Yamaha CS80

Hi All,

I acquired my CS80 (unit 1670) less than a month ago. It has a couple of
known issues all bound to the keys.
The one that could be fixed:
- a sequence of 6 consecutive keys had neither AT nor IT. The faulty
chip was a 4016 (Gates) on the TKC.
- two keys had no IT but AT was OK. It took me some time to find out
that this was due to the PCB holding the "IT/note" metal strips at the
back end of the keys. I had to solder two short wires to bypass the two
non conductive printed tracks, although nothing could be seen (no
scratch on the PCB). Has someone already had this problem ?

I'm stuck with the last issue (at least known to me for the moment).
One AT sensor board seems faulty under one key (G#3).
Here is a close-up of the faulty AT sensor board
<http://groups.yahoo.com/group/yamahacs80/photos/album/1863574374/pic/56\
3904716/view>
Compares to the other tracks on the same board, nothing seems to be
different.
The problem is that the voltages at T3 are always two high:
The voltages for a normal key vary (as I measure them) from -0.3V (not
pressed) to 6.2V (pressed to the maximum)
Under the faulty key, the values are 1,7V (not pressed) to 8.4V
(pressed to the maximum).
So the voltages seem to be shifted upward by 2 V under the faulty key.
Certainly some printed resistor is faulty.
The result is that, depending on the AT settings for the current preset,
the corresponding note sounds a bit too loud and can even be heard when
it should not.
I switched the PCB with the last one on the right, so the problem is now
on G#5, where it is slightly less audible, but still there (no miracle
!).
Is there a way to somehow repair this issue ? If not, has someone one
such board (one for the black keys) in his spares stock and would accept
selling it ?
Any help will be appreciated.

Thanks,
Joachim




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

Hi Joachim

Sounds like there's some voltage leaking into areas you don't want it.
First thing I'd try is giving the board a good clean with some isopropyl
alcohol.
Could be that at some point something has been spilled onto the board
and it's gone conductive.

Give it a really good clean using a cotton bud, and then try it again.
you may find it does the trick, or you may find that it reduces the
problem. If it reduces it, then you're on the right track and it needs
more cleaning.
If it makes no difference then it's back to the drawing board :-s

Hope that helps.

Bob

On 19/05/2013 10:23, joachim.milson wrote:
>
> Hi All,
>
> I acquired my CS80 (unit 1670) less than a month ago. It has a couple of
> known issues all bound to the keys.
> The one that could be fixed:
> - a sequence of 6 consecutive keys had neither AT nor IT. The faulty
> chip was a 4016 (Gates) on the TKC.
> - two keys had no IT but AT was OK. It took me some time to find out
> that this was due to the PCB holding the "IT/note" metal strips at the
> back end of the keys. I had to solder two short wires to bypass the two
> non conductive printed tracks, although nothing could be seen (no
> scratch on the PCB). Has someone already had this problem ?
>
> I'm stuck with the last issue (at least known to me for the moment).
> One AT sensor board seems faulty under one key (G#3).
> Here is a close-up of the faulty AT sensor board
> <http://groups.yahoo.com/group/yamahacs80/photos/album/1863574374/pic/56\
> 3904716/view
> <http://groups.yahoo.com/group/yamahacs80/photos/album/1863574374/pic/563904716/view>>
> Compares to the other tracks on the same board, nothing seems to be
> different.
> The problem is that the voltages at T3 are always two high:
> The voltages for a normal key vary (as I measure them) from -0.3V (not
> pressed) to 6.2V (pressed to the maximum)
> Under the faulty key, the values are 1,7V (not pressed) to 8.4V
> (pressed to the maximum).
> So the voltages seem to be shifted upward by 2 V under the faulty key.
> Certainly some printed resistor is faulty.
> The result is that, depending on the AT settings for the current preset,
> the corresponding note sounds a bit too loud and can even be heard when
> it should not.
> I switched the PCB with the last one on the right, so the problem is now
> on G#5, where it is slightly less audible, but still there (no miracle
> !).
> Is there a way to somehow repair this issue ? If not, has someone one
> such board (one for the black keys) in his spares stock and would accept
> selling it ?
> Any help will be appreciated.
>
> Thanks,
> Joachim
>
> [Non-text portions of this message have been removed]
>
>



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

Thanks Bob for your answer.

I already cleaned the boards and sensors carefully.
The contacts are very clean. I did it very carefully under a magnifying lens. Also, I changed the sensor with an other one but the issue is still there. So on my opinion, the problem is the PCB itself.

Joachim

Hmmm Odd.

The other thing that I'd be inclined to check is that any through hole
connections on the board are all in tact.
Occasionally I've come across PTH where the plating has become damaged
and the two sides of the board are no longer connected.
This can result in floating connections that can manifest as spurious DC
voltages where they shouldn't be any.

