The Kawai & Teisco Analog Synths Group

Hello,

I've got a corrupt SX-210 synth, and it wasn't the battery leakage
issue . Ok, battery is defective, too but seems, there's something
wrong with the sound board.

When I press a note on the keyboard, a the sound is somehow digitally
distorted, I can identify the instrument selected, but it sounds
awful. This phenomenon reduces but doesn't vanish, when I change the
LFO speed to nearly "00".
I took my oscilloscope to the test points of the single voices: noise
is  white, filters are working and each oscillator seems okay (clear
sine or triangle... wave), the voices downmix from oscillator section
is fine, too. 
BUT: If I measure the sound output before it reaches the "Ensemble"
board (the brown one left to the syn42) it is disorted. The waveform
looks, as if the audio-signal is modulated upon some random amplitude
rectangle pulse waveform at a continously changing frequency between
about 10 to 50 Hz. This looks very digital... and changes with
LFO-depth and speed. 
Where the F*ck is the LFO section? the only sections left on sound
board are four TC4051 multiplexers with opamps... guess they do some
signal mixing and switching...

Anyone schematics or ideas?

thank and best regs,

claudio

Does it happen on all voices ?

Someone on the vintagesynthrepair group has just noted about a 
spanish company sending him the schematics for SX240, you might be 
able to get the one for the SX210 too...

from his words:

"I get it from spanish official service 'Bilbao Trading' in Madrid."




--- In kawai-teisco@yahoogroups.com, "claudio" <claudio@...> wrote:
>
> Hello,
> 
> I've got a corrupt SX-210 synth, and it wasn't the battery leakage
> issue . Ok, battery is defective, too but seems, there's something
> wrong with the sound board.
> 
> When I press a note on the keyboard, a the sound is somehow 
digitally
> distorted, I can identify the instrument selected, but it sounds
> awful. This phenomenon reduces but doesn't vanish, when I change the
> LFO speed to nearly "00".
> I took my oscilloscope to the test points of the single voices: 
noise
> is  white, filters are working and each oscillator seems okay (clear
> sine or triangle... wave), the voices downmix from oscillator 
section
> is fine, too. 
> BUT: If I measure the sound output before it reaches the "Ensemble"
> board (the brown one left to the syn42) it is disorted. The waveform
> looks, as if the audio-signal is modulated upon some random 
amplitude

> rectangle pulse waveform at a continously changing frequency between
> about 10 to 50 Hz. This looks very digital... and changes with
> LFO-depth and speed. 
> Where the F*ck is the LFO section? the only sections left on sound
> board are four TC4051 multiplexers with opamps... guess they do some
> signal mixing and switching...
> 
> Anyone schematics or ideas?
> 
> thank and best regs,
> 
> claudio
>

Just a note, I found two bad 4066 chips on mine so far, it looks as 
if they are prone to fail oftenly on that instrument.




--- In kawai-teisco@yahoogroups.com, "claudio" <claudio@...> wrote:
>
> Hello,
> 
> I've got a corrupt SX-210 synth, and it wasn't the battery leakage
> issue . Ok, battery is defective, too but seems, there's something
> wrong with the sound board.
> 
> When I press a note on the keyboard, a the sound is somehow 
digitally
> distorted, I can identify the instrument selected, but it sounds
> awful. This phenomenon reduces but doesn't vanish, when I change the
> LFO speed to nearly "00".
> I took my oscilloscope to the test points of the single voices: 
noise
> is  white, filters are working and each oscillator seems okay (clear
> sine or triangle... wave), the voices downmix from oscillator 
section
> is fine, too. 
> BUT: If I measure the sound output before it reaches the "Ensemble"
> board (the brown one left to the syn42) it is disorted. The waveform
> looks, as if the audio-signal is modulated upon some random 
amplitude

> rectangle pulse waveform at a continously changing frequency between
> about 10 to 50 Hz. This looks very digital... and changes with
> LFO-depth and speed. 
> Where the F*ck is the LFO section? the only sections left on sound
> board are four TC4051 multiplexers with opamps... guess they do some
> signal mixing and switching...
> 
> Anyone schematics or ideas?
> 
> thank and best regs,
> 
> claudio
>

Thanks for your answer!

--- In kawai-teisco@yahoogroups.com, "gil_we" <gil_we@...> wrote:
>
> Does it happen on all voices ?

