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4
Service Information
4-1
WARNING
The information in this section is in-
tended only for qualified service person-
nel. Some of the procedures may expose
you to hazardous voltages that could re-
sult in personal injury or death. Do not
attempt to perform these procedures
unless you are qualified to do so.
4.1
Introduction
This section contains information necessary to service the
Model 7020 card and is arranged as follows:
• Handling and cleaning: Discusses handling precautions
and methods to clean the card should it become
contaminated.
• Functionality test: Provides a test procedure to
determine if an input or output channel is functioning
properly.
• Special handling of static-sensitive Devices: Reviews
precautions necessary when handling static-sensitive
devices.
• Principles of operation: Briefly discusses circuit
operation.
• Troubleshooting: Presents some troubleshooting tips
for the Model 7020.
4.2
Handling and cleaning
Care should be taken when handling or servicing the card to
prevent possible contamination. The following precautions
should be taken when servicing the card.
Handle the card only by the edges and shields. Do not touch
any board surfaces or components not associated with the re-
pair. Do not touch areas adjacent to electrical contacts.
Should it become necessary to use solder on the circuit
board, use an OA-based (organic activated) flux. Remove the
flux from the work areas when the repair has been complet-
ed. Use pure water along with clean cotton swabs or a clean
soft brush to remove the flux. Take care not to spread the flu
to other areas of the circuit board. Once the flux has been re-
moved, swab only the repaired area with methanol, then
blow dry the board with dry nitrogen gas.
4.3
Channel functionality test
An input or output channel can be tested without the use of
test equipment.
1. As shown in Figure 4-1, connect the suspect input or
output channel to an output or input channel that is
known to be functioning properly. Note that for the out-
put channel, the pull-up resistor must be installed, and
the internal 5.3V supply must be used.
2. From the front panel of the mainframe, turn on (close)
the output channel. Verify that the display indicates that
the output channel is on (closed). Keep in mind that the
output is low when the channel is turned on.