Service manual

6-1
April 2001
Part No. 001-9800-203
SERVICING
6.1 GENERAL
CAUTION
LTR-Net™ models (see Sections 1.3 and 1.4) may
automatically transmit during normal operation and
at power off to send registration and de-registration
messages. Therefore, to prevent accidental damage to
a signal generator attached to these models, be sure to
use an adequate isolation pad.
6.1.1 PERIODIC CHECKS
This transceiver should be placed on a periodic
maintenance schedule to ensure that it continues to
operate properly. Important checks are receiver sensi-
tivity and transmitter frequency, deviation, and power
output. Performance tests are located in Sections 7.4
and 7.5.
6.1.2 SCHEMATIC DIAGRAMS AND
COMPONENT LAYOUTS
Schematic diagrams and component layouts for
the various PC boards used in this transceiver are
located in the back of this manual. Included are RF
and audio/logic board and interconnect schematics.
The component layouts permit easy location of
components and measurement points. For the RF and
audio/logic boards, a component locator guide and
grid around the boards are provided to aid in locating
components. All boards in this transceiver have
components mounted on one side only. Therefore,
most servicing can be done without removing the
board from the chassis.
6.1.3 REPLACEMENT PARTS
A replacement parts list for this transceiver is
located in Section 8. The main listing includes the RF
board and chassis parts and another listing includes
the audio/logic board parts. Parts are listed alphanu-
merically according to designator. For information on
ordering parts, refer to Section 1.9. An exploded view
of the transceiver is also included at the end of Section
8 to show the various mechanical parts.
6.1.4 CONFIGURING TRANSCEIVER FOR
TESTING
This transceiver has a test mode which can be
selected to perform testing. The test mode is described
in Section 3.11, and it permits the transceiver to be
operated manually. To select the test mode, turn power
on with the following option switch(es) pressed. The
test mode is especially useful when only LTR opera-
tion is programmed because the receiver and trans-
mitter are then inhibited until a handshake is
completed with a repeater.
Low Tier Models
- Top (A/D) switch
High Tier Models
- Top two switches (to right of
display)
If adjustments must be made to the various audio
and data levels, the programming setup and special
Radio Tune software are required as described in
Section 1.2.7. The procedure for aligning the trans-
ceiver is located in Section 7.
6.2 SURFACE MOUNTED DEVICES (SMDs)
6.2.1 SERVICING TECHNIQUES
Most of the components used in this transceiver
are the surface mounted type. Since these components
and the circuit traces on which they are mounted are
very small in size, special care must be used when
they are replaced. Multi-leaded components such as
integrated circuits must usually be removed using a
heat gun or some other type of heat source that heats
the entire device. Take care so that nearby components
are not damaged. Surface mounted components should
not be reused since they may be damaged by the
unsoldering process.
6.2.2 IDENTIFYING SMD RESISTORS
The value of resistors is indicated by a number
printed on the resistor. A three-digit number is used to
identify ±5% and ±10% resistors, and a four-digit
number is used to identify ±1% resistors. Refer to the
following information.
SECTION 6 SERVICING