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Troubleshooting Model GFC7000TA Carbon Dioxide Analyzer
Teledyne Analytical Instruments 249
10.5.9. CPU
There are two major types of failures associated with the CPU board: complete failure and a failure
associated with the Disk on Module (DOM). If either of these failures occur, 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.
10.5.10. RS-232 Communications
10.5.10.1. General RS-232 Troubleshooting
Teledyne Instruments analyzers use the RS-232 communications protocol to allow the instrument to be
connected to a variety of computer-based equipment. RS-232 has been used for many years and as
equipment has become more advanced, connections between various types of hardware have become
increasingly difficult. Generally, every manufacturer observes the signal and timing requirements of the
protocol very carefully.
Problems with RS-232 connections usually center around 4 general areas:
1. Incorrect cabling and connectors. See Section 6.11.2 for connector and pin-out information.
2. The BAUD rate and protocol are incorrectly configured. See Section 6.10.7.
3. If a modem is being used, additional configuration and wiring rules must be observed. See
Section 6.13.2.6
4. Incorrect setting of the DTE – DCE Switch is set correctly. See Section 6.10.5
5. Verify that cable (03596) that connects the serial COM ports of the CPU to J12 of the
motherboard is properly seated