Chapter 6. FUNCTIONING OF EQUIPMENT

ARMY TM 5-6675-309-14

MARINE CORPS TM 08840A-14/1

CHAPTER 6

FUNCTIONING OF EQUIPMENT

6-1. General. This section describes the function of the

-28V power is also divided down to -10V for internal

PSSTS and interconnecting cable assemblies. A PSTS

use in the PSTs. A +28V, 8 amp fuse, a -28V, 1/2

amp fuse, and a +10V, 1/4 amp fuse protect these

functional block diagram description is given, followed

by detailed descriptions of each function.

circuits.

f. Switching input power to the UUT is shown in

6-2. PSTS Function. The PSTS is capable of testing the

figure 6-3. The 0 to +40V, 20 amp power is applied to

PADS PS and PADS COMP PS functions when used

the UUT only when the MODE switch is in the NO

with a digital voltmeter, multimeter, and oscilloscope.

LOAD position. Switching is accomplished by relays

A simplified functional block diagram is shown in figure

RE. The 0 to +40V power is also used for testing the

6-1, and a detailed functional block diagram is shown in

PS battery charging circuitry (figure 6-3).

figure FO-1.

g. Power to the PS is applied whenever the INPUT

a. Power to the unit under test (referred to herein

POWER UUT circuit breaker is closed. Power to the

as UUT) is routed through the PSTS and controlled by

COMP PS requires, in addition to INPUT POWER

PSTS power control circuitry. Power inputs to the

UUT circuit breaker being closed, that relays RF be

PSTS are +28V, 40 amps, and 0 to +40V, 20 amps.

closed by selecting the ON position of the COMP PS

These voltages may also be provided to the UUT.

switch.

b. Mode and load select circuits are controlled by

PSTS front panel switches to cause the UUT to accept

h. The 28V source (figure FO-1) also powers the

selected input signals or to drive selected loads. Opera-

REFERENCE switch which selects reference voltages

tion of the UUT is then monitored at the test jacks on

between +8V and -5V as required by the UUT. The

the PSTS front panel or at front panel indicators. Loads

reference voltage is fed through a voltage limit circuit

are selectable as no-load, full-load, or overload values.

for fail-safe operation and is then sent to the UUT

These loads are applied in accordance with specified

through connector J2 to the COMP PS and to the PS.

loading requirements of each UUT output voltage.

i. Primary control of PSTS circuitry is by the

c. A multimeter is used to measure the various

MODE and FUNCTION switches. The MODE switch

voltages or currents. An oscilloscope is used to measure

is active only when interconnecting cables for the PS,

timing signals and waveforms. Measured values are

or for the COMP PS, are correctly connected. Correct-

compared to values specified in the direct support and

ness of interconnection is determined by a UUT detect

general support maintenance manual (TM 5-6675-308-

circuit and by UUT on monitoring circuits in the PSTS

34 or TM 08837A-34/2) to determine if the UUT is

(see figure FO-1). If the UUT is properly connected, and

operating properly.

has been turned on, the corresponding PS ON/COMP

PS ON indicator will light. The MODE switch is active

d. The PSTS contains built-in test equipment

when interconnecting cabling is correct, whether or not

(BITE) circuitry which is used to assure the operator

the UUT has been turned on. When the MODE switch

that the PSTS is operating correctly. Malfunctions of

is placeed in +RECT LOAD position, -RECT LOAD

the PSTS are detected by BITE and a fault is isolated to

position, or FULL LOAD position, the FUNCTION

a small group of replaceable components or circuit

switch will be activated so that the proper resistive

cards.

loads will be applied to the UUT by relays RD. The

e. PSTS power control circuitry is shown in detail

load applied is dependent upon the function selected at

in figure 6-2. Both the INPUT POWER PSTS circuit

the FUNCTION switch.

breaker and POWER SUPPLY TEST SET ON switch-

j. When the MODE switch is placed in the OVER-

indicator must be in the closed (or ON) position to

LOAD or the OVERVOLT position, and the UUT is

activate the 28 VDC power circuits. Only the TIME

turned on, the 2-second timer will be activated by

HOURS meter and fan is activated by the INPUT

pressing the INITIATE switch. If the MODE switch is

P O W E R PSTS circuit breaker alone. When the

POWER SUPPLY TEST SET ON switch-indicator is

in the OVERLOAD position, the proper resistive over-

load will then be applied to the UUT through relays

pressed to on, it closes relays RG (figure 6-2). Closing

relays RG causes the indicator of POWER SUPPLY

RD. If the MODE switch is in the OVERVOLT posi-

TEST SET ON switch-indicator to light and to supply

tion, the proper overvoltage will be applied to the UUT

from an overvoltage generator through relays RC.

the -28V and +10V converters PS1 and PS2. The

6-1