On 19/05/2013 11:31, joachim.milson wrote:
>
>
>
> Thanks Bob for your answer.
>
> I already cleaned the boards and sensors carefully.
> The contacts are very clean. I did it very carefully under a
> magnifying lens. Also, I changed the sensor with an other one but the
> issue is still there. So on my opinion, the problem is the PCB itself.
>
> Joachim
>
>



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

OK. Just been looking at the pic, and the service manual.
It could well be that the resistive print in that area is faulty either
due to wear and tear, or just plain old age.
Looking at the service manual it suggests that on either side of the
contact resistor (topologically speaking) are some resistors. If you're
feeling brave you try adding a new resistor into the path to compensate
for the error?

B

On 19/05/2013 11:31, joachim.milson wrote:
>
>
>
> Thanks Bob for your answer.
>
> I already cleaned the boards and sensors carefully.
> The contacts are very clean. I did it very carefully under a
> magnifying lens. Also, I changed the sensor with an other one but the
> issue is still there. So on my opinion, the problem is the PCB itself.
>
> Joachim
>
>



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

>Occasionally I've come across PTH where the plating has become damaged

and the two sides of the board are no longer connected.
This PCB is printed on one side only. Its lower side is in direct
contact with the metal plate on which it is screwed.

> It could well be that the resistive print in that area is faulty

either due to wear and tear, or just plain old age.
That's what I fear. I'm surprised however that only this part of this
board is concerned.

> Looking at the service manual it suggests that on either side of the

contact resistor (topologically speaking) are some resistors.
The overall circuit diagram seems wrong. Look here for what could be a
more faithful diagram AT-sensor resistors
<http://groups.yahoo.com/group/yamahacs80/photos/album/1863574374/pic/12\
73145453/view>

> If you're feeling brave you try adding a new resistor into the path to

compensate for the error?
I'll probably try that between T3 and -15.

Thanks,

Joachim




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

Hi Joachim

Yes the reality is slightly different, but it's effectively the same thing.
A resistor to compensate is probably the way forward.

I'm just getting to grips with the larger Yamaha CS series recently.
I've done a lot of different synths over the years, but never got my
hands dirty on a CS50/60/80 until recently. Now I seem to have them
coming at me from all sides.

Let me know if the resistor addition sorts out the issue.

Bob

On 19/05/2013 16:29, joachim.milson wrote:
>
> >Occasionally I've come across PTH where the plating has become damaged
> and the two sides of the board are no longer connected.
> This PCB is printed on one side only. Its lower side is in direct
> contact with the metal plate on which it is screwed.
>
> > It could well be that the resistive print in that area is faulty
> either due to wear and tear, or just plain old age.
> That's what I fear. I'm surprised however that only this part of this
> board is concerned.
>
> > Looking at the service manual it suggests that on either side of the
> contact resistor (topologically speaking) are some resistors.
> The overall circuit diagram seems wrong. Look here for what could be a
> more faithful diagram AT-sensor resistors
> <http://groups.yahoo.com/group/yamahacs80/photos/album/1863574374/pic/12\
> 73145453/view
> <http://groups.yahoo.com/group/yamahacs80/photos/album/1863574374/pic/1273145453/view>>
>
> > If you're feeling brave you try adding a new resistor into the path to
> compensate for the error?
> I'll probably try that between T3 and -15.
>
> Thanks,
>
> Joachim
>
> [Non-text portions of this message have been removed]
>
>



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

Cut the carbon track and carefully place an 82k resistor in it's place. Do this as long as you are reading anything from about 13-14.98 volts from the wire going to the TSB board. If you see pressure working there is nothing wrong with the board.

Sent from my iPad

On 19 May 2013, at 12:58, "Robert Stewart" <bob@...> wrote:

> OK. Just been looking at the pic, and the service manual.
> It could well be that the resistive print in that area is faulty either
> due to wear and tear, or just plain old age.
> Looking at the service manual it suggests that on either side of the
> contact resistor (topologically speaking) are some resistors. If you're
> feeling brave you try adding a new resistor into the path to compensate
> for the error?
>
> B
> On 19/05/2013 11:31, joachim.milson wrote:
>>
>>
>>
>> Thanks Bob for your answer.
>>
>> I already cleaned the boards and sensors carefully.
>> The contacts are very clean. I did it very carefully under a
>> magnifying lens. Also, I changed the sensor with an other one but the
>> issue is still there. So on my opinion, the problem is the PCB itself.
>>
>> Joachim
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>

The problem was solved by adding a resistor in parallel to the carbon
track resistor. (I did not have the needed value at hand that's why I
used two resistors) And now the AT works perfectly.

Here is a photo of the two resistors in place: AT Resistors
<http://groups.yahoo.com/group/yamahacs80/photos/album/1863574374/pic/10\
5926260/view>


Joachim



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

> Cut the carbon track and carefully place an 82k resistor in it's place. Do this as long as you are reading anything from about 13-14.98 volts from the wire going to the TSB board. If you see pressure working there is nothing wrong with the board.

I just finished soldering the resistors when I noticed your message. Thanks however for your suggestion.

Joachim

> Cut the carbon track and carefully place an 82k resistor in it's place.

I'm a bit curious how you got this 82k value. Measuring it directly, even when all the wires are unsoldered, is not possible since the various carbon tracks cannot be isolated from each other. Did you use a broken board?

Joachim