Digital Circuitry Checks; Table 4-4 Digital Circuitry Checks - Keithley 2750 Service Manual

Model 2750 Multimeter/Switch System Service Manual

Digital circuitry checks

Digital circuit problems can be checked using
Table 4-4
Digital circuitry checks
Step Item/Component
1 Power-on test
2 U152, pin 16
3 U171, pin 16
4 U194, pin 1
5 U171, pin 4
6 U135, pin 68
7 U135, lines A0-A20
8 U135, lines D0-D15
9 U135, pin 60
10 U159, pin 13
11 U159, pin 14
U158, pins 34-42
12
13 U158, pins 26-31
14 U158, pin 24
15 U158, pin 25
16 U135, pin 48
17 U135, pin 76
18 U135, pin 77
19 U135, pin 74
Required Condition
RAM OK, ROM OK.
Digital common.
+5V (+5VD supply).
+5V (+5VB supply).
+3V
Low on power-up, then goes high.
Check for stuck bits.
Check for stuck bits.
32.758kHz
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.
Troubleshooting
Table 4-4.
Remarks
Verify that RAM and ROM are functional.
All signals referenced to digital common.
Digital logic supply.
Battery backed memory supply.
Battery voltage (BT100).
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
4-15