ITT GX240 Metrix Function Generator

[Orion63]

Hi, I have this ITT GX240 Metrix Function Generator with Frequency counter. It has developed a display problem as shown in the attached picture. All the functions are working alright. Even the digits are displayed correctly, except that the segments G,E and C does not illuminated on the display. I tried taking out the LCD module (40-pin) and cleaning the contacts but was not successful. Could it be a display driver issue or LCD issue  ? I don't think it is Microprocessor issue as the data is sent correctly to the Display unit. Any help from the forum is appreciated. Thanks for looking.

[shakalnokturn]

To check the driver IC without schematics you'd have to scope all the outputs to the LCD, normal driving levels are (close to) 0V, (close to) Vcc, Vcc/3 and 2Vcc/3.

What can also happen with those LCD's is that one of the glass-metal "F" shaped contacts becomes loose.
Try applying some pressure to the LCD or contacts individually while it's working see if it makes any difference.