T150/150G/T400/400G Course Computers
16
Type 150/150G/400/400G Course Computers Service Manual 83156-1
Type 150/400 Course Computers
Current Sense Resistors
Using a DVM set to Ohms, measure the resistance of resistors R167 and R133.
These are 10m
Ω
resistors. Unless the DVM is extremely sensitive, it will be difficult to
measure this accurately. For the purposes of this test follow the steps below to determine
whether they are intact:
1. Set the DVM to measure Ohms.
2. Touch the two probes together and make a note of the resistance measured. This
should be close to 0
3. Measure across the resistor R167
4. The measured value should be virtually the same as that measured in step 2
5. Repeat for resistor R133
Check Rate Gyro Connection
The plug is designed to fit one way into the socket. Ensure that the keyed side of the plug
faces the outermost side of the PCB when inserted. There are matching slots in the socket
to accommodate this.
Red
Yellow
Black
D6101-1
Relay Visual Checks
(The relay (RL1) on the Course Computer PCB can carry up to 40A, but if for any reason,
it does not close, this will cause DX to fail.)
•
Check for dirt or flux residue around the relay contacts
•
Check for signs of blackening or burnt out track around diode D4 and resistor R323
FET SIL Pad
The SIL pad is a thermally conductive but electrically isolative strip of material, which sits
between the metal tabs of the power devices and the metal heatsink. The material ensures
that there is good thermal conductivity between the power devices and the metal heatsink,
but also provides a high level of electrical isolation between the tabs and the heatsink. If
