ARMY TM 5-6775-238-14
MARINE CORPS TM 08839A-14/1
a. Signal Processor Unit. The signal processor
unit (also referred to as SPU) chassis consists of an
open type welded frame with a heat exchanger, hous-
ed in an instrument case. All connectors and operating
controls are located on the front panel. Input and out-
put air ducts are also located on the front panel.
b. Punched Tape Reader. The punched tape reader
(also referred to as tape reader) is housed in an instru-
ment case. The operating control (or controls) is
located on the front panel along with the tape spooler,
time totalizing meter, two fuses, and a connector.
c. Buffer Unit. The buffer unit is contained in an
aluminum housing with a sealed cover. Two connec-
tors are installed in the housing. Left and right sup-
ports are attached to the housing.
d. Transit Cases. Three transit cases are provided
for transporting the PADS test set or for storage
during long periods of nonuse. These cases are water-
tight and dusttight and contain a pressure relief
valve.
1-9. Differences Between Models. There is only one
model of Position and Azimuth Determining System
Test Set AN/USM-427. However, there are two
models of the tape reader used in this test set. The
earlier model tape reader part no. is 877406-1. The
later model tape reader part no. is 877406-2.
Whenever the tape reader is discussed and there are
differences between the two tape readers, the part
numbers will be included in the discussion as
applicable.
1-10. System Application. The PADS test set may
be utilized to check out the computer, inertial
measurement unit, or control and display unit. When
an inertial measurement unit (IMU) or control and
display unit (CDU) is connected to the PADS test set
for checkout, an operational computer must also be
connected. In addition, an operational power supply
must be connected to the computer. The PADS test
set is also capable of loading the computer memory
with the supplied IMU alignment tape. In addition,
provisions are made for using a teletypewriter with
the PADS test set during testing and troubleshooting
of the PADS equipment.
1-11. Tabulated Data. PADS test set performance
characteristics are given in table 1-1.
1-12. Items Comprising an Operable Equipment.
Items comprising the operable PADS test set are
illustrated in figure 1-1 and listed in tables 1-2, 1-3, and
1-4.
Legend for Figure 1-1
1.
2.
3.
3.1
4.
5.
6.
7.
8.
9.
10.
Signal Processor Unit
TS-3617/USM-427
Signal Processor Unit Case
CY-7563/USM-427
Punched Tape Reader
RP-239/USM-427 (Part No.
877406-1)
Punched Tape Reader
RP-239/USM-427 (Part No.
877406-2)
Punched Tape Reader Case
CY-7562/USM-427
Buffer Unit CV-3404/USM-427
Test Set Accessories Case
CY-7609/USM-427
Cable Assembly, Power Electrical,
W201
Cable Assembly, Special Purpose,
Electrical, W203
Cable Assembly, Special Purpose,
Electrical, W204
Cable Assembly, Special Purpose,
Electrical, W205
1-2
Change 4
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
Cable Assembly, Special Purpose,
Electrical, W212
Cable Assembly, Special Purpose,
Electrical, W209
Cable Assembly, Special Purpose,
Electrical, W210
Card Extractors
Self-Test Tape
Take-Up Reels (six reels)
Diagnostic Tape (two reels)
Operational Tape
Card Extender, Tape Reader (used
on Part No. 877406-1)
Maintenance Manual: Army TM
5-6675-238-14 or Marine Corps TM
08839A-14/1
RPSTL: Army TM 5-6775-238-24P
or Marine Corps TM 08839A-24P/2
Shorting Plug
Solid State Program Tape (three reels)
Cable Assembly, Special Purpose,
Electrical, W211