Removal Of The Power Supply Unit A 6 - Fluke PM3082 Service Manual

CORRECTIVE MAINTENANCE PROCEDURES
Removal of CRT controls unit A5:
- Remove the rotary knobs.
- Pull the two self-locking white plastic clamps.
- Take the unit out of the front frame.
8.5.4 Removal of the Power supply unit A6
WARNING: On the power supply unit there are many parts that carry dangerous high
voltages. Some of these voltages remain some time after disconnecting the
instrument from the mains. Therefore it is recommended to wait at least five
minutes after having disconnected the instrument from the mains, before
removing the printed circuit board, if working on the power supply under live
condition cannot be avoided, it must be done by a qualified technician who is
aware of the dangers involved.
- Disconnect the oscilloscope from the mains.
- Remove the screw that secures the unit to the chassis.
- Unplug the cables from the -2.2 kV cathode/filament (3 wires), the fan (2 wires) and the back-up
voltage (2 wires).
WARNING: The E.H.T. cable is directly connected to the E.H.T. multiplier that is present on
the power supply. When the E.H.T. cable is disconnected from the CRT, the cable
must be discharged by shorting it to the instrument's ground (e.g. the CRT
shielding).
- Unplug the +14.3 kV connector from the CRT.
- Unlock the plastic clamps (are part of the chassis) that secure the lower edges of the unit.
- Slide the unit upwards out of the instrument and unplug the mains input connector (3 thick wires).
NOTE: The power supply unit can be measured under working conditions, by using the extension
board with ordering code 5322 218 61479. On this board there is a jumper that can be
removed to switch off the EHT- converter. For safety reasons it is strongly recommended to
use this feature. Refer to chapter 8.8 for more faultfinding hints.
8.5.5 Removal of microprocessor unit A3
- Remove the screw that secures the unit to the rear panel.
- Remove the screw that secures (and grounds) the unit to the bottom chassis plate.
- Unplug the ribbon cable that leads to signal unit A1.
- If the IEEE option is installed, unplug the ribbon cable that leads to the lEEE-connector.
- Slide the unit upwards out of the instrument.
NOTE: The microprocessor unit can be measured under working conditions, by using the extension
board with ordering code 5322218 61479. On this board there is a jumper that can be
removed to switch off the EHT- converter. This feature is not used when testing the
microprocessor.
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