TROUBLESHOOTING & REPAIR PROCEDURES
Model 300E Carbon Monoxide Analyzer
Instruction Manual
208
P/N 04288 Rev: A
11.5.3.
I
2
C Bus
Operation of the I
2
C bus can be verified by observing the behavior of D1 on the
Relay Board in conjunction with the performance of the front panel display.
Assuming that the DC power supplies are operating properly and the wiring from
the Motherboard to the Keyboard, and the wiring from the keyboard to the Relay
board, is intact, the I
2
C bus is operating properly if:
§
D1 on the relay board is flashing, or
§
D1 is not flashing but pressing a key on the front panel results in a change to
the display.
11.5.4.
Keyboard/Display Interface
The front panel keyboard, display and Keyboard Display Interface PCA (03975 or
04258) can be verified by observing the operation of the display when power is
applied to the instrument and when a key is pressed on the front panel. Assuming
that there are no wiring problems and that the DC power supplies are operating
properly:
§
The vacuum fluorescent display is good if on power-up a “-“ character is
visible on the upper left hand corner of the display.
§
The CPU Status LED, DS5, is flashing, see Section 11.1.4.1.
§
If there is a “-“ character on the display at power-up and D1 on the Relay
Board is flashing then the Keyboard/Display Interface PCA is bad.
§
If the analyzer starts operation with a normal display but pressing a key on
the front panel does not change the display, then there are three possible
problems:
a. One or more of the keys is bad,
b. The interrupt signal between the Keyboard Display interface and the
motherboard is broken, or
c. The Keyboard Display Interface PCA is bad.
11.5.5.
Relay Board
The Relay Board PCA (04135) can be most easily checked by observing the
condition of the its status LEDs on the Relay Board, as described in Section
11.1.4.3, and the associated output when toggled on and off through Signal I/O
function in the Diagnostic Menu, see Section 11.1.3.