Kawai Synthesizers

Hey everyone!

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!!!!

You can download factory program set from here:

http://www.kawaius.com/Downloads/download_archive-2.html

But if instrument doesn't show anything on the display, I can't  
imagine how to work with it - even in the case instrument itself is OK  
and there's just empty memory.

First be absolutely sure that display works. Maybe it's just contrast  
setting, maybe new display needs some other value of limiting  
resistor... Then you can continue.

In any case I would check and reseat all cables and IC's in sockets,  
after long years of sweet sleep contacts can be oxidized. Check also  
PSU if voltages are on the spec. Maybe you need to recap PSU...

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!!!!
>

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!!!!
>

I would focus on the LED contrast issue first...  the K4 may actually be working just fine, but you can't see anything on the display because the contrast is whack.  It is also possible you wired up the data connections incorrectly (even though you obviously got the backlight wired up okay).  So, double-check your work.
I did some experiments replacing the older-gen LCD screens on most of my gear with 16x2 displays -- and getting the contrast to work was always the most annoying part of the job.  I used a tiny 10K potentiometer (instead of a single resistor) so I could "dial-in" a working contrast after installation (much better to going back to re-solder the "correct" resistor, perhaps more than once :).
Ultimately though, I ended up using fancy new OLED screens for all my display "upgrades".  They look much better than even the most modern LCDs and don't need a contrast resistor!  OLED are much brighter and can be clearly read from almost any angle (in an OLED display, each pixel lights up individually and doesn't rely on a backlight or filtering through an LCD matrix).  IMO, OLED replacement displays are totally worth the cost ($20-40 instead of the $3 el cheapo LCDs you can get on ebay).
However...   I have yet to find an OLED screen that is compatible with my K4.  I've tried the Winstar and Electronic Assembly models (the EA models just seem to be re-branded Winstars).  Supposedly, all my devices use HD44780-compatible displays... but something about the K4 doesn't work with the Winstar (which is HD44780-compatible).  I've successfully installed OLED displays in a TX81Z, a Vintage Keys Plus, and an Alesis MMT-8.  I intend to upgrade my CZ-101 at some point as well.