Chapter 3. DIRECT SUPPORT MAINTENANCE INSTRUCTIONS

TM 11-6125-261-30

CHAPTER 3

DIRECT SUPPORT MAINTENANCE INSTRUCTIONS

Section I. GENERAL

NOTE

coded to the test points (Al through A20) shown on the

The maintenance allocation chart for the in-

block diagram figure FO-1. Also shown is the reference

verter is located in TM 11-1520-236-20.

designator of the component or terminal where the

measurement is taken.

3-1. Voltage and Resistance Measurements

3-2. Wire List

a. Table 3-1 shows the voltage and resistance measure-

ments that can be expected in the inverter. Voltages were

a. The inverter uses two wire harnesses and one wire

measured with no load on the output.

assembly. in addition the A1 module uses nine short

jumpers of No. 18 bus wire and 18 short jumpers of No. 16

WARNING

black insulated wire.

Relatively low voltage but high current is

b. The 277B2023 wire hamess is composed of No. 16, 20,

present in the inverter.

22 and 24 gauge wire for control signals. The 277B3300 wire

harness is composed of No. 16 guage wire for high current

b. Resistance measurements are shown in the forward

signal connections to the main transformer. The 277C1340

and back mode. The resistance on the top indicates the

wire assembly is composed of No. 14 gauge red insulted wire

forward resistance and the value on the bottom indicates

for the M28 V dc power bus. All insulted wire is in accord-

back resistance.

ance with MIL-W-16878/1 or MIL-W-16878/4A. The crimp

c. Table 3-2 is across reference between the components

lugs are AMP Products Corp., Valley Forge, PA. 19482,

for all three phases that have the same function.

FSCM00779 or equivalent.

d. Figure 3-1, sheets 1 through 6, contain all the significant

c. Table 3-3 contains a to-from wire list for the inverter.

waveforms required for maintenance. Each waveform is

Table 3-1. Voltage end Resistance Measurements

TEST CONDITIONS

A. Voltage measurements

+28.0 V dc

1. Input voltage

Adjust to 115.5 V ac f V sc 400 Hz No Load.

2. Output voltage

Voltages are references to ground.

3. Voltage listing

NOTE

The A-number in the voltage columns indicate the test point reference number of the waveform. Refer to figure 3-1.

. Resistance measurements.

1. Unit OFF and disconrectcd from the +28 V dc source

2. All resistance measurements are ±5%.

3. Remove associated Z elements indicated by *.

4. Resistance measurements were made with a standard 20,000 ohm/volt VOM on the Xl scale.

5. The transistor type is noted below the referenced designation. All transistors and diodes are silicon types

6. This table shows the transistors, for OA only. Refer to table 3-2 for equivalent ±B and ±C transistors.

7. Top number in Resistance column indicates forward resistance, bottom, backwards resistance.

3-1

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