Yamaha CS80

Hello,
This is my first post here so - Hello everybody! My name is Tobias and last weekend I fulfilled my long time dream of getting (and actually playing for the first time) a Yamaha cs80. Unfortunately initial deep tests revealed two flaws of my machine - I have no aftertouch on middle G key and no sawtooth wave on voice1 card (channel 1). There are noise and square so I don't think it's a VCO or VCF or VCA chip. On the other cards at all channels everything seems to work fine. Anybody have an idea what it might be? Thanks in advance!

Sounds like you have a faulty waveshaper on channel one. I don't have the
service info in front of me so can't guide you through it.
If you're confident opening it up, I'd remove the M card for that voice
from the frame and put a scope on the triangle out of the waveshaper
chip and see if you're getting anything.
If you are, trace the signal with the aid of the schematic up to the switch
and so on to see where it disappears.
AT fault with either be a faulty sensor, or a faulty chip. Again if your
confident opening it up, I'd trace the AT signal from the key sensor, and
trace it back.
If you're not sure about opening it up, get someone who knows CS series to
have a look. These are sensitive machines, so you have to show a bit of
respect when poking around.

Hope that helps.

On Tuesday, May 21, 2013, pyjamagroove wrote:

> **
>
>
> Hello,
> This is my first post here so - Hello everybody! My name is Tobias and
> last weekend I fulfilled my long time dream of getting (and actually
> playing for the first time) a Yamaha cs80. Unfortunately initial deep tests
> revealed two flaws of my machine - I have no aftertouch on middle G key and
> no sawtooth wave on voice1 card (channel 1). There are noise and square so
> I don't think it's a VCO or VCF or VCA chip. On the other cards at all
> channels everything seems to work fine. Anybody have an idea what it might
> be? Thanks in advance!
>
>
>


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

Yes it does sound like it is a bad IG00158 waveshaper chip. I have them if you need one.
Doug
synthparts.com

--- In yamahacs80@yahoogroups.com, Bob Stewart <bob@...> wrote:
>
> Sounds like you have a faulty waveshaper on channel one. I don't have the
> service info in front of me so can't guide you through it.
> If you're confident opening it up, I'd remove the M card for that voice
> from the frame and put a scope on the triangle out of the waveshaper
> chip and see if you're getting anything.
> If you are, trace the signal with the aid of the schematic up to the switch
> and so on to see where it disappears.
> AT fault with either be a faulty sensor, or a faulty chip. Again if your
> confident opening it up, I'd trace the AT signal from the key sensor, and
> trace it back.
> If you're not sure about opening it up, get someone who knows CS series to
> have a look. These are sensitive machines, so you have to show a bit of
> respect when poking around.
>
> Hope that helps.
>
> On Tuesday, May 21, 2013, pyjamagroove wrote:
>
> > **
> >
> >
> > Hello,
> > This is my first post here so - Hello everybody! My name is Tobias and
> > last weekend I fulfilled my long time dream of getting (and actually
> > playing for the first time) a Yamaha cs80. Unfortunately initial deep tests
> > revealed two flaws of my machine - I have no aftertouch on middle G key and
> > no sawtooth wave on voice1 card (channel 1). There are noise and square so
> > I don't think it's a VCO or VCF or VCA chip. On the other cards at all
> > channels everything seems to work fine. Anybody have an idea what it might
> > be? Thanks in advance!
> >
> >
> >
>
>
> [Non-text portions of this message have been removed]
>

If you're lucky, both issues can be explained by two loose/broken wires.

No sawtooth: look at input G2(44) of the M board on the overall circuit diagram. This wire selects whether the Saw signal is used or not. If it's broken, you get no SAW. If the wire is OK, you might check FET6. Consider changing the waveshaper (IG00158) only as a last resort.

No aftertouch: check the wire from TSB2 (or TSB1) to the TKC (both boards are located below the keyboard, on the right side. The wires are not set around the board in the order of the notes. So you'll need the service manual to determine which one is for the middle G. But if the wire is broken, you should find it easily! I had one such problem with a wire that broke under the stress. And a mere solder solved the problem.

Also, be very gentle while removing the M board. It's so easy to inadvertently draw (and break) some wires of the board close to it. That's so thick therein !

Joachim

my guess is at or after the saw output on the waveshaper chip.. if you have square working, that out on the waveshaper is working..meaning the inverse saw feeding it from the osc chip is working.

-----Original Message-----
From: pyjamagroove <pyjamagroove@...>
To: yamahacs80@yahoogroups.com
Date: 05/21/13 03:34
Subject: [POSSIBLE SPAM] [yamahacs80] Need help with no sawtooth wave on voice 1 channel 1 card and one G key aftert.

     
Hello,
This is my first post here so - Hello everybody! My name is Tobias and last weekend I fulfilled my long time dream of getting (and actually playing for the first time) a Yamaha cs80. Unfortunately initial deep tests revealed two flaws of my machine - I have no aftertouch on middle G key and no sawtooth wave on voice1 card (channel 1). There are noise and square so I don't think it's a VCO or VCF or VCA chip. On the other cards at all channels everything seems to work fine. Anybody have an idea what it might be? Thanks in advance!









