Pc-Board Removal; Digital Board; A/D Converter Board; Analog Board - Keithley 2002 Repair Manual

3.5

PC-board removal

There are three PC-boards mounted in the chassis: the digital
board, the A/D converter board, and the analog board. The
removal of these three boards is covered in this paragraph.
The display board is mounted in the front panel assembly.
The removal of the display board is covered in paragraph 3.6.
Any one of the PC-boards can be removed without having to
remove any of the other boards. Note that the A/D converter
board plugs into the analog board and can be left installed
when removing the analog board.
Before performing any of the following
procedures to remove a PC-board, remove
the case cover as explained in paragraph
3.4.1.

3.5.1 Digital board

The digital board is removed through the bottom of the chas-
sis (see drawing 2002-053). Note that the power switch push-
rod need not be removed in order to remove the digital board.
Perform the following steps to remove the digital board:
1. Unplug Cables: Turn the chassis upside-down and un-
plug the following cables from the digital board:
A. Unplug the display board ribbon cable from connec-
tor J1033.
B. Unplug the transformer cable from connector
J1032.
C. Unplug the analog board ribbon cable from connec-
tor J1027. This cable connection is located under the
power switch pushrod.
D. Unplug the fan cable from connector J1037. This
two-conductor cable connection is located at the
rear of the digital board in front of the IEEE-488
connector.
2. Unfasten PC-Board: Remove the following screws and
nuts to unfasten the digital board from the chassis:
A. At the rear panel, remove the two nuts that secure
the IEEE connector to the chassis.
B. Remove the screw that connects ground of the +5V
regulator (U629) to the chassis. The regulator is lo-
cated at the front of the digital board behind the
large electrolytic capacitor (C611).
C. Remove the four screws that secure the digital board
to the chassis. One screw is located at the rear of the
digital board in front of the bank of 12 capacitors.
Another screw is located next to the +5V regulator
NOTE
(U629). The other two screws are located near the
connector for the option slot.
3. Remove Digital Board: The board is held in place by
edge guides on each side. Slide the digital board forward
until the board edges clear the guides, and then carefully
pull the board out of the chassis.

3.5.2 A/D converter board

The A/D converter board is located under the analog board
top shield (see drawing 2002-050).
Perform the following steps to remove the A/D converter
board:
1. Remove Analog Top Shield: Position the chassis right-
side-up. The top shield is secured to the analog board by
a single screw. To remove the top shield, simply loosen
the screw, and carefully lift the shield out of the chassis.
2. Remove A/D Converter Board: The A/D converter
board is located near the front of the instrument and is
plugged into the analog board at connector J1026. The
board rests on three stand-offs. Each standoff has a re-
taining clip to hold the board securely in place. Gently
pull each retaining clip away and lift the board up until
it clears the clip. With the board clear of the three retain-
ing clips, unplug the board, and pull it out of the chassis.

3.5.3 Analog board

The analog board is removed through the top of the chassis
(see drawing 2002-051). Perform the following steps to re-
move the analog board:
1. Remove Analog Top Shield: The top shield is secured
to the analog board by a single screw. To remove the top
shield, simply loosen the screw, and carefully lift the
shield out of the chassis.
2. Remove Pushrods: Remove the pushrods for the IN-
PUTS switch and the POWER switch as follows:
A. Using suitable pliers, grasp the INPUTS pushrod
near the switch, and pull forward until it disengages
from the switch shaft. Remove the pushrod from the
chassis.
B. Turn the chassis upside-down. Grasp the rear end of
the POWER pushrod, and pull upward until it disen-
gages from the switch shaft. Remove the pushrod
from the chassis.
C. Return the chassis to the up-right position.
3. Remove Power Transformer: Remove the power trans-
former (see drawing 2002-052) as follows:
Disassembly
3-3