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Unit Operation Checks
4. MAIN POWER ASSY
Outline
The MAIN POWER ASSY uses switching power supplies to convert the supply voltage (100
to 240VAC) into the various supply voltages: DC POWER-A (±24V), IG CTRL-A (+5V), and
IS CTRL-A (+5V). It incorporates a PCB that provides ON/OFF control of the rotary pumps
and turbo molecular pumps.
Operation Check Method
If an abnormality occurs, follow the procedure below to check the operation of the MAIN
POWER ASSY to efficiently diagnose the problem.
Caution
A voltage of 100 to 240VAC is supplied to the MAIN POWER ASSY. To avoid electric
shocks or damage to the assembly, touch only the points instructed.
1. Checking the supply voltage
First, check that the power switch is in the OFF position. Disconnect the MAIN POWER
ASSY cable connectors (Connectors c to j in the diagram) from the boards supplied or
from MAIN POWER. Turn ON the power switch and measure the voltage at each
connector on the power line, as follows:
TMP1: Measure the voltage at Pin 1 of Connector c in the block diagram, relative to Pin 2.
(normal range: +22.7 to +25.3VDC)
TMP2: Measure the voltage at Pin 1 of Connector d in the block diagram, relative to Pin 2.
(normal range: +22.7 to +25.3VDC)
IS CTRL-A: Measure the voltage at Pin 3 of Connector e in the block diagram, relative to
Pin 1.
(normal range: +4.8 to +5.3VDC)
IG CTRL-A: Measure the voltage at Pin 3 of Connector f in the block diagram, relative to
Pin 1.
(normal range: +4.8 to +5.3VDC)
DC POWER-A: Measure the voltage at Pin 1 of Connector g in the block diagram, relative
to Pin 3.
(normal range: +22.7 to +25.3VDC)
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