The backlight had long since failed on my K5000R in the studio. I'm rather fond of this curious additive "secret weapon" so since I had a good outcome retrofitting my SY/TG77s with modern high contrast white on blue displays I started to wonder if I could do the same with the K5000R.
On dismantling the synth and consulting the service manual the original display turns out to be a 240 by 64 dot display with a Toshiba T6963C compatible driver IC on a 20 pin two row IDC header with a high voltage electroluminescent backlight.
I managed to find a company on eBay in China selling a blue display with remarkably similar dimensions with the usual exception with LED backlit displays that it's considerably deeper than the original.
The part number is: (HSM) LCM24064B (If anyone is interested I'll post a link to the supplier)
Cross comparing the datasheet with the schematic revealed an almost identical pinout.
Well after much fiddling around - I managed to make it work!!
There are a number of gotchas that make this project a little tricky...
These are my notes and do not constitute a full installation so please treat as some guidelines for experienced engineers only.
The EL backlight driver needs to be disabled by removing the power transistor (Q2) that drives it (this will cut down noise). Then the white EL backlight cable removed.
The display first needs to be fitted with a 2x18 pin header with the header justified towards the pin 1 end. This very deliberately leaves pins 19 and 20 on the original ribbon cable not connected - I LEARNT THIS THE HARD WAY THAT THESE PINS MUST NOT BE CONNECTED!!
A 2 Pin header is fitted in pins 21 and 22 on the lcd panel. These are wired to the 5 volt rail for the LED backlight - the floppy disk cable is an easy place to pickup 5 volts. Pin 21 is positive (LED Anode) and 22 Cathode.
There are suitable dropper resistors already on the display so no current limiting is required.
There is also a solder link that needs to be changed to put the controller in the correct mode:
Unsolder link J2 and solder J1 instead.
On removing the original display - the 4 display support standoffs need to be removed as the new display must fit much lower in the front panel chassis.
Warning: The top centre tapped screw hole to hold the aluminium front panel in place must be pressed flat and the screw discarded as otherwise it fouls the edge of the new display pcb!
Since the display has to fit very close to the metal panel the 6MHz crystal on the new display must be removed and relocated parallel to the 22 pin display header as there is a large cutout in the metal chassis at this point to permit it to poke through. I glued the crystal upside down at this point on top of an insulating strip and wired the leads back to the pads where the crystal used to be located.
I then lined the metal chassis plate under the display area with insulating tape and fitted the new display complete with 2 pin cable for the 5 volts to the backlight using four 12mm M3 screws. These screws must be only slightly torqued up or the pcb will bend as the display bottoms out on the metal flanges that hold the LCD bezel together.
On powerup you will find the contrast is wildly wrong and needs to be adjusted in the system menu.
A Quick Test Fitment...
Front Panel Back In Place and Looking Great!...
Its so clear now you can the display on the other side of the studio!!
