Chapter 6. REPAIR INSTRUCTIONS

TM 9-4931-378-13&P

CHAPTER 6

REPAIR INSTRUCTIONS

Section I. GENERAL INSTRUCTIONS

Static Pressure Signal

The test set is functionally

6-1. General Description.

Differential Pressure Signal

divided into five sections; power, AADS test, LAI test, EPU

AADS Reference Signal

test, and TS monitor. Figure 6-1 is a block diagram of the

Fore-Aft TAS Signal

test set and figure FO-1 is the schematic diagram of the

Lateral TAS Signal

front panel/chassis wired assembly.

Fore-Aft IAS Signal

Power Section. The power section requires 115

Lateral IAS Signal

Vat, 50, 60 or 400 Hz and +28 Vdc input power. The 115

LAI +15 Vdc

Vac is used by power supplies PS1 and PS2 to provide +5

LAI -15 Vdc

Vdc and 15 Vdc respectively. Power supply PS1 provides

ADS FAIL Discrete Signal

operating power to the test set circuits, test set decimal dis-

ADS NO GO Discrete Signal

play and panel lighting power to the LAI under test; PS2

Serial Data

provides operating power to the test set circuits, LAI and

Data Ready

AADS LRU's under test. The +28 Vdc source provides

e. TS Monitor Section. The TS monitor section pro-

operating power to the test set indicator lamps and to the

vides test set monitor functions of the 115 Vac and +28

EPU under test. Switches and test points are provided to

Vdc input power, the +5 Vdc, +10 Vdc, -10 Vdc voltages

monitor voltage and current supplied to the LRU's under

and the following test set outputs may be test point moni-

test.

tored:

The AADS test section

b. AADS

Test

Section.

SIN α

routes test set generated 15 Vdc and simulated AADS Ref-

Cos α

erence signal to the AADS under test. The AADS Test

SIN

Switch (S16) and the associated test points provide for

Cos

monitoring the four resolver outputs, the air temperature

sensor output, and the continuity/resistance of the anti-

icing heater,

Radar Altitude

The LAI test section routes

LAI Test Section.

Reference Oscillator

15 Vdc operating power to the LAI under test, simulates

f. Display Driver Circuit Card Assembly 1A1. T h e

fore-aft IAS, lateral IAS, and ADS FAIL signals. The PNL

serial data applied to this circuit card assembly (CCA) is

LIGHTS switch (S19) provides +5 Vdc to test the panel

converted into an eight-bit parallel data word. This data

lights of the LAI under test.

word is applied to eight lamp drivers and three binary-to-

d. EPU Test Section, The EPU test section routes

seven segment decoder/drivers. The lamp drivers supply

+28 Vdc and the following simulated signals to the EPU

binary data bits B0 through B7 to drive front paneI indica-

tors DS8 through DS1 respectively. Meanwhile, the binary-

under test:

Four resolver AADS angle signals

to-seven decoders convert the eight-bit data word to three

sets of signals. These signals drive three digit display DS12

Air Temperature

on the test set front panel. Setting SELF TEST switch S5

Radar Altitude

on the front panel to SELF TEST enables the self test input

Radar Altimeter Reliability

to CCA 1A1. The data registers are loaded with logic 1`s,

LAI FAIL discrete

turning on twelve lamp drivers and all of the seven segment

CPU TEST discrete

decoder drivers.

Data Transmit Request

g. Clock and Comparator CCA 1A2. Clock circuits

Data Clock

on this CCA generate the data clock and data transmit

The EPU test section monitors the following test points or

request waveforms illustrated in figure 5-13. DATA WD SEL

outputs of the EPU under test to isolate EPU faults:

switch S8 on the front panel selects inputs for the comparator

EPU +5 Vdc

on this CGA. The comparator generates the proper number

EPU -5 Vdc

of clock pulses to load the selected word from the serial

EPU +12 Vdc

data into CCA 1A1. The clock pulses shut off when the

AADS +15 Vdc

selected word is loaded into CGA 1A1. Also, CCA 1A2 has

AADS -15 Vdc

6-1