|Re: HP 28s display problem|
Message #2 Posted by C.Ret on 15 Jan 2009, 2:46 a.m.,
in response to message #1 by Fred Herring
Sorry, I am not sure my post will be of great help !
I don't know any way using the line command or any system subroutine call to adjust the display contrast. This will not prouve that there not such a way.
Since the unit operates perfectly otherwise, I will assume that the key contact of the ON, + and - keys are correctly operating as well.
Unit turn OFF/ON easily, ON key interrupt programs, + and - oparate,...
In such a circumstance, low contrast display may only be interpreted as a consequence of a low batteries level (old batteries, one inverted battery or bad/dirty contacts).
Another cause may be low temperature of the unit, the LCD or the battery cells.
I already encounter such low contrast symptom after a software crash. Resetting the unit clear the defect.
If battery and temperature is OK and several resets don't help, then a defective LCD electronic have to be suspected.