Keithley 2000 Repair Manual

Motherboard removal
Perform the following steps to remove the motherboard. This procedure assumes that the case
cover is already removed.
1. Remove the IEEE-488 and RS-232 fasteners.
The IEEE-488 and the RS-232 connectors each have two nuts that secure the connectors
to the rear panel. Remove these nuts.
2. Remove the front/rear switch rod.
At the switch, place the edge of a flat-blade screw driver in the notch on the pushrod.
Gently twist the screw driver while pulling the rod from the shaft.
3. Disconnect the front and rear input terminals.
You must disconnect these input terminal connections for both the front and rear inputs:
• INPUT HI and LO
• SENSE HI and LO
• AMPS
Remove all the connections except the front AMPS connection by pulling the wires off the
pin connectors. To remove the front panel AMPS input wire (white), first remove the AMPS fuse
holder, then use needle-nose pliers to grasp the AMP wire near fuse housing. Push the wire for-
ward and down to snap the spring out of the fuse housing. Carefully pull the spring and contact
tip out of housing.
During re-assembly, use the following table to identify input terminals:
4. Unplug cables.
C. Unplug the display board ribbon cable from connector J1014.
D. Unplug the transformer cables from connectors J1016 and J1015.
E. Unplug the scanner board ribbon cable from connector J1017.
5. Remove the fastening screw that secures the main PC board to the chassis. This screw is
located along the left side of the unit towards the rear. It also holds down U144.
During re-assembly, replace the board, and start the IEEE-488 and RS-232 connector
nuts and the mounting screw. Tighten all the fasteners once they are all in place and the
board is correctly aligned.
6. Remove the motherboard, which is held in place by edge guides on each side, by
sliding it forward until the board edges clear the guides. Carefully pull the mother-
board from the chassis.
Front wire color Rear wire color
INPUT HI
INPUT LO
SENSE HI
SENSE LO
AMPS
Red
Black
Yellow
Gray
White
White/Red
White/Black
White/Yellow
White/Gray
—
Disassembly 3-7

Keithley 2000 Specifications

General

Digits	6.5
DC Voltage Range	100 mV to 1000 V
AC Voltage Range	100 mV to 750 V
Resistance Range	100 Ω to 100 MΩ
Connectivity	IEEE-488 (GPIB)
Display Type	VFD