After a long break I’ve decided to retrofit my K2000R. I still had a few white-on-black displays on the shelf, purchased from artronic.eu:
The process was actually really easy. The new display has a 1-1 pin layout. No additional pull-up or down wires or resistors were required.
I desoldered the ribbon connector from the old display, and resolderded it onto the new display.
On the backlight driver board, I desoldered the Q1 driver transistor and transformer. The supply voltage to the backlight driver board is an odd 7V. I decided to use an 100Ohm resistor in series. At 80mA the drop voltage will be around 4V, leaving 3V for the LED backlight.
I shorted the VCC to a (former) transformer pin, from which the resistor guides the current to the backlight LED.
The contrast was quite a bit of after replacement, but the range in the menu is quite large, so dialing it down from +14 to -20 did the trick.
On the pictures the image looks white on blue, but it actually is white on black. I’m very happy with the result!