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FuchsMicro

Wavestation Mod

If you happen to own a Korg Wavestation EX or Korg Wavestation A/D sooner or later you will face the problem of a dying LCD Backlight.

Now you're left with two options:
1) Replace the Backlight LE Foil with a new one and stay with the bad viewing angle and the inverter whine.
2) Replace the whole display with a LED version and get rid of all the annoying stuff.

After Cheetah and EIsfuchs did the first option a couple of years ago I now took on the second, after the inverter whine drove me crazy when working with the old Korg Lady a whole day in my studio.

So thanks to the internetz I found http://tellun.com/wavestation/wavestation.html
The Mod is for the A/D but since I know that the A/D And the EX are exactly the same System on the inside I decided to try it on the EX.


This Mod is not for beginners.
You must have a decent level of experience in soldering electronics and know about ESD-protection an all that stuff when handling microprocessors.
Also this is a kind of "vintage" instrument. Some parts are nearly impossible to replace if broken! So use extreme care when taking this old lady apart. And you will have strip her to the bones, so here we go.

01
The Wavestation EX (on top of a Kurweil PC88mx)

02
The original LCD Display with EL-Foile backlight and the singing inverter

03
Working on the wavestations means S-C-R-E-W-S! Lots of them! So after you removed the 18 screws to open the casing. you're warmed up to dig deeper.

04
On the central PCB you find the 20-pin ribbon-cable header (left) that connects to the display far below

05
Take out the main PCB and the Audio/Midi PCB

06
Unscrew the tin-foil on top of the keyboard and the tin-cover over the mod wheels and take out the keyboard

07
empty eh? ...  take out the tin-foil completely (more srcews) -

09
 welcome to the buttons PCB - leave the golden screws in place but remove the black ones (4 screws)

10
Finally home. Dhis is the display. Unscrew the 4 corners and take it out.

11
Here we have the old LCD (left) and the new LED one (right)

12
And the back. Old on left side, new on right side.

13
Lets start preparing the new one:
There's enough space to put a pin connector for a ribbon cable on, so let's do it.

You realize that only 18 of the 20 connections are on the pin block. This is because pin 19 is the font-select that needs to be pulled up permanently by VDD to give a 6x8 font (like the original Wavestation display) and pin 20 is NC.
Pin 9 supplies -11V for contrast adjustment, but since we like to use the contrast control on the back of the Wavestation we don't need that. That's why this is cut on the terminal-block.

14
Here you see the jumper cable that pulls up Pin 19 (Font-Select) and one resistor of the voltage divider that matches the original contrast control voltage to the new display (the second one is in the ribbon cable that runs from the main PCB display header)

15
I reused the original cable fro the backlight here. Black - Ground - goes to K (Kathode); White - +5V VDD - goes to A (Anode)
You can also grab that from the main pin connector. But I decided to go with this way since I want to modify the power supply anyway.

16
This is the power supply PCB. The green transformer down right is the one that creates that awful whine in the inverter circuit.

17
noisy bastard ...


18
take it out!

19
The resistor (100 ohm) connects the terminal to +5V VDD and limits the current to the LED display. I put a little bit of heat shrink on just to be save.
The other Pin of the Terminal is already connected to GND.
The middle one is NC.

20
Et Voilá! New display backlight running.

21
After another 90 minutes reassembling time and myriads of screws you finally get - this! (hopefully)



22
The display is now inverted (white font on dark blue background) ... and it's bright! Even I'm only giving it about 20mA (it's rated for 100mA! And the synth is now completely silent :)

Hopefully this will last for the rest of the wavestation's life.
But since all (except the power supply) adoptions are made on the new display It's easy to swap back to the original one (or yet another)

Comments

Re: Resistor whine

It's not a resistor that produces the noise but the step-up transformer of the inverter circuit needed for the original back-light.
I'm not the designer of that circuit board, but since it's on the same PCB as the power supply I'd not use any insulation there. It's a design flaw that get's worse as the components age. So my way was to swap the whole display to something more "state of the art".