Additional Instructions - Garmin GTX 330 System Maintenance Manual

NOTE
Ensure that the voltmeter and power supply probes do not touch, so as not to induce
contact resistance.
2. Touch negative lead of power supply to each of the test points listed while performing Step 3. At
each point, configure the power supply to produce 1 amp before measuring voltage. (Use an
ammeter to ensure current is within 1 amp ±100 milliamp at each point).
3. Set the voltmeter to measure millivolts and null the reading. Measure the voltage from the engine
grounding bracket (step 1) to each of the following points and record the voltage. (Perform Step 2 at
each point to ensure that 1 amp ±100 milliamp is present before measuring.)
•
Top metal case of GTX 330 #1: __________ millivolts (if installed)
•
Top metal case of GTX 330 #2: __________ millivolts (if installed)
•
GTX 33 #1 top: __________ millivolts (if installed)
•
GTX 33 #2 top: __________ millivolts (if installed)
•
Upper Transponder Antenna: __________ millivolts (if installed)
•
Lower Transponder Antenna: __________ millivolts (if installed)
Ensure that at each test point, no more than 5 millivolts (5 mΩ) are present. In this case, voltage is
equivalent to resistance (Ω), given that precisely 1 amp reference current is present.
TIP: If 1 amp reference current cannot be maintained, note the difference between the attainable current
and 1 amp reference current. Calculate the percentage difference and apply this to the voltage reading to
obtain the equivalent resistance. Example: If the measured current is 1.2 amps, (20% high from the target
1 amp current), then the allowable voltage measurement would be 20% high, 5 millivolts would now be 6
millivolts.
4.7

ADDITIONAL INSTRUCTIONS

Electrical load information for the GTX is provided below. Appendix A of this document contains details
specific to the load changes for the installation.
Characteristic
Maximum Full TSO Reply Rate
Maximum Quiescent
GTX 330/33 with ADS-B Out
Maintenance Manual with ICA
The document reference is online, please check the correspondence between the online documentation and the printed version.
Table 5. GTX Electrical Load
14 Volt Current Draw
3.1 A
1.1 A
4-6
Specification
28 Volt Current Draw
1.6 A
0.85 A
190-00734-11
Rev. 1