort of low droning sound.
>>>
>>> The Second VCO has no output , no change when Freq pot is moved but when
>FM'd , PWM'd or CV is applied the the Variable CV input , i'm getting sound
>from the outputs.
>>>
>>> When i checked this Second VCO , i found i had only soldered Pins 1 and 5
>of the TL072 directly above the unicorn figure.
>>>
>>> Could this have caused damage to other parts of the circuit ?
>>>
>>>
>>> [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]
>
>
>
>------------------------------------
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>Yahoo! Groups Links
>
>
>
>