Common J.E.T MT-101x Mach Trim Computer Squawks

January 2023

Duncan Aviation Avionics Instruments Shop has repaired more than 350 J.E.T MT-101X Mach Trim Computers in the last 10 years. Our autopilot technicians average more than 20 years of experience on these units.

Through our experience, we have seen many of these units become inoperative for a variety of reasons. The following are the most common squawks and what is causing them.

1. Trim switch becomes inop: Trim diodes go bad
2. Power supply inop: Designed with power supply resistors too close to the PC board causing heat-related problems to the components and the board
3. Power supply inop: Old style tantalum capacitors have reached their end life
4. Holes drilled through the case and PC boards: Occurs during installation in the aircraft.
5. Lost adjustment potentiometer locking nuts
6. Older units not fused 

Here Are The Solutions:

1. Replace trim diodes currently in stock at Duncan Aviation.
2. Installation of Service Bulletin SB501-1132-19 replaces and lifts the power supply resistors off the board, reducing heat stress to components and board, giving a longer life to the power supply. Parts currently in stock at Duncan Aviation.
3. Installation of SB501-1132-18 replaces old style power supply capacitors with new aluminum electrolytic improving the life span of the power supply. Parts currently in stock at Duncan Aviation.
4. At Duncan Aviation, we know where to look for these squawks and will repair them properly.
5. We have a solution for adjustment potentiometers that are no longer available and the hardware associated with them.
6. Installation of SB501-1132-2 will introduce a fuse into the power supply circuit, reducing catastrophic failures to the unit and the aircraft. Parts currently in stock at Duncan Aviation.