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T400 Ozone Analyzer Operator’s Manual Troubleshooting & Service
253
12.3. USING THE INTERNAL ELECTRONIC STATUS LEDS
Several LEDs are located inside the instrument to assist in determining if the analyzers
CPU, I
2
C bus and Relay PCA are functioning properly.
12.3.1. CPU STATUS INDICATOR
DS5, a red LED, that is located on upper portion of the motherboard, just to the right of
the CPU board, flashes when the CPU is running the main program loop. After power-
up, approximately 30 – 60 seconds, DS5 should flash on and off. If characters are
written to the front panel display but DS5 does not flash then the program files have
become corrupted, contact customer service because it may be possible to recover
operation of the analyzer. If after 30 – 60 seconds, neither DS5 is flashing nor have any
characters been written to the front panel display then the CPU is bad and must be
replaced.
Motherboard
CPU Status LED
Figure 12-2: CPU Status Indicator
12.3.2. RELAY PCA STATUS LEDS
There are sixteen LEDs located on the Relay PCA. Some are not used on this model.
12.3.2.1. I
2
C Bus Watchdog Status LEDs
The most important is D1 (see, which indicates the health of the I
2
C bus.
Table 12-4: Relay PCA Watchdog LED Failure Indications
LED Function Fault Status Indicated Failure(s)
D1
(Red)
I
2
C bus Health
(Watchdog Circuit)
Continuously ON
or
Continuously OFF
Failed/Halted CPU
Faulty Motherboard, Valve Driver board or Relay PCA
Faulty Connectors/Wiring between Motherboard, Valve
Driver board or Relay PCA
Failed/Faulty +5 VDC Power Supply (PS1)
If D1 is blinking, then the other LEDs can be used in conjunction with DIAG Menu
Signal I/O to identify hardware failures of the relays and switches on the Relay.
06870C DCN6332