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Model 400E Ozone Analyzer
Instruction Manual
11.5.7. CPU
There are two major types of failures associated with the CPU board: complete
failure and a failure associated with the Disk-On-Chip(DOC) on the CPU board. If
either of these failures occur, contact the factory.
1. For complete failures, assuming that the power supplies are operating properly
and the wiring is intact, the CPU is bad if on powering the instrument:
•
The vacuum fluorescent display shows a dash in the upper left hand corner
and,
•
There is no activity from the primary RS-232 port (COM-A) on the rear panel
even if "? <ret>" is pressed.
•
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 startup but the measurements will be incorrect.
2. If the analyzer stops part way through initialization (there are words on the
vacuum fluorescent display) then it is likely that the DOC has been corrupted.
11.5.8. RS-232 Communications
11.5.8.1. General RS-232 Troubleshooting
T-API 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:
•
Incorrect cabling and connectors. See Table 7–12 for connector and pin-out
information.
•
The BAUD rate and protocol are incorrectly configured. See Section 6.9.6.
•
If a modem is being used, additional configuration and wiring rules must be
observed.
•
Incorrect setting of the DTE – DCE Switch is set correctly See Section 6.9.4.
•
Verify that cable (03596) that connects the serial COM ports of the CPU to J12 of
the Motherboard is properly seated.
P/N 04316 Rev: B
TROUBLESHOOTING & REPAIR PROCEDURES
263
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