Is Service Bulletin (SB) 8 installed in the KTR-953 (Receiver Exciter)?
Are SBs 9, 10, 11 and 13 installed in the KAC-952 (Antenna Coupler)?
What is the distance (> or < 3 feet) between the mounting location of the KAC-952 and the KTR-953?
What type of antenna (shunt or long wire) is being used on your aircraft?
The following is a list and description of relevant SBs:
KTR-953
SB 8: To reduce transmit distortion encountered when the KTR-953 is mounted in a different location (> 3 feet) than the KAC-952.
KAC-952
SB 9: To improve common mode rejection encountered when the KAC-952 and the KTR-953 are installed in separate locations.
SB 10: To reduce transmitter distortion when the KAC-952 is mounted more that three feet from the KTR-953.
SB 11: To prevent the failure of the power amplifier driver and final transistors.
SB 13: Mod 13 improves the tuning reliability of some shunt antennas.
Troubleshooting
KTR-953 SB 8 must be installed simultaneously as KAC-952 SBs 9 and 10 to achieve proper system operation and prevent possible unit failure. If SB 9 and 10 are not installed on the KAC-952, SB8 may cause damage to the power transistors that can cost in excess of $2400.
If the SBs are installed in the KAC-952 but not in the KTR-953, the system may not function properly by either not tuning or being intermittent in performance.
We highly recommend you comply with SB 11 due to its description and the increasing cost of the power transistors.
If you are using a shunt style antenna, Service Bulletin 13 in the KAC-952 should definitely be installed. In our experience the installation of SB 13 will not affect the performance when used with a long wire antenna.
Some other KHF-950 notes:
Remember the SB’s that are applicable to the Falcon 900 only
Bridging amp coaxes must be crossed
The coax at the receiver/exciter can be unplugged. Insert a 10 or 20 foot test lead as a antenna
The right MLG door full open prox detector failed, shorted to ground through the case. This tells the main gear it is clear to retract when in fact the door is mid travel.