Digital Circuitry Checks - Keithley 2000 Repair Manual

2-12 Troubleshooting

Digital circuitry checks

Digital circuit problems can be checked out using Table 2-4. See "Principles of Operation"
for digital circuit.
Table 2-4

Digital circuitry checks

Step
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Item/component
Power-on test
U152 pin 16
U152 pin 32
U135 pin 48
U135, lines A1 thru A23
U135, lines D1 thru D15
U135 pin 44
U159 pin 13
U159 pin 14
U158 pins 34-42
U158 pins 26-31
U158 pin 24
U158 pin 25
U135 pin 84
U135 pin 91
U135 pin 90
U135 pin 89
Required condition
RAM OK, ROM OK.
Digital common.
+5V
Low on power-up, then goes
high.
Check for stuck bits.
Check for stuck bits.
14.7456MHz
Pulse train during RS-232 I/O.
Pulse train during RS-232 I/O.
Pulse train during IEEE-488 I/O.
Pulses during IEEE-488 I/O.
Low with remote enabled.
Low during interface clear.
Pulse train.
Pulse train.
Pulse train.
Pulse train.
Remarks
Verify that RAM and
ROM are functional.
All signals referenced
to digital common.
Digital logic supply.
MPU RESET line.
MPU address bus.
MPU data bus.
MPU clock.
RS-232 RX line.
RS-232 TX line.
IEEE-488 data bus.
IEEE-488 command
lines.
IEEE-488 REN line.
IEEE-488 IFC line.
ADRXB
ADTX
ADCLK
ADTS