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Troubleshooting Procedures
6–22
1780R-Series Service Manual
WARNING. Dangerous potentials exist on the LV Power Supply board. Use care
when troubleshooting to prevent personal injury. Read the instructions given in
the Troubleshooting portion of this section.
Power Supply
The 1780R-Series power supply presents special troubleshooting problems, if a
fault occurs. Besides having a sizeable area where dangerous potentials can be
contacted, the type of circuitry employed can not be troubleshot by conventional
means.
WARNING. Do not attempt to troubleshoot the 1780R-Series power supply
without reading these instructions.
Circuitry in this power supply, for troubleshooting purposes, can be divided into
two categories: Control and Primary. The first area to troubleshoot is the control
circuits, which requires an external DC supply. Once the control circuitry has
been eliminated as the source of the problem, then move on to the primary.
Carefully follow instructions regarding placement of ground leads and discon-
necting of loads to avoid personal hazards and potential circuit damage.
WARNING. Do not attempt to work on the power supply primary circuitry without
using an isolation transformer.
Several pieces of equipment, that may not be found on a typical service bench,
are required to service this instrument’s low voltage power supply. These are
items that are in addition to the equipment called out in the Performance
Verification and Adjustment Procedures in this manual. A DC power supply is
required to power up the low voltage control circuits (Base Drive, Controller,
Starter, etc.). An isolation transformer is required to work on the power supply
primary circuits, which are located on both the Low Voltage Power Supply
circuit board (Assembly A1) and the Fuse circuit board (Assembly A17).
Troubleshooting
Equipment