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CGS28 on 12v?

CGS28 on 12v?

2016-10-17 by shoskins99

Hi Everyone,


Hoping someone could give me so thoughts / ideas to try.


I have successfully built, tested and am running 3 x of the CGS28 board using 15v per Ken's page. They are in the COA Cannon Engine panel.


I have tested the entire design on 12v and it appears too function perfectly except for one notable item, the switch will not operate in reverse i.e. runs fine DOWN but when switched to UP it just sits there, on 15v this operation works perfectly.


Reason for change is most of the rest of my system is running 12v and this is the only panel seeming to require 15v.


I'm hoping perhaps a resistor change is the answer, any support / ideas would be truly welcome.


Thank you all.





Re: CGS28 on 12v?

2016-12-21 by soundbyarcone@gmail.com

I actually came here for the same reason. I am having the same issue with the CGS 28 modules on the Canon Engine.

I am running on 15V.

At first I was having issues with only one of the 3 CGS 28 modules working. I swapped the chips from the working module to the non-working ones and tracked it down to the TL074. I tried the circuit with numerous TL074's and only a few would work in the actual circuit properly. Some had issues with working up but not down and vice versa. I had no issue using the "bad" TL074's in completely different modules than the CGS 28.

I should also note that I also note that I am having the same issue with the UP and Down. I can not get any of the working modules to Reset when in UP mode.

I am also having issues with the CV output and Inverted where if more than one Sequential Switch is triggering on the same step at the same time there is a drop in the output CV.

Re: CGS28 on 12v?

2016-12-21 by cg_synth

If you are using 22R instead of beads on the power inputs, replace them with beads.

You will get a high voltage on the up/down input with nothing connected to it, and the up/down switch turned on. Do not be concerned, as this voltage is passing through 62k of resistance. Any output connected to this input will swamp that voltage.

The TL074 used as the input comparator is running between 0V and 15V. It is possible you have chips that do not have the output swing required. You say you tried different chips. Did you try different brands?
Reset issues may also be related to TL074 with poor output swing. That or you have diodes in backwards.

What is connected to the inputs? Just pots? When three sequential switches select the exact same source as their inputs, you have three times the load on what is driving them. The source will need to be buffered.

Re: CGS28 on 12v?

2016-12-21 by soundbyarcone@gmail.com

I am using beads on the power inputs.

As per your advice I ordered a different batch of TLO74's so I'm going to try that and see if that does the trick.

I am currently using the 100k resistor and 100 k pot without the switch and wired as per the schematic on the website. Would I need to reduce the value of the pots or the resistors since they are driving 3 Seq Switches at the same time?

Re: CGS28 on 12v?

2016-12-21 by cg_synth

You will get droop no matter what value resistors you use. Some buffering will be needed. You can use op-amps wired as voltage followers. For each stage/op-amp, connect the - input of the op-amp to the output of the op-amp. Connect the + input of the op-amp to the wiper of the pot. The output of the op-amp then goes to the three seq switches.

Re: CGS28 on 12v?

2016-12-21 by soundbyarcone@gmail.com

Sounds good. I'll perf board up a few buffers and let you know how it goes.

Re: CGS28 on 12v?

2016-12-21 by mount shasta

I've had success with substituting LM 324 for the TL074.
Also the STMicroeletronics TL074 seems to work better than the Texas Instruments version.

Re: CGS28 on 12v?

2016-12-21 by Ken Stone

LM324 is designed for single rail use, so that will help, but it is a slower chip, which in some circumstances, causes issues with CMOS counters. Neither 4017 or 4015 work with them. Your mileage may vary with other chip types.
Show quoted textHide quoted text
On Thu, Dec 22, 2016 at 1:54 AM, mount shasta tojpeters@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

I've had success with substituting LM 324 for the TL074.
Also the STMicroeletronics TL074 seems to work better than the Texas Instruments version.




--
Ken Stone otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>

Re: CGS28 on 12v?

2016-12-22 by soundbyarcone@gmail.com

Okay, I wired up some TL074's as a buffer.

I connected the +VCC pins on the TL074's to the +VE out on the Seq Switch PCB.
I connected the -VCC pin on the TL074's to ground. (Should this go to the -VE out on the Seq Switch board?)
I connected the pot wiper to the +IN on one of the opamps on the TL074.
I connected the -IN to the output.
I connected the output to the 3 Seq Switches.

I no longer get a voltage drop when it triggers on the same step on the 3 switches hooked up to the buffer however the range on the pot is very limited. With no buffer I have a range from 0V to 5V on the CV out but the step I have going through the buffer only has a range of about 0V to 1.5V.


Re: CGS28 on 12v?

2016-12-22 by Ken Stone

TL074 Pin 11 (-VCC) goes to -ve.
The voltage that you read on the wiper of the pot should be present on the output of the buffer also. If not, you may have some seriously weird TL074 chips - or a power supply issue.
Maybe add a resistor between the wiper and the +in for each buffer (merely as protection).
Show quoted textHide quoted text
On Thu, Dec 22, 2016 at 6:11 PM, soundbyarcone@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

Okay, I wired up some TL074's as a buffer.


I connected the +VCC pins on the TL074's to the +VE out on the Seq Switch PCB.
I connected the -VCC pin on the TL074's to ground. (Should this go to the -VE out on the Seq Switch board?)
I connected the pot wiper to the +IN on one of the opamps on the TL074.
I connected the -IN to the output.
I connected the output to the 3 Seq Switches.

I no longer get a voltage drop when it triggers on the same step on the 3 switches hooked up to the buffer however the range on the pot is very limited. With no buffer I have a range from 0V to 5V on the CV out but the step I have going through the buffer only has a range of about 0V to 1.5V.





--
Ken Stone otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>

Re: CGS28 on 12v?

2016-12-22 by soundbyarcone@gmail.com

Okay Awesome!

I swapped ground for VE- on the VCC- on the TL074 and the buffers work great.
Thanks again for your help on this!

I have some more TL074's on the way so I'll swap some of those out in the switches and let you know how it goes with not wanting to reset in the UP direction.

Re: CGS28 on 12v?

2016-12-27 by soundbyarcone@gmail.com

I got a shipment of different TLO74's and tried about 20 of them in the Sequential Switch circuit and none of them worked. Most of them I tried and couldn't even get the LED's to light up. I couple would light up the LED's but would not step or count when receiving clock. So far I have 2 out of about 40 TL074's that actually work in the circuit, but still no ability to reset when in the Up direction with any of them.

Re: CGS28 on 12v?

2016-12-27 by Ken Stone

It would seem you have a problem elsewhere. What voltages are the TL074 outputting in the high and low states? You aren't using 74xx4015 etc, are you?
Show quoted textHide quoted text
On Wed, Dec 28, 2016 at 5:26 AM, soundbyarcone@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

I got a shipment of different TLO74's and tried about 20 of them in the Sequential Switch circuit and none of them worked. Most of them I tried and couldn't even get the LED's to light up. I couple would light up the LED's but would not step or count when receiving clock. So far I have 2 out of about 40 TL074's that actually work in the circuit, but still no ability to reset when in the Up direction with any of them.




--
Ken Stone otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>

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