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Tuning..again - Transposition gate zeroing?

 

So I am chasing the dragon yet again...

What I am after is this steady ultraslow sweep between the channels and some of them are banging to quickly.

I have never adjusted transposition gate zeroing before and here is my question (I?d like to know do I read the manual right..).?

1. What does really the transposition gate zeroing do? Can it effect tuning between two channels on one voice?

2. ?It says I should measure the voltage between CP6 and EK terminals. Does that mean I should put a minus probe on CP6 and plus on EK ?(or vice-versa)?

3. It says I should read .120mV. at 2?. My DVM is very basic and the max resolution I get is 200m. Depending on the board i read 0.28 to 0.40! I have no clue is that normal every board is way off?


Thanks in advance for your patient answers.
 

Hi,


1. What does really the transposition gate zeroing do?

It does precisely what its name says: it insures the voltage used? to determine the frequency of the VCO is zero, or reasonably close to zero.


?? Can it effect tuning between two channels on one voice?

If you modify VR1 without modifying anything else, yes. But tuning the M-board requires several settings which should all be done. (As explained on page 5 of the CS-80 adjustment procedure)


2. ?It says I should measure the voltage between CP6 and EK terminals. Does that mean I should put a minus probe on CP6 and plus on EK ?(or vice-versa)?

It does not matter. Since the measure will vary around 0, you should expect negative as well as positive values, depending on the setting of each variable resistor. With a DVM this should not be a problem.


3. It says I should read .120mV. at 2?.

Not exactly: it says you should set the voltage to 0, plus or minus at most 0.120 mv. The closest to 0 the better.


My DVM is very basic and the max resolution I get is 200m. Depending on the board i read 0.28 to 0.40! I have no clue is that normal every board is way off?

The idea is to set VR1 so that you measure a voltage between CP6 and EK as close to 0 as possible.

But remember that the tuning of a board is a process that requires all steps 7 to 12 to be performed.


Joachim
 

Thank you Joachim for the complete and patient answer! You?re always there for us.
I am aware of all the steps but I never did the 7 (transposition gate zeroing). It seems that all my M boards are off (none of them are close to zero).

My PSU is calibrated and solid, but I have problems getting accurate voltages on the KAS board (page 3)..
step 1 -ok 4,00V
step 2 - 125,7mV instead 125,0mV potentiometer to the max
step 3 - ?125,1mV instead 125,1mV
step 4 - 131,4mV instead 132,4mV potentiometer to the max
Increasing the voltage on TU to around 4,04V helps for step 4 but the others go south.
step 5 and 6 ok.
 

step 1 - ok 4,00V
This is the expected voltage for C6.

step 2 - 125,7mV instead 125,0mV potentiometer to the max
This means that when you play C1, the pitch will be too high (roughly by 10 cents).
The manual says you should not go above 0.1 %, that is 125,12 mV (corresponding roughly to 1.4 cents).

If this variable resistor is damaged, you should perhaps consider changing it.
You could first check it: once unsoldered, its total resistance should be 20 ohms.

step 3 - 125,1mV instead 125,1mV
If you meant 125,1 mV instead of 125,0 mV, that's within the tolerances.

step 4 - 131,4mV instead 132,4mV potentiometer to the max
This is 15 cents too low.

Increasing the voltage on TU to around 4,04V helps for step 4 but the others go south.
That's obviously not the way to go ;-) Keep TU to 4 V.

Anyway, fix the issues in the order of the steps.
 

Thanks Joachim.
I have managed to make the adjustments on the KAS a little better (still few cents out tough..)
Now I have finished the complete tuning procedure and it seems to be pretty neat.
I have found out that after completing the step 8 it is important do repeat the 7 and 8 again until it?s within the specs.
After finishing the procedure a strange problem manifested itself...the board 4 channel 1 is mute ?at the panel, memory 1,2 and funky 3 buttons (it is like there is no trigger). Other presets work fine on it but it seems to be louder that the others..
 

The issue you're describing is rather strange. It only impacts master board I-4. But what is really weird is that it only happens when one of the last four preset selectors is pressed.
The trigger wire is certainly not the problem since the other presets work with this board.
Did you try modifying the panel settings while playing board I-4, just to see if it's bound to a specific parameter of the synthesis line ? The first idea that comes to mind is that you inadvertently modified an other variable resistor while applying the tuning procedure. You could also make a thorough comparison with board I-3 for instance.
 

Well, it got even better.
I?ve tried to fond a possible short and the only board except of M boards I have removed was the BA board (4.0V adjustment). I've inspected it and it seemed fine. After I put it back in and power up the synth it played a low note and died. There was a smell of something burned so I?ve turned it off immediately.
Now the PSU is dead. No power. All the fuses intact..
I will recap it and see if it will help but I am pretty mad cause I took extra care while handling this synth and even the fuses did not save the day.?
Visually nothing is wrong with the PSU. No leaking or signs of burned components. The only thing that smells is the micron 78 resistor on the heat sink. I will try to change that too.
Honestly...lot of fun :(
 

A little update:
1. Recapped the PSU. - still bad - showing 7,4V instead of 15V for example.
2. Changed the two 1ohm ceramic resistors - helped ! I could calibrate the PSU now.
3. Calibrated PSU - reinstalled.
4. Should I try it out? Yes. I`have tried.
5. Turned the synth on - lights did not come up, same low single note played. Turned it off quickly..
6. PSU is bad again (showing 0,2V on 15,0 terminal)....resistors seem not burned this time, caps seem intact.
7. Back to square one....I have no idea what is causing this...
 

Changing 4558 IC on the PSU cured it again...All the voltages are back - phew!

I won?t turn it again until I find out what is killing my PSU. Could it be the BA board?
 

Hello Pyjamagroove,

I see you are trying to calibrate your CS80. A year ago I did a complete calibration of my CS80 from scratch and I am happy that I didn't commit suicide during it, also Joachim and a good friend have been a big help through my journey too. I also killed some parts here and there, unfortunately also a custom chip, but I was able to sacrifice one from the chorus which I don't use. I see that you are puzzled here and there, so was I for days. :)

I documented the whole challenge and findings and workarounds in a blog (so if I have to ever do it again I know where to get my own information that I already forgot :)). I also updated the calibration documentation.

Maybe it's some help here and there to you when you stumble over all the wonderings. Check it out:




kind regards,
Michael



---In yamahacs80@..., <pyjamagroove@...> wrote :

Thanks Joachim.
I have managed to make the adjustments on the KAS a little better (still few cents out tough..)
Now I have finished the complete tuning procedure and it seems to be pretty neat.
I have found out that after completing the step 8 it is important do repeat the 7 and 8 again until it?s within the specs.
After finishing the procedure a strange problem manifested itself...the board 4 channel 1 is mute ?at the panel, memory 1,2 and funky 3 buttons (it is like there is no trigger). Other presets work fine on it but it seems to be louder that the others..
 

Hi Michael,
Thank you very much for contacting me. I know your blog very well - it has been a great guide and a source of very valuable information to me. I have learned a lot reading it preventing me to make several mistakes.
What has happened to my synth is very unfortunate and I am also very frustrated. Right now I have upper and lower rails shorted and I am trying ro find a cause. I have created a separate thread to address this issue.
Thanks again.

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