Yes, all voices are affected. I am wondering, what kind of waveform
should show on pin KCV on the sound board, I guess, a simple
rectangle, whose amplitude is magnifying by changing the KCV-value on
the User panel... but several times a second, there's an impulse in
the amplitude (same wavelength), its about 3V while the normal waves
ride at 2.5V.
Is this waveform connected to some addressable sample-hold thingy? if,
yes, there might be the problem...

how does a bad 4066 feel? how did you locate it?

 
> Someone on the vintagesynthrepair group has just noted about a 
> spanish company sending him the schematics for SX240, you might be 
> able to get the one for the SX210 too...

> "I get it from spanish official service 'Bilbao Trading' in Madrid."

Seems to be the only solution to try it, I'll scan and post it, when i
have a copy of the schematics

best reg, claudio

hey claudio,

it still sounds to me like a battery leakage related problem...

replace all components near the batter area and clean the board !

also, check connectors.




--- In kawai-teisco@yahoogroups.com, "claudio" <claudio@...> wrote:
>
> Hello,
> 
> I've got a corrupt SX-210 synth, and it wasn't the battery leakage
> issue . Ok, battery is defective, too but seems, there's something
> wrong with the sound board.
> 
> When I press a note on the keyboard, a the sound is somehow 
digitally
> distorted, I can identify the instrument selected, but it sounds
> awful. This phenomenon reduces but doesn't vanish, when I change the
> LFO speed to nearly "00".
> I took my oscilloscope to the test points of the single voices: 
noise
> is  white, filters are working and each oscillator seems okay (clear
> sine or triangle... wave), the voices downmix from oscillator 
section
> is fine, too. 
> BUT: If I measure the sound output before it reaches the "Ensemble"
> board (the brown one left to the syn42) it is disorted. The waveform
> looks, as if the audio-signal is modulated upon some random 
amplitude

> rectangle pulse waveform at a continously changing frequency between
> about 10 to 50 Hz. This looks very digital... and changes with
> LFO-depth and speed. 
> Where the F*ck is the LFO section? the only sections left on sound
> board are four TC4051 multiplexers with opamps... guess they do some
> signal mixing and switching...
> 
> Anyone schematics or ideas?
> 
> thank and best regs,
> 
> claudio
>

Hey, any news about this one ?....



--- In kawai-teisco@yahoogroups.com, "claudio" <claudio@...> wrote:
>
> Thanks for your answer!
> 
> --- In kawai-teisco@yahoogroups.com, "gil_we" <gil_we@> wrote:
> >
> > Does it happen on all voices ?
> 
> Yes, all voices are affected. I am wondering, what kind of waveform
> should show on pin KCV on the sound board, I guess, a simple
> rectangle, whose amplitude is magnifying by changing the KCV-value 
on
> the User panel... but several times a second, there's an impulse in
> the amplitude (same wavelength), its about 3V while the normal waves
> ride at 2.5V.
> Is this waveform connected to some addressable sample-hold thingy? 
if,
> yes, there might be the problem...
> 
> how does a bad 4066 feel? how did you locate it?
> 
>  
> > Someone on the vintagesynthrepair group has just noted about a 
> > spanish company sending him the schematics for SX240, you might 
be 
> > able to get the one for the SX210 too...
> 
> > "I get it from spanish official service 'Bilbao Trading' in 
Madrid."
> 
> Seems to be the only solution to try it, I'll scan and post it, 
when i

> have a copy of the schematics
> 
> best reg, claudio
>

--- In kawai-teisco@yahoogroups.com, "gil_we" <gil_we@...> wrote:
>
> Hey, any news about this one ?....

I'm sorry, but - no.
Well, I fixed it without schematics, it was one bad 4066 and one bad
4053 on the syn43 board. 

Thanks for your help :)
best regs, claudio

This is a common problem on the SX-210.

I had two bad 4066 in two different voices...



--- In kawai-teisco@yahoogroups.com, "claudio" <claudio@...> wrote:

>
> --- In kawai-teisco@yahoogroups.com, "gil_we" <gil_we@> wrote:
> >
> > Hey, any news about this one ?....
> 
> I'm sorry, but - no.
> Well, I fixed it without schematics, it was one bad 4066 and one bad
> 4053 on the syn43 board. 
> 
> Thanks for your help :)
> best regs, claudio
>