Keithley 2182, Service Manual, Page: 55 / 120

4-8 Troubleshooting
Figure 4-3
Simplified schematic of analog circuitry
PROTECTION
CH2_HI
CH 2
Q671
+
-
BOOTSTRAP
AMP
U638
ACAL
U643
7V_REF 1V_REF
0.1V_REF
LO
Q663
PA
TH A
Q61
1, 612
Q613, 614
PA
TH B
+V -V
Q624
FLIP_UPPER_B
U61
1
FLIP_UPPER_A
Q622(P
A
TH A)
Q623(P
A
TH B)
PROTECTION
Q627, 630
+ -
U614
TP651
X1 X5 X100
U645
R648 R600
R 6 4 1
R 7 1 7
CH1 HI
CH1
Q666, 667
PROTECTION
Q664(1V
-10mV)
Q665(10V)
20K
Q672
9.9M 100K Q673, 674
CH1
CH1 LO
+
-
+ -
U601
PBS
NBS
PBB_SLO
NBS_SLO
U600
BUFFER
LN_COM
CH2_LO
R693
PROTECTION
ON FRONT P
ANEL
TEMP
SENSOR
Q670
Q638
APPROX 0.23V
MUL
TIPLEXER
LN_COM
DIV_COM
7V_REF 1V_REF
0.1V_REF
LO
U626
+
-
U630
X1 X10 X100
U 6 3 2
R664 R665 R666
GAIN AMP
TP652
T
O
A/D
CONVER
TER
LOW NOISE PREAMPLIFIER
Q661, Q662
Q633, Q634
VR61
1, VR612