Service manual

Repair and Maintenance Guidelines

This section provides guidelines for handling the relay multiplexers

including:

• ESD precautions

• Soldering printed circuit boards

• Post-repair safety checks

ESD Precautions Electrostatic discharge (ESD) may damage static sensitive devices in the

multiplexers. This damage can range from slight parameter degradation to

catastrophic failure. When handling multiplexer assemblies, observe the

following guidelines to avoid damaging multiplexer components:

• Always use a static-free work station with a pad of conductive rubber

or similar material when handling multiplexer components.

• If a device requires soldering, be sure the assembly is placed on a

pad of conductive material. Also, be sure that you, the pad, and the

soldering iron tip are grounded to the assembly.

Soldering Printed

Circuit Boards

Some of the components on the etched circuit boards of the multiplexer

modules have plated through-holes that provide a solder path to both sides

of the insulating material. Soldering can be done from either side of the

board with equally good results. When soldering to any circuit board, keep

in mind the following guidelines:

• Avoid unnecessary component unsoldering and soldering. Excessive

replacement can result in damage to the circuit board, adjacent

components, or both.

• Do not use a high power soldering iron on etched circuit boards, as

excessive heat may lift a conductor or damage the board.

• Use a suction device or wooden toothpick to remove solder from

component mounting holes. When using a suction device, be sure

that the equipment is properly grounded.

Post-Repair Safety

Checks

After making repairs to the multiplexer, inspect the multiplexer for any

signs of abnormal internally generated heat, such as discolored printed

circuit boards or components, damaged insulation, or evidence of arcing.

Determine and correct the cause of the condition. Then perform the

functional tests as described in Chapter 2, "Verification Tests," to verify that

the multiplexer is functional.

Chapter 4 Service 59