Keithley 2750, Service Manual

Page: 108 / 179

4-22 Troubleshooting Model 2750 Multimeter/Switch System Service Manual
Table 4-14 through Table 4-19 can be used to trace the analog signal through the A/D mul-
tiplexer (U163) to the final amplifier stage. These tables show the MUX lines (S3, S4, S6,
S7) that are selected for measurement during the SIGNAL phase of the multiplexing
cycle. Also included are switching states of analog switches (U129) that set up the gain for
the final amplifier stage (U166).
Table 4-14
DCV signal multiplexing and gain
Range
Signal
(U163)
U129
Pin 1
U129
Pin 8
U129
Pin 9
Gain
(U166)
100mV
1V
10V
100V
1000V
S4
S4
S4
S4
S4 OFF
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
OFF
OFF
OFF

100

10

1

10

1
Table 4-15
ACV and ACA signal multiplexing and gain
Range
Signal
(U163)
U129
Pin 1
U129
Pin 8
U129
Pin 9
Gain
(U166)
All S3 ON OFF OFF

1
Table 4-16
DCA signal multiplexing and gain
Range
Signal
(U163)
U129
Pin 1
U129
Pin 8
U129
Pin 9
Gain
(U166)
20mA
100mA
1A
3A
S6
S6
S6
S6 OFF
OFF
OFF
OFF OFF
OFF
OFF
ON
ON
ON
ON
OFF

100

100

100

10