Troubleshooting - Agilent Technologies 8453 User Manual, Installing And Operating Manual

4 Using the Valve Unit and Valve-pump Controller
Servicing Your Valve System
Valve Position Comparator
As soon as the setpoint from the valve matches with the actual position and
the fine position has been found (position line is "1"), the run signal Run(-)
is "1".
Remote/Manual Switch, Motor Switch
If the remote/manual switch is in remote position, the run line Run(-)
connects to the motor switch and the remote LED is lit. As long as the run
signal is "0", the motor turns.
If the remote/manual switch is in manual position, the Remote LED is turned
off and the motor switch is activated by the manual advance switch through
U2. Once activated, the motor turns the encoder wheel which results in a "0"
on the position line. As soon as the next position is found (position line is "1")
the motor stops turning.
To minimize positioning errors, the motor turns in one direction only.

Troubleshooting

Most of the outputs used are open collector without pull-up resistors.
Therefore voltages on outputs can only be measured when the pull-up
resistors of the respective inputs are connected. To measure output voltages,
connect the appropriate cables and open their connectors, unless it is
specified otherwise.
Pump Does Not Respond
When trying to turn the pump in clockwise or counter clockwise direction
from the computer, the pump does not respond.
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Check if pump operates manually:
Unplug the remote cable and check if the direction switch on the front
panel of the pump works.
Check if spectrophotometer and valve-pump controller electronics work:
Observe if the channel LED on the valve-pump controller lights when pump
is activated from the software.
Agilent 8453 Dissolution Testing System Installing and Operating Manual