R&E » Keithley 2001 repair

Defective system trigger bus.
System trigger inputs are normally pulled up to 5V through the protection diodes and
5.1kohm resistors (CR611-CR616, R648-R650 and R655-R657). The Model 2001 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 veriÞed 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 operation of the trigger bus.

Suspected:
ASIC, FETs, diodes and 5.1kohm resistors.