Smiths Kelvin Hughes Nucleus 3 5000 Series, System Handbook

Page: 366 / 510

Prep a ra tion for Fault Diagnosis
35
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 25 kW
Modulator PCB. The cover is removed by releasing the six
captive screws. Observe all safety precautions a up to 300V
is present on the modulator with power applied.
36
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 4d. To place the Electronic 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 no cables are damaged.
(3) Secure in Electronics Unit the test position on the
side of the frame with the left top and bottom
captive screws (2 only), refer to Figure 4d. 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 300V may be present
on the modulator.
37 If it is required to carry out fault diagnosis without the
300V present, set SW1 on the 25 kW Modulator PCB
to OFF. Ensure the switch is returned to the ON position
when testing is complete.
Original 7d.7 May 01
KH 2020
Chap 7d
WARNING
THIS EQUIP MENT IS NOT FITTED WITH SAFETY IN TER LOCKS AND LE THAL VOLT AGES ARE
PRES ENT WITHIN THE UNIT.
ACCESS TO THE IN TE RIOR OF THE TRANS CEIVER IS ONLY TO BE PER MITTED
FOR QUAL IFIED TECH NI CIANS.
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
these devices in their unterminated state, or modules containing these
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.