Teledyne 9110EH - Nitrogen Oxides Analyzer - Manual (Page 211)

Model 9110EH Instruction Manual Troubleshooting & Repair
Figure 11-3: Motherboard Watchdog Status Indicator
11.1.4.2. CPU Status Indicator
The CPU board has two red LEDs, the lower of which is the watchdog timer (the device that
pulses the motherboard watchdog). This LED is labeled LED2 and blinks about twice per
second (twice as fast as the motherboard LED) when operating normally. LED1 above LED2
should always be on. However, both CPU LEDs only indicate if the CPU is powered up
properly and generally working. The lower LED can continue to blink even if the CPU or
firmware are locked up.
11.1.4.3. Relay Board and Status LEDs
The most important status LED on the relay board is the red I 2 C Bus watch-dog LED,
labeled D1, which indicates the health of the I 2 C communications bus. This LED is the left-
most in LED row 1 in the center of the relay board when looking at the electronic compo-
nents. If D1 is blinking, then the other LEDs can be used in conjunction with the DIAG
menu I/O functions to test hardware functionality by manually switching devices on and off
and watching the corresponding LED go on or off.
Figure 11-4 illustrates the relay board layout including the two rows of LEDs, Table 11-2
lists the individual LED functions and the menu tree below shows how to access the manual
control of the I/O functions. Note that only some or the LEDs may be functional in your
analyzer model; the relay board layout is conceptualized for spare, future functionality and
is also common to many of the E-series analyzers.
M9110EH Rev 0 197