Martel Electronics BetaGauge 3II - Manual (Page 61)

User Preferences 4-6
3. Press the menu items Light or Dark as many times
as necessary to adjust the LCD contrast.
4. When you have completed setting the contrast,
press the CLR key to return to the LCD menu.
5. Press the CLR key again to return to the Setup
menu.
Recovering the LCD Contrast
Extreme hot and/or cold temperatures can affect the
LCD contrast. If your calibrator is exposed to either of
these conditions, or if for any other reason, your LCD is
too light or too dark, you can restore the display even if
you cannot read it.
To recover the LCD contrast, do the following:
1. Turn the calibrator on and wait five seconds for
initialization.
2. Press the MENU key twice.
3. Press the F1 key.
4. Press the F2 key.
5. Do one of the following:
 If the display is dark, press F1 repeatedly until
the display is visible.
 If the display is light, press F2 repeatedly until
the display is visible.
NOTE: The contrast will wrap around until it is
visible, regardless of which function key you press.
6. Turn the calibrator off and on again to verify that
the contrast has been recovered.