LCD Replacement The display on my unit was dim and hard to read, a common problem due to the LCD backlight wearing out, so I replaced it with a “Cool Blue” display part number JHD24064C that I also bought on ebay. Because the new LCD has a slightly different contrast bias spec than the original, the adjustment resistors were changed. The schematic excerpts below show the contrast adjustment pot on the “JK” board and the R195/R196 resistors on the “DM1” board. The new display has an LED backlight, so the inverter circuit on the “JK” board that powered the old EL (electroluminescent) backlight was disconnected. The new LED backlight is rated to connect directly to 5V and draw 120mA, but is too bright at those levels. Connecting the LED supply through a 22 ohm resistor reduced the current draw to 58mA, which is very close to the OEM EL inverter’s original current. The schematic excerpts below show where the inverter was disconnected and the new power leads were added.