Keithley 2750 Service Manual

4-10 Troubleshooting Model 2750 Multimeter/Switch System Service Manual
Figure 4-3
Analog circuitry block diagram
Scanner
Inputs
BUFCOM
Slot 1
INPUT
HI
SENSE
LO
Scanner Outputs
DCV
OHMS
DCV/100
Current
Shunts
K103, R158,
R205, R338
AC Switching
&
Gain
½K102, U102, U103, U105,
U112, U118, U111, U110, U117
SSP*
Q101, Q102
DCV
Divider
R117, Q109,
Q114, Q136
Ohms I-Source
Q119, Q123,
Q124, Q125, Q126,
½K102, U123, U133
DCV & Ohms
Switching
K101, Q104,
Q108, Q113
X1
Buffer
U113
Digital
Circuitry
(See Figure 4-2)
ADC
U165
A/D
MUX &
Gain
U129, U132
U163, U166
SENSE
HI
ACV,
FREQ
AMPS
DCA
ACA
Slot
Control
* Solid State Protection
Front Terminals
Scanner Outputs
K101
SSP* CR105, Q159
SSP*
Q122, Q135
SSP*
Q150, Q151
Front Terminals
Scanner Outputs
Front Terminals
Scanner Outputs
Front Terminals
Scanner Outputs
Scanner
Inputs
Slot 5
S101
S101
S101
S101
Dry Circuit
Stability
Clamp
C152, C164,
K104
Dry Circuit
Voltage Clamps
U162, U206
Low Ohms
Sensing
Q106
Temp.
Sensor
(CJC)
Protection
DS101,
102
A/D MUX
Overload
Protection
Q103, 107, 117,
CR101, 113,
U128,140, 143
VR110, 111
Temp. Sensors

Keithley 2750 Specifications

General

Interface	GPIB, RS-232, Ethernet
Switching Speed	Up to 500 channels/second
Maximum Voltage	300V
Operating Temperature	0°C to 50°C
Measurement Functions	DCV, ACV, DCI, ACI, 2-wire Resistance, 4-wire Resistance, Frequency, Temperature
Resolution	6.5 digits
Current	1A
Maximum Current	1A