Digital Circuitry Checks - Keithley 2015 Service Manual

4-20 Troubleshooting

Digital circuitry checks

Digital circuit problems can be checked out using Table 4-4.
Table 4-4

Digital circuitry checks

Step Item/component
1 Power-on test
2 U152 pin 14
3 U152 pin 28
4 U135 pin 48
5 U135, lines A1-A23
6 U135, lines D1-D15
7 U135 pin 44
8 U159 pin 13
9 U159 pin 14
10 U158 pins 34-42
11 U158 pins 26-31
12 U158 pin 24
13 U158 pin 25
14 U135 pin 84
15 U135 pin 91
16 U135 pin 90
17 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