Disassembly; Fanfiltermaintenance; Special Handling Of Static Sensitive Devices - Keithley 224 Instruction Manual

5.4 DISASSEMBLY
If it should become necessary to disassemble the Model 224
use the following procedure. Also, refer to Figure 5-1.
1. Remove the top cover as follows:
WARNING
Turn the instrument off, disconnect all
other equipment from the Model 224 and
disconnect the line cord before removing
the top cover.
A. Remove the two retaining screws located at the rear of
the instrument.
B. Grasping the top cover at the rear, carefully lift it off of
the instrument.
C. When installing the top cover, make sure that the three
tabs that are located at the front of the cover engage in
the front panel assembly.
2. Remove the IEEE-488 interface board (Model 2243).
A. Unplug the ribbon cable (J/P10041 at the mother
board.
B. Remove the phillips head retaining screw located near
J1004 on the interface board.
C. Remove the two retaining bolts that secure the inter-
face board and IEEE-488 standard connector to the rear
panel.
D. Lift the interface out of the mainframe.
E. To install the Model 2243 reverse the above procedure.
3. Remove the analog board shield.
A.
B.
C.
D.
Remove the four slot head screws that secure the shield
to the analog board.
Lift the shield and the four slot head screws away from
the analog board.
Remove the two screws that secure the analog board
bottom shield to the analog board.
Remove the analog board bottom shield.
NOTE
The circuitry located beneath the analog board
shields is extremely sensitive. Do not touch any
of the range resistors or input cable.
4. Remove the analog board.
A. Remove the phillips head screw located directly behind
the two power transistors.
B. Unplug the ribbon cable (J/P10031 from the analog
board.
C. Remove the bottom shield of the analog board by
removing the two phillips head screws that secure the
shield to the board.
NOTE
Do not remove the output cable.
5. Place the analog board along side of the Model 224.
6. Remove the mother board from the case.
A. Remove the four plastic standoffs.
B. Remove the two phillips screws that secure the mother
board to the case. They are located at the rear of the
mother board, one by the fan and the other is by the
line voltage selector switch S102.
C. Remove the two phillips head screws that secure the
case to the rearspanel.
D. Unplug the display ribbon cable (J/P1002) from the
mother board.
E. Grasp the mother board and the rear panel
simultaneously. Lift the mother board and the rear
panel up and toward the rear of the instrument. Then
lift the mother board and rear panel out of the case.
8. Remove the display board.
A. Remove the two phillips head screws that secure the
display board to the front panel.
B. Remove the front panel buttons.
C. Lift the display board out of the case.
9. For reassembly, perform steps l-8 in reverse order.
NOTE
When installing connectors J/P1004, J/P1003
and J/ PI002 be sure to align pin one of the con-
nector to pin one of the cable.
5.5 FAN FILTER MAINTENANCE
The internal temperature generated by the Model ?24
necessitates the forced air cooling provided by the fan. The
fan has an air filter which keeps the instrument relatively free
of dust and dirt. Dust and dirt collect on the filter and impede
the air flow through the instrument. Lack of
air flow will
cause overheating. Therefore, the filter must be kept clean in
order for the Model 224 to maintain optimum performance.
To clean the filter:
1. Remove the filter from the fan.
2. Use compressed air to remove the dust and dirt from the
filter. If the filter is excessively dirty wash it in mild soap
and water and dry it with compressed air.
3. Reinstall the filter.
5.6 SPECIAL HANDLING OF STATIC SENSITIVE
DEVICES
MOS devices are designed to function at high impedance
levels. Normal static charge can destroy these devices. Table
5-4 lists all the static sensitive devices of the Model 224.
Steps 1-7 provide instruction on how to avoid damaging
these devices.
1. Devices should be handled and transported in protective
containers, antistatic tubes or conductive foam.
2. Use a properly grounded workbench and grounding
wriststrap.
5-2