Smiths Kelvin Hughes Nucleus 3 5000 Series, System Handbook

Page: 388 / 510

PREP A RA TION FOR FAULT DI AG NO SIS
38
To access the units inside the transceiver it is
necessary to remove the front cover of the transceiver.
This allows access to all the units except the 25kW
Modulator PCB. The cover is removed by releasing the six
captive screws. Observe all safety precautions as up to 300V
is present on the modulator with power applied.
39
To access the indicators and the test points on the
25kW Modulator PCB, it is necessary to place the
Electronics Unit (CTX-A370) in the test position, refer to
Figure 6e. To place the Electronics Unit in the test position,
proceed as follows:
(1) Remove all power supplies to the transceiver.
(2) Release the six captive screws securing the
electronic assembly in position and carefully
remove, ensuring that no cables are damaged.
(3) Secure the Electronics Unit in the test position on
the side of the frame, with the left top and bottom
captive screws (2 only), refer to Figure 6e. It is now
possible to access the LED indicators and the test
points on both sides of the unit.
(4) Restore power to the transceiver, observing all
safety procedures, as up to 300VV may be
present on the modulator.
40
If it is required to implement fault diagnosis without
300V present, set switch SW1 on the 25kW Modulator
PCB to OFF. Ensure that the switch is returned to the ON
position when testing is complete.
Original 7d.7 May 01
KH 2020
Chap 7d
WARNING
THIS EQUIPMENT IS NOT FITTED WITH SAFETY INTERLOCKS AND LETHAL VOLTAGES ARE
PRESENT WITHIN THE UNIT.
ACCESS TO THE INTERIOR OF THE TRANSCEIVER IS ONLY TO BE PERMITTED FOR QUALIFIED
TECHNICIANS.
CAUTIONS
(1) Handling of Electrostatic Sensitive Semiconductor Devices
Semiconductor devices used in the equipment are liable to damage due to static voltage.
Observe the following precautions when handling static sensitive devices in their un-terminated state,
or when handling modules containing such devices.
Persons removing modules from an equipment using these devices should be earthed
by a wrist strap and a resistor.
Soldering irons used during repair operations must be low voltage types with earth tips
and isolated from the mains voltage by a double insulated transformer.
Outer clothing worn must be unable to generate static voltages.
Printed Circuit Boards (PCBs) fitted with these devices must be stored
and transported in anti-static bags.
Fit new devices in a special handling area.
For detailed information, refer to British Standard BS 5783 or other equivalent standard.
(2) Use non-magnetic tools when working near the magnetron.