4-20
4.29 MICROPROCESSOR CONTROLLER
NOTE
For manual override operation of the
microprocessor, refer to Table 4-7.
CAUTION
When doing any arc welding on the unit or
container, disconnect all connectors from
controller and remove ground lead going to I/O
board to prevent any damage due to electrostatic
discharge.
a. Handling of Microprocessor Controllers
Here is a list of guidelines that should be followed
when handling a microprocessor controller. These steps
should be implemented when replacing the controller,
when doing
any
arc welding on the unit, or
when service to
the refrigeration unit requires handling and removal of the
controller.
1. Obtain a grounding wrist strap and a static
dissipation mat. The wrist strap, when properly
grounded, will dissipate any potential built up on the
body. The dissipation mat will provide a static free work
surface to place and/or service the microprocessor
controller. Note: Use a dissipation mat such as the 3M
8501 Static Protective Field Service Kit or equivalent. For
information write: Static Control Systems Division/3m,
P.O. Box 2963, Austin, Texas 78769-2963.
2. Disconnect power to the unit.
3. Attach the ground or clip end of the wrist strap to
any exposed metal area on the refrigeration unit frame
(bolts, screws, etc.).
4. Carefully remove the microprocessor controller.
Do not touch any of the electrical components if possible.
Place the controller on the static mat. If arc welding is to
be performed on the unit, it is not necessary to remove
controller. Simply disconnect all connectors
from
controller and remove ground lead going to I/O board.
5. At this point, if you are servicing the
refrigeration unit, you are free to remove the ground
strap from your wrist and complete your work.
5a. Upon completion of your service work put the
wrist strap back on, and re-install the controller into the
refrigeration unit.
6. If you are replacing the controller, do not
remove the wrist strap. Remove the new microprocessor
controller from its packaging and install it on the
refrigeration unit. Place the old controller into the same
packaging that accompanied the new controller.
Make
sure that you package it in the exact same manner.
NOTE
This packaging has been designed to protect the
controller from both physical and electrostatic
discharge damage during storage and transit.
b. Removing and Installing Microprocessor
Control Box
1. Remove two screws (item 5, Figure 4-26) and
swing control panel (item 6) down.
2. Remove three screws and loosen three other
screws to remove cover (item 3).
3. Disconnect all plug connectors and move wiring
out of the way.
4. Remove two screws (item 1)
and slide
microprocessor control box (item 4) and two spacers
(item 2) to the left and out.
NOTE
There are two spacers in the right hand side of
the electrical box. DO NOT LOOSEN these
spacers as they are factory positioned.
5. Install microprocessor control box by reversing
the above steps.
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