Display Board - Keithley 2701 Service Manual

Section 4: Troubleshooting
AC power is applied to the AC power module receptacle. Power is routed through the line fuse and
line voltage selection switch of the power module to the power transformer. The power transformer
has a total of four secondary windings for the various supplies.
AC voltage for the display filaments is taken from a power transformer secondary at F1 and F2, then
routed to the display board.
Each DC supply uses a rectifier and a capacitive filter, and many supplies use an IC regulator. The
next table summarizes rectifier, filter, and regulator circuits for the various DC supplies.
Supply
+5 VD
+3.3 VD
+2.5 VD
+1.8 VD
+37 V
+15 V
-15 V
+5 V, +5 VRL, +5 V2
+18 V
-18 V

Display board

Display board components are shown in the digital circuitry block diagram in the next figure.
4-6
Model 2701 Ethernet-Based DMM / Data Acquisition System Service Manual
Rectifier Filter
CR104 C156, C273, C274, C281
- C66
- C205
- C214
CR115, CR117 C104
CR102 C148
CR102 C131
CR103 C146
CR102 C148
CR102 C131
Regulator
U144
U18
U25
U19
U101
U125
U119
U124
-
-
2701-902-01 Rev. B / December 2018