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CGS89 Gate Seq: no signal at FULL & PULSE outputs [SOLVE
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author CGS89 Gate Seq: no signal at FULL & PULSE outputs [SOLVE
batchas
As I have no signal at FM1, Po1, FM2, Po2 (the main FULL OUT / PULSE OUT on my panel for channel 1 and channel 2) I started troubleshoot, step by step.


Then arrived at CD4081…
Each step I set with switches for ch1 or ch2 works, I see them at CD4081. Means setting GATE or TRIG via switch works.
But nothing at outputs pin 10 or 4, nor 3 or 11 zombie

CD4081

Pin 1 clock
Pin 2 the steps that are switched on as FULL on ch2
Pin 3 nothing (0V)
Pin 4 nothing (0V)
Pin 5 clock
Pin 6 the steps that are switched on as PULSE on ch2
Pin 7 GND (0V)
Pin 2 the steps that are switched on as PULSE on ch1
Pin 9 clock
Pin 10 nothing (0V)
Pin 11 nothing (0V)
Pin 12 the steps that are switched on as FULL on ch1
Pin 13 clock
Pin 14 +12v



I changed the CD4081 for other brand, same.
I built 2 x CGS89, same issue :(

EDIT: changing title. SOLVED.
Hakan01
In your schematic, what is C connected too?
It should be connected to a postive voltage
cygmu
What is happening at point H? I guess this is the hold signal -- is it somewhere near the negative rail?

If so then one thing that can make this circuit misbehave is the fact that a TL074 does not like to see inputs near to the negative power supply. Things go very weird when this happens -- I had this experience with a CGS28 which has a very similar bit of circuitry. It resolved as soon as I changed the TL074 to an LM324.

Probably not the problem in this case but worth a try!

[edit: I located the power arrangements for the various ICs on the schematic and now I see that H should be near 0V so almost certainly this is not the issue. Oh well. Sorry.]
tojpeters
Do you have a 15v supply you can try this on
batchas
Hakan01 wrote:
In your schematic, what is C connected too?
It should be connected to a postive voltage

I should have add the link to Ken's page, where the schematic is, sorry:
https://www.cgs.synth.net/modules/cgs89_gate_sequencer.html
batchas
cygmu wrote:
[edit: I located the power arrangements for the various ICs on the schematic and now I see that H should be near 0V so almost certainly this is not the issue. Oh well. Sorry.]

thumbs up
batchas
tojpeters wrote:
Do you have a 15v supply you can try this on

Thanx. I am going to try with 15v supply and let you know.

I thought I'd try with +15v anyway cause without LED the individual gate outs show +4.2v and with LEDs installed +2v, way too low to loop, gate, retrig or whatever. I guess I'll need anyway to lower the RLED resistor values against this voltage drop (I'm gonna test with adding resistor in parallel to the 1k installed at RLED).
batchas
tojpeters wrote:
Do you have a 15v supply you can try this on

So I just checked with 15v supply. Same behaviour.
FM1, Po1, FM2, Po2 (no main FULL OUT / PULSE OUT).
CD4081 ame as in op.


Also same low voltage at the GATE outs as with 12v power supply.
batchas
The measurements on the TL074 look like this. Same on both CGS89, with or without the part with switch FULL OUT / PULSE outputs.

Pin 1 -10,4v
Pin 2 +2v
Pin 3 clock (0.4v peak-to-peak)
Pin 4 +9v
Pin 5 0v
Pin 6 +2v
Pin 7 -10.4v

Pin 8 -10.4v
Pin 9 +2v
Pin 10 0v
Pin 11 -12v
Pin 12 clock (0.4v peak-to-peak)
Pin 13 +2v
Pin 14 -10.4v

Changed TL074, same behaviour.
Looks kindof weird, isn't it?
batchas
Hmmm.
Wondering if leaving the RY empty was the cleverst thing to do!
I thought it was only if adding a OR gate option, but I'm gonna check the schematic again. Maybe it's because I left them empty and should have added 1K res instead.
batchas
batchas wrote:
Hmmm.
Wondering if leaving the RY empty was the cleverst thing to do!
I thought it was only if adding a OR gate option, but I'm gonna check the schematic again. Maybe it's because I left them empty and should have added 1K res instead.

d'oh! d'oh! d'oh!

Tsss... RY should not be left empty.

Now all is working fine w00t

Voltages at outputs also alright now.

I will show what I did once all is mounted cause I'm quite proud of it. But first I'll make sure everything is really working haha.
cygmu
I am surprised you got much output at all without those resistors. Glad you found it!
batchas
cygmu wrote:
I am surprised you got much output at all without those resistors.

Indeed. Might be the reason why I didn't think first of this missing RY pair.


Now all functions well with the PCB I made for the project.


Link: https://www.youtube.com/watch?v=CBcQSd6TRN0



But then a layout error came to light once I mounted all on the panel.
First it was an error IMO to name the 2 different outs TRIG and GATE (cause what I named GATE looks actually like a mix of trig & gate. I'll check tomorrow more precisely).

But most important I made the layout so the sequence goes up from 1 to 5 then down from 6 to 10 (following a rectangle so to say).
And obv. this is not what I did on the PCB I made, so now the order is not consistent.
Not dramatic, but a bit frustrating.

In red is the order of steps on the PCB:
batchas
batchas wrote:
First it was an error IMO to name the 2 different outs TRIG and GATE (cause what I named GATE looks actually like a mix of trig & gate. I'll check tomorrow more precisely).

Okay. I know now. I should have named the GATE OUT like MIX OUT instead.

EDIT: I named it GATEMIX.
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