RF SECTION, TROUBLESHOOTING.

TM 11-4920-296-14&P

3-15. RF SECTION, TROUBLESHOOTING.

via front-panel connectors, no internal wires

If problems are detected from the general

need to be disconnected during this opera-

trouble analysis tests (figure 3-1 and table 3-2)

tion.

which indicate faults within the rf module Al or

3-21. Whenever disassembling the test set

its subassemblies, proceed as follows:

or its components, refer to the illustrations

1. Turn off power and remove the retain-

of Section 6 (IPB), for location of mounting

ing screws from the. rf module. Lift the

screws, and placement of the components.

module from its chassis connector, leaving

Normal soldering and maintenance. tech-

the three rf cables attached to their jacks at

niques are employed for disassembly of the

the side of the module. Rotate the rf mod-

equipment. During replacement of any part,

ule to pemit access to its printed circuit

tag all wires removed, and check that they

board assembly. Make a detailed inspec-

are reinstalled to their correct points.

tion of the connections from the three rf

Dress leads as nearly as possible to their

modules to the printed wiring board assem-

original positions, when replacing parts.

bly. If any are broken, repair and reinstall

3-22. REMOVAL OF DIGITAL PRINTED

the Al module. If this does not correct the

CIRCUIT CARDS. The four replaceable

test set malfunction, remove and reconnect

printed circuit-card modules of the test set

the module to its chassis connector via an

are mounted in the card cage behind the

extender cable assembly.

front-panel assembly. Removal of any of

2. Reapply power to the test set and per-

these cards consists of unfastening the card-

form the tests of table 3-3 and figure 3-2.

retaining bar and pulling the specific card

Refer to the rf module A1 PCB track wiring

from its mounting connector (by operating

diagram (figure 3-8) for identification of

the card insert/extraction levers).

test points and locations.

3-23. REMOVAL OF RF MODULE AND

3-16. When performing the trouble analysis

SUBMODULES. To remove the rf module

tests for the rf module Al, use stands rd rf

from its normal mounting position on the

practices of connection (shortest possible

chassis, first disconnect the rf cables con-

l e a d s , etc.). Some disconnection of leads

nected to its jacks. Then loosen the two

may be necessary during those tests; care

captivated hold-down screws, and lift the

should be taken to prevent damage to com-

module out of its chassis connector. Access

ponents or PCB tracks. Always remove

to the submodules of the rf module requires

power to the test set prior to unsoldering/

removal of its protective cover. Individual

soldering connections. For continuity

submodules can then be removed by discon-

checks, insure that power to the test set is

nection of their wires, and removal of their

off. When the trouble analysis tests for the

mounting screws. Exercise care when re-

rf module Al have been completed, check

moving or replacing submodules, to avoid

that all connetions have been reconnected

damaging connector contacts, or other com-

(if they were disconnected).

ponents in the process of replacing one sub-

module.

3-17. BULK ITEMS CONSUMABLE LIST.

3-18. The only items that are consumable

3-24. REMOVAL OF CHASSIS ASSEMBLY

bulk items are solder and rags used inunsol-

FROM FRONT PANEL ASSEMBLY. For

dering and soldering of leads to components to

access to the front-panel controls, and to

make parameter measurements of table 3-3.

the power supply components of the test set, it

is necessary to separate the front panel and the

3-19. DISASSEMBLY.

chassis assemblies. This is accomplished by

3-20. The test set is conventionally con-

removing the screws holding the chassis to

structed, and can be disassembled into its

the rear of the front-panel assembly. Normal

component modules, chassis, and panel

unsoldering techniques are used to discon-

using normal maintenance tools. Separa-

nect wires from any part being replaced.

tion of front panel from the case is accom-

CLEANING.

3-25.

plished by unfastening the four screws at

the front panel, and pulling the front-panel/

3-26. No special cleaning procedures are

chassis assembly out of the case. Since all

required for the test set.

connections to the test set circuits are made

3-3