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

always remember to power off the CS80 and lay a cloth or towel down on the keybed  frame before attempting to remove a M card from the rack rails... those rails are live with voltage and can ruin other things ... especially important for a first time peek inside CS80 ....................................................!!! 
-----Original Message-----

> From: "Bob Stewart" <bob@...>
> To: yamahacs80@yahoogroups.com
> Date: 05/21/13 03:53
> Subject: [POSSIBLE SPAM] Re: [yamahacs80] Need help with no sawtooth wave on voice 1 channel 1 card and one G key aftert.
>
> Sounds like you have a faulty waveshaper on channel one. I don't have the
> service info in front of me so can't guide you through it.
> If you're confident opening it up, I'd remove the M card for that voice
> from the frame and put a scope on the triangle out of the waveshaper
> chip and see if you're getting anything.
> If you are, trace the signal with the aid of the schematic up to the switch
> and so on to see where it disappears.
> AT fault with either be a faulty sensor, or a faulty chip. Again if your
> confident opening it up, I'd trace the AT signal from the key sensor, and
> trace it back.
> If you're not sure about opening it up, get someone who knows CS series to
> have a look. These are sensitive machines, so you have to show a bit of
> respect when poking around.
>
> Hope that helps.
>
> On Tuesday, May 21, 2013, pyjamagroove wrote:
>
> > **
> >
> >
> > Hello,
> > This is my first post here so - Hello everybody! My name is Tobias and
> > last weekend I fulfilled my long time dream of getting (and actually
> > playing for the first time) a Yamaha cs80. Unfortunately initial deep tests
> > revealed two flaws of my machine - I have no aftertouch on middle G key and
> > no sawtooth wave on voice1 card (channel 1). There are noise and square so
> > I don't think it's a VCO or VCF or VCA chip. On the other cards at all
> > channels everything seems to work fine. Anybody have an idea what it might
> > be? Thanks in advance!
> >
> >  
> >
>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>

On 5/21/2013 3:34 AM, pyjamagroove wrote:

> Hello,
> This is my first post here so - Hello everybody! My name is Tobias and last weekend I fulfilled my long time dream of getting (and actually playing for the first time) a Yamaha cs80. Unfortunately initial deep tests revealed two flaws of my machine - I have no aftertouch on middle G key and no sawtooth wave on voice1 card (channel 1). There are noise and square so I don't think it's a VCO or VCF or VCA chip. On the other cards at all channels everything seems to work fine. Anybody have an idea what it might be? Thanks in advance!
>

Educated guess here is the analog switch to select the ramp waveform
has failed. It is called "FET6" on the M board. The vintage part
number is 2SK30, but just about any N-channel JFET will work here.
2N3819, BF245, J112, etc. Just observe the pin order.

Crow
/**/

Wow, this group is amazing! So many responses in such a short time - Thanks a lot guys! I'll try to test it following your advices.

Just a little update.
1. For the missing sawtooth wave I´ve checked the G2 wire - it´s ok and the FET6 transistor also ( I´ve changed it anyway just in case). Seems like it`s the waveshaper chip after all.....
2. For the missing G note aftertouch I´ve checked all the wires on the AT boards and they seem ok. Is it possible that the sensor´s broken or dirty?

> 1. For the missing sawtooth wave I´ve checked the G2 wire - it´s ok

When you say that it's OK, do you mean that you can measure some voltage at G2 when the SAW switch is on and nothing when it's off, or is it only based on a visual check?
There's also the transistor TR6 that you might check before discarding IC9.

> 2. For the missing G note aftertouch I´ve checked all the wires on the AT boards and they seem ok. Is it possible that the sensor´s broken or dirty?

I don't know if those sensors can be broken (has anyone ever seen one broken?): I cleaned mine recently ; a few were a bit dirty but none had sign of wear. With a swap, you should be able to determine if there is a problem with the sensor.

Joachim

> When you say that it's OK, do you mean that you can measure some voltage at G2 when the SAW switch is on and nothing when it's off, or is it only based on a visual check?
> There's also the transistor TR6 that you might check before discarding IC9.

It was a visual check of G2.....Ill try to measure it.

Can TR6 be replaced by 2N 3819 transistor I used to change FET6 ?

I´m sorry if it´s a silly question but I would like to know about that transistor - Can Tr6 be replaced by 2N 3819 ? ( I don´t know much about electronics - I just can replace components without destroying everything ;).

--- In yamahacs80@yahoogroups.com, "pyjamagroove" <pyjamagroove@...> wrote:
>
>
> > When you say that it's OK, do you mean that you can measure some voltage at G2 when the SAW switch is on and nothing when it's off, or is it only based on a visual check?
> > There's also the transistor TR6 that you might check before discarding IC9.
>
> It was a visual check of G2.....Ill try to measure it.
>
> Can TR6 be replaced by 2N 3819 transistor I used to change FET6 ?
>

> I´m sorry if it´s a silly question but I would like to know about that transistor - Can Tr6 be replaced by 2N 3819 ? (I don´t know much about electronics - I just can replace components without destroying everything ;)

Sorry, but I'm no electronics guru neither. The reference for the Tr6 transistor is 2SA561. You could try a search for a replacement.

Joachim

Well, it was the waveshaper after all. Now that voice is rocking saw again. Thanks everyone.