Metrohm 726 Titroprocessor - Manual (Page 268)

13.1 13.1 Diagnosis Diagnosis
726 Titroprocessor, Instructions for use 262 262
13.1.3 To check display
With this diagnostic step the LCD and its control unit are checked for their functionality.
1. Prepare instrument for diagnostic test (see chap. 13.1.2).
2.
3.
Ä The background lighting goes out and so the screen text is only faintly visible.
4.
The control voltage for the dot matrix is switched off and so the screen is blank.
5.
Ä The background lighting is switched on and so the screen appears pale blue but with no text.
6.
Ä The control voltage for the dot matrix is switched on again and so the screen appears in its customary form.
7.
Ä The entire screen memory is checked for functionality. If a defect is found, an error message appears.
8.
Ä The screen controller is checked for functionality. If a defect is found, an error message appears.
9.
Ä The screen control system is initialised and so for a short time the whole screen is filled with stars and then goes
back to the previous screen text
10. The test is quit by pressing .
13.1.4 To check keyboard
With this diagnostic step all keys of the keyboard are checked for their functionality.
1. Prepare instrument for diagnostic test (see chap. 13.1.2).
2.
3.
4. Press all keys once.
Ä The keyboard is shown symbolically on the screen. When a key is pressed, the grey background of that key must
disappear. If a key is pressed repeatedly, a beep sounds. The test recognises if a key bounces, and an error messa-
ge is displayed. The special keys, and feature more than once on the keyboard and
the software is unable to recognise which one was pressed. Regardless of which key, for example, is
pressed, therefore, the one on the far left disappears first, and so on.
5. The test is quit by pressing the key twice.