Kawai Synthesizers

So I have downloaded Service manual and checked the schematics.  
There's no PSU inside, just external power supply. But you can check  
voltages in power stabilizing circuit after U22, U23, U24,  
electrolytic capacitors around them, and there's also fuse - I would  
start with this one :-)

LCD has here only 15 wires, modern displays in this HD44780 standard  
have 16. Here Cathode is on pin 15 (not 16), and probably Ground for  
backlight is common. But you have schematics as well, and experience  
with electronics and soldering, so you know all this.

Contrast can be set on pin 3. Try to use different value for limiting  
resistor R3 to get voltage around or under 4 Volts.

Daniel Forro


On Jan 19, 2015, at 2:53 AM, evang.paul@... [kawaisynths] wrote:

> Glad to see there are other out there with this little classic. I  
> bought a K4 (not K4r) a few years back as a part of a bundle deal  
> from a friend. It was in used but working order and it saw a couple  
> years of use from me too, and all was well.
>
> Then, I started building a Midi Controller following some plans  
> online, and needed a 2x16 character LCD for the project. So, being  
> cheap and crafty at the time, I said to myself, rather than buy one,  
> why not just borrow the one from inside the K4. That worked out at  
> the time.
>
> Fast-forward approx 10 years, and I want to restore that K4 to its  
> original glory and use it as a keyboard once again. Problem is, I  
> can't find the original LCD or midi controller project anywhere...
>
> So, a couple weeks ago I ordered the exact replacement off of eBay.  
> While waiting for the replacement to come in, I opened the thing up  
> and saw that the button-cell battery had leaked, so I replaced it  
> (yes, i know, big no-no). Then, i received the LCD, made an  
> improvised ribbon cable with an old IDE cable i had, and soldered  
> one end to the LCD and connected the other end to the board  
> following the 1:1 pinout i saw on the schematic i have.
>
> Now, I turn the unit on, the LCD turns on/green backlight, however  
> NOTHING else happens. No message at all on the display and, when  
> connecting headphones to the audio outs, nothing is heard when keys  
> are pressed.
>
> I just read in the other LCD thread that, if the battery is removed  
> while the unit's unplugged, this causes a loss of data. Now, is this  
> what's affecting me, or is there a greater issue?
>
> Any input would be greatly appreciated!!!!
>