Digital Board Removal; A/D Converter Board Removal; Analog Board Removal - Keithley 6517 Service Manual

front panel assembly. The removal of the display board is
covered in paragraph 6.6.
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
6.4.

6.5.1 Digital board removal

The digital board is removed through the bottom of the chas-
sis (see drawing 6517-053). 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 J1029. This cable connection is located under the
power switch pushrod.
d. Unplug the interlock cable from connector J1030.
This four-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 items to
unfasten the digital board from the chassis:
a. At the rear panel, remove the nuts that secure the
IEEE-488 and RS-232 connectors to the chassis.
b. Remove the clip that secures regulators U629 and
U642 to the chassis. This clip is located adjacent to
the pushrod near the front panel.
c. Remove the three screws that secure the digital
board to the chassis. One screw is located at the rear
of the digital board near the interlock connector, and
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.
NOTE

6.5.2 A/D converter board removal

The A/D converter board is located under the A/D Board
shield on the analog board (see drawing 6517A-050).
Perform the following steps to remove the A/D converter
board:
1. Remove A/D board shield: Position the chassis right-
side-up. The A/D board shield is secured to the analog
board by two screws. To remove the shield, simply
remove the screws and carefully lift the shield away
from the A/D converter board.
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, one of which has a retaining
clip to hold the board securely in place. Gently pull the
retaining clip away and lift the board up until it clears
the clip. With the board clear of the retaining clip,
unplug the board and pull it out of the chassis.

6.5.3 Analog board removal

The analog board is removed through the top of the chassis
(see drawing 6517-053). Perform the following steps to
remove 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 pushrod: Remove the pushrod for the POWER
switch as follows:
a. 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.
b. Return the chassis to the up-right position.
3. Remove power transformer: Remove the power trans-
former (see drawing 6517A-054) as follows:
a. Disconnect the transformer ground. A kep nut is
used to connect this green ground wire to a threaded
stud on the chassis.
b. Unplug the transformer. There are five plugs for the
transformer. Four are located on the analog board at
connectors J1024, J1025, J1027, and J1028, and the
fifth is located on the digital board at connector
J1032. Turn the chassis upside-down to gain access
to the plug on the digital board. When finished,
return the chassis to the up-right position.
Disassembly
6-3