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T400 Ozone Analyzer Operator’s Manual Troubleshooting & Service
265
12.7.8.4. Control Inputs
The control input bits can be tested by applying a trigger voltage to an input and
watching changes in the status of the associated function under the SIGNAL I/O
submenu:
EXAMPLE: to test the “A” control input:
1. Under the DIAG SIGNAL I/O menu (See Section12.1.3), scroll through the
inputs a
nd ou
tputs until you get to the output named EXT_ZERO_CAL.
2. Connect a jumper from the
“+” pin on the appropriate connector to the “U” on the
same connector.
3. Connect a second jumper from the “” pin on the connector to the “A” pin.
4. The status of EXT_ZERO_CAL should change to read “ON”.
Table 12-11: T400 Control Input Pin Assignments and Corresponding
Signal I/O Functions
INPUT CORRESPONDING I/O SIGNAL
A EXT_ZERO_CAL
B EXT_LOW_SPAN_CAL
1
C EXT_SPAN_CAL
D, E& F NOT USED
1
Only operates if either Z/S or IZS option is installed
12.7.9. CPU
There are two major types of CPU board failures, a complete failure and a failure
associated with the Disk On Module (DOM). If either of these failures occurs, contact
the factory.
For complete failures, assuming that the power supplies are operating properly and the
wiring is intact, the CPU is faulty if on power-on, the watchdog LED on the
motherboard is not flashing.
In some rare circumstances, this failure may be caused by a bad IC on the motherboard,
specifically U57, the large, 44 pin device on the lower right hand side of the board. If
this is true, removing U57 from its socket will allow the instrument to start up but the
measurements will be invalid.
If the analyzer stops during initialization (the front panel display shows a fault or
warning message), it is likely that the DOM, the firmware or the configuration and data
files have been corrupted.
06870C DCN6332