Service Manual MX300
Teledyne Analytical Instruments 42
3.9 Watchdog The MX300 is equipped with a watchdog circuit that continuously
monitors the electronics for proper operation. If the watchdog detects a
failure, one of the following codes will appear on the LCD.
The error codes can appear on the LCD when batteries are first
installed, during normal operation or if the unit is subjected to extreme
shock. In some cases an additional digit is used in the error code to
supply additional information. For example, the error code 6 and 7 are
followed by another digit listed as (N) in Table 3.2. The error code 65
would indicate that a key is stuck and this key is the Silence key.
In addition to supplying visual error codes, the audio device will
beep a number of times to indicate the general error in case the display is
not functional.
NOTE: To reset the watchdog error code. Remove one battery for
5 seconds and replace. If the error persists contact your
local representative or Teledyne for assistance.
Table 3-2 Error Codes
Error Code Audio Beeps Error
Indeterminate 2 The watchdog timer has timed out indicating a
serious software error
30 3 Analog output is different from the expected value.
May indicate a shorted or over-loaded analog
output or a failure of the analog to digital converter
or digital to analog converter circuit.
50 5 The ADC circuit failed during POST.
6 (5) 6
(There is no
indication of
which key is
stuck)
A stuck key has been detected. The second digit
example (5) on the display shows which key is stuck:
0 - Low Alarm
1 - Batt
2 - Cal
3 - Up
4 - Down