Sort of mostly followed this vs the tellun process, but couldn’t figure how you were getting the R2 & R3 changes to yield a proper contrast voltage (~7.5V) at pin 4. Also I have an alpha Juno-2 with an 1×16 charachter LCD displayfor which I found a really nice OLED replacement 🙂 Stay tuned for the report on these! Post navigation so I´ll think this one will be next in line. I have a Kurzweil K2000R, Kawai K5, Korg 01/W, Yamaha TG/77 and a Roland D70 which all have the same type of (failing) 240×64 display, wating for a overhaul 🙂 The D70 is in the worst shape with the annoying whine audible in the output signal. put everything together and close the unit up.solder an 100Ohm resistor from the + lead of C49 to the pin feeding the EL backlight (see ).remove mainboard and desolder the EL transformer TR1.replace resitors R2 and R3 with new resitors valued 3k9 and 6k8.remove the front PCB, and desolder resistors R2 and R3.connect connector pin 19 to pin 3 on the display.desolder 20-pin ribbon cable PCB connector and EL backlight power leads from old Optrex display.make photo’s of the screws mounting components and boards, these will be useful when screwing everything back together 🙂.I reused the wires from the EL feed to power the LED backlight from the mainboard, adding a 100 Ohm resistor from the +5V rail, as described in tellun’s guide.Įxcellent result with little costs and a few minor alterations. So, replacing the resistors is an easy job and voids the need of cutting a wire or adding resistors to the display.Īll whats left to do is remove the transformer feeding the EL backlight on the old Optrex display, to eliminate the high pitched noise. While most of the electronics on the mainboard are surface mount, the contrast control is located on the front-panel PCB which is fully through-hole. I determined (using some obscure math) values of 6k8 and 3k9 for resp the resistors R2 and R3 give me approximately this range. So ideally the contrast control circuit should work in the range of 2k5 and 4k5. I found that (while adding additional resistors in series) a resistance of 3.6kOhm gives ideal contrast. Sort of, because there is no connection to ground, making it just a variable resistor in the range of 0,7k to 2k5 between the LCD contrast pin and the -12V rail. Doing a little reverse-engineering on the contrast control of the Wavestation reveals it is build around a potentiometer and two resistors (VR1, R2 and R3), a sort of voltage divider fed by -12V. The tellun guide suggest adding an additional resistors as a voltage divider to lower the contrast control voltage range. I bridged pin 3 (+5V) and 19 on the display. The pin is open on the mainboard, maybe it is internally pulled high on the Optrex. The latter I find strange as the original Optrex display also has font selection on Pin 19. Powering the unit on I found the contrast signal range was way too high (as mentioned in the guide), and the font size was off (also mentioned in the guide, suggesting Pin 19 / font selection should be actively pulled high). The pinouts of both displays were identical so I was pretty convinced the new display wouldn’t burn out. Using an external power supply i powered the backlight LED as a test. First I desoldered the flatcable PCB connector from the old Optrex display and re-soldered it to the new LED display. I did however want to cut as little cables and add additional components as possible. I used this guide ( ) as a starting point. I find that it better matches the faceplates of most synths, (white on black), and it less bright in the studio without trading in readability. After some searching I decided to go with a white on black display, available from ARTRONIC (). A lot of people replacing their displays use the white-on-blue version, which looks really awesome.

There are some equivalent LED-backlit displays available from various (Chinese) vendors.

This type of display is used in A LOT of synths from that era. It contains a 240×64 pixels dot matrix display with T6963 compatible controller. I decided to start with the Wavestation A/D. Most of them suffer from the well known decaying Electroluminescence (EL) backlight problem, resulting in a barely visible screen, and a annoying high-pitched sound from the transformer powering the backlight. This week I started a project in which I want to replace the LCD screens in some of my synths.

Korg wavestation ad batterty