75C Display Contrast Adjustment?

[Sylvain Cote]

(10-06-2014 11:25 PM)cruff Wrote:  I've just acquired a 75C, it would be nice if there was a way to adjust the display contrast a bit. I didn't find anything in the manuals. Has anyone figured out a method for a hardware adjustment?

The LCD of the 75 cannot be software adjusted like the 71B.

The only way to change the contrast is to disassemble the unit and follow the procedure of the HP-75 Service Manual.

LCD electronic design - Service Manual Page 2-29/30
LCD contrast adjustment procedure - Service Manual Page 5-11

I have not tried the procedure, so I would be cautious doing it.
Like any electronic tampering, you can potentially damage your unit.

Best regards,

Sylvain