Model 1707B Service
Table 8-4. Troubleshooting Low Voltage Power Supply
Indications Procedures, Checks, Probable Causes
Power lamp on Check all low voltage outputs. If OK, go to table
Scale lamps on 8-5. If not, continue.
Power lamp off Check following on schematic 21 :
Scale lamps on 1. ?50V outputs (fuses).
2. Rectifiers and filters.
Check low voltage converter and regulator
(schematic 20)
Power lamp on Check following on schematic 20:
Scale lamp off 1. Scale lamps.
2. Scale lamp driver.
Power lamp off Refer to note 1. Check following on sche-
Scale lamps off matic 19:
1. Ac line fuse AIFI.
2. POWER MODE switch.
3. Dc line fuse FI.
4. Voltage Limiter and battery Regulator.
5. Line Rectifier.
Note 1
At normal ac line voltage, there should be
about 33 Vdc at POWER MODE switch.
Dc line fuse F1 Refer to note 2. Disconnect power cord.
open. Remove LV converter assy A3A2 (schematic
20). Replace fuse and reconnect power cord.
1. Fuse does not open. Check LV converter
assy A3A2.
2. Fuse opens. Check low voltage converter
protection circuits.
Note 2
If dc input or+l5V regulated input to low volt-
age converter protection circuits is 20% or
more, high circuits will activate and open dc line
fuse FI. If inputs OK, suspect problem in low
voltage converter protection circuits.
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ACEC
HEWLETT-PACKARD
