CONFIDENTIAL TIBU4063-00

No procedure is currently available to direct the field on how to apply 4C-6715 Thermally Conductive Silicone Compound when removing and replacing failed 9Y-0916 Rectifier Assembly.

Note: Do Not use the primer listed as part of the 4C-6715 Rectifier Silicone Kit.

Personal injury or death can result from high voltage.

When power generation equipment must be in operation to make tests and/or adjustments, high voltage and current are present.

Improper test equipment can fail and present a high voltage shock hazard to its user.

Make sure the testing equipment is designed for and correctly operated for high voltage and current tests being made.

When servicing or repairing electric power generation equipment:

• Make sure the unit is off-line (disconnected from utility and/or other generators power service), and either locked out or tagged DO NOT OPERATE.
• Remove all fuses.
• Make sure the generator engine is stopped.
• Make sure all batteries are disconnected.
• Make sure all capacitors are discharged.

Failure to do so could result in personal injury or death. Make sure residual voltage in the rotor, stator, and the generator is discharged.

Personal injury or death can result from improper troubleshooting and repair procedures.

Qualified personnel familiar with this equipment should only perform the following troubleshooting and repair procedures.

Personal injury or death can result from high voltage.

When power generation equipment must be in operation to make tests and/or adjustments, high voltage and current are present.

Improper test equipment can fail and present a high voltage shock hazard to its user.

Make sure the testing equipment is designed for and correctly operated for high voltage and current tests being made.

Do not connect generator to a utility electrical distribution system unless it is isolated from the system. Electrical feedback into the distribution system can occur and could cause personal injury or death.

Open and secure the main distribution system switch, or if the connection is permanent, install a double throw transfer switch to prevent electrical feedback. Some generators are specifically approved by a utility to run in parallel with the distribution system and isolation may not be required. Always check with your utility as to the applicable circumstances.

Personal injury can result from improper handling of chemicals.

Make sure you use all the necessary protective equipment required to do the job.

Make sure that you read and understand all directions and hazards described on the labels and material safety data sheet of any chemical that is used.

Observe all safety precautions recommended by the chemical manufacturer for handling, storage, and disposal of chemicals.

1. Remove the 9Y-0916 Rectifier Assembly from its designated heat sink.
2. Clean the heat sink, removing all instances of old thermal conductive compound. The following solvents or equivalents are suggested to assist with thermal conductive compound removal, leaving a flat surface:

1. Toluene
2. Methyl Ethyl Ketone
3. Acetone

1. Ensure that the replacement diode base is clean from grease and dirt. Clean the replacement diode base with the prescribed thermal compound solvent.
2. From the 1.25 ounce tube of CHO-THERM 1641 silicone, squeeze a small quantity of material onto the component-mounting surface of the 9Y-0916 Rectifier Assembly.
3. Smooth the CHO-THERM 1641 silicone evenly over the entire mounting surface to a thickness of approximately 10 mil.
4. Fasten the component securely to the heat sink immediately after coating the component surface.

Note: CHO-THERM 1641 silicone cures on exposure to air. Therefore, in order to prevent curing before mounting, the component must be mounted immediately after coating.

5. Secure the cube to the heat sink. Use standard torque practices per bolt/nut using 2.37 Nm (21 lb in) to 2.60 Nm (23 lb in).
6. Make the electrical connections to the diode. Use standard torque practices per bolt/nut using 1.80 Nm (16 lb in) to 2.26 Nm (20 lb in).
7. Cure Time: Allow 16 hours for the silicon compound to cure before machine operation.

Note: If the varistor is found to be defective, the diode and the varistor most likely failed due to a transient voltage surge. The root cause is most likely the result of paralleling out of phase or a large sudden load application. If both the diode and varistor components are found defective, an application problem probably existed, not a material defects. Subsequent warranty claims could be denied.

Reference: Systems Operation, Testing and Adjusting, Troubleshooting, SENR3985, "SR4 Generators with VR3 or VR4 Voltage Regulators"

Reference: Systems Operation, Testing and Adjusting, Troubleshooting, SENR5359, "SR4B Generator"

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