KawaiK3Zone

Amazing job, Elliot, congrats...  I opened up my CZ101 to change the LCD,
took one look & said 'screw that', & put it back together...  wanna do me a=
 
favor?
jonboy

--- In kawaik3zone@yahoogroups.com, Stuart Williams <netbrowserman@y...> 
wrote:
> 
> 
> 
> 
> 
> Hey ppl
> 
>  
> 
> I thought I would share with you some experience I had with a very long t=
erm 
repair of my Kawai K3 synth.  Want to know what the longest running repair =

job is on a K3 ?
> 
>  
> 
> My repair started about 10 years ago.  I had a strange overheating proble=
m 
with K3, it would play all sorts of strange noises once it had heated up, t=
akes 
around 2 hours or so to overheat.  I would then experience strange irregula=
r 
sounds being generated, and the LEDs would flash erratically.
> 
>  
> 
> With the K3 running, I did a bit of flexing and tapping.  I pulled all th=
e boards 
out and examined the boards for cracks, and checked for bulging caps.  
Discovered a small crack on the lower PCB closest to the power supply, this=
 
was effecting one segment of the LED display!   I repaired this track, and =
the 
LED display segment came up good.  I waited for the K3 to heat up, to see i=
f 
this fixed the other problem and experienced the same random noises etc.  T=
he 
boards had many dry solder joints, I would suggest a reflow to anyone who h=
as 
not done so recently on the K3.  I replaced most of the components on the 
power supply and checked and pushed nearly everything I could!
> 
>  
> 
> I found that around the processor board, near the processor, it was very =

sensitive to heat.
> 
>  
> 
> The processor is an Intel 8031P manufactured in 1980 (by many companies; =

Sanyo, Philips, Intel, MHS), its an 8-bit Microprocessor in the family of t=
he 
8051, 8052, 8054, 8058, 8751, 8752, 8754, 8758, 8032 which later evolved 
to  8086, 80x86....  
> 
>  
> 
> The processor does everything, controls the display and runs the K3 
operating system, ie. You press a button and you control another part of th=
e 
synth.  Its quite amusing to think there is a whole operating system (OS) i=
n 
there chugging away.
> 
>  
> 
> Looking at the specifications for around then, it was NMOS technology.  I=
 
suspected the processor was faulty so I sourced a replacement.  I do not kn=
ow 
a great deal about the manufacturing, but I know that CMOS reduces the heat=
 
vastly, and there is an 80C31 CMOS processor that will operate at the same =

voltage/pin specification as the original NMOS 8031 at half the density, wh=
ich 
means a lot less heat.  You can easily find the datasheets and verify that =
it is 
a suitable replacement.
> 
>  
> 
> I desoldered the original 8031 and replaced it with a socketed shiny new =

80C31 processor.  I fired up the K3..... and DEAD!.  Nothing at all on the =
display. 
After all this it did not work at all – bullocks I say...
> 
>  
> 
> I went over more of the Philips 80C3X datasheets and realized the K3 may =
be 
configured to clock in the wrong way, what this thing needs is XTAL1 juice.=

> 
>  
> 
> On the 80C31 pins 18 XTAL2 and 19 XTAL1 need to be swapped.  Pin 18 shoul=
d 
not be connected, ie. Do not ground it like the K3 does, clock the pin 19 i=
nstead 
(where pin 18 was connected on the board).  This is very easy to fix with a=
 DIP 
socket.  You can simply lift out pin 18 and bend pin 19 across to fill its =
place.
> 
>  
> 
> The K3 now runs at a very low temperature, I ran it all day and all night=
 with 
the new 80C31.  It has been running now for a couple of weeks with no heat =

problems or random noises.  The original processor was a power pig, this 
processor uses a lot less power -- CMOS replacement may be a solution to 
other peoples heat / power consumption problems on the K3?
> 
>  
> 
> Regards,
> 
> Elliot
> 
> 
> 
> 
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