Triggers Tests - Keithley 2002 Repair Manual

2.11.4

Triggers tests

Test 105.1 through 105.6 — System trigger bus
Type
Fault message
Description
Drawing reference
Components
Test 105.7 — External Trigger/Meter Complete
Type
Fault message
Description
Drawing reference
Components
Triggers are controlled by the 5064 ASIC (U618). This component has seven trigger outputs
(STO1-STO7) and eight trigger inputs (STI1-STI8). Lines STI1-STI6 and STO1-STO6 are used
to control the system trigger bus, line STO7 is used for Meter Complete, and line STI7 is used
for External Trigger. STI8 is connected to the Group Execute Trigger signal (GET) of the 9914
IEEE-488 bus controller (U622).
Pass/Fail
Trig link channel <n> open
System trigger inputs are normally pulled up to 5V through the protection diodes and 5.1k Ω re-
sistors (CR611-CR616, R648-R650 and R655-R657). The Model 2002 can generate a trigger on
any of the six trigger bus inputs by turning on the appropriate FET (Q602-Q607). These FETs
are controlled by system trigger outputs (STO1-STO6) of the 5064 ASIC (U618).
In test 105.1, STI1 is set up as the trigger input. The trigger 1 FET (Q606) is then turned on and
off through STO1, and it is verified that this trips the trigger circuitry in the ASIC. This test is
then repeated for trigger 2 through 6 for tests 105.2 through 105.6. Success indicates proper op-
eration of the trigger bus.
Digital Board; 2002-140
ASIC (U618), FETs (Q602-Q607), diodes (CR611-CR616), and 5.1k Ω components resistors
(R648-R650, R655-R657).
Pass/Fail
Shorted VMC/EXT trigger
This test is similar to System Trigger tests 105.1 through 105.6 except that there is no internal
connection between External Trigger and Meter Complete. Consequently, the meaning of a fail-
ure is reversed from that of the previous trigger tests. A failure is registered if a trigger does oc-
cur. A failure indicates that a short exists between External Trigger and Meter Complete.
An alternate way to test these triggers is to externally connect a BNC cable from External Trig-
ger to Meter Complete. When test 105.7 is run, the short should cause the test to fail. If it does
not, a problem in the signal path exists.
Digital Board; 2002-140
External Trigger/Meter Complete signal paths.
(<n> = 1 to 6)
Troubleshooting
2-21