Ericsson MDX SERIES, Руководство по обслуживанию, Страница: 4 / 14

To Remove Surface Mounted Components
1. Grip the component with tweezers or small needle nose
pliers.
2. Alternately heat the metallized terminal ends of the chip
component with the soldering iron. If a hot-air system is used,
direct the heat to the terminals of the component. Use extreme
care with the soldering equipment to prevent damage to the
printed wire board (PWB) and the surrounding components.
3. When the solder on all terminals is liquefied, gently remove
the component. If all solder is not completely liquefied, the
use of excessive force may cause the PWB pads to separate
from the board.
4. It may be necessary to remove excess solder using a vacuum
de-soldering tool or Solderwick®. Again, use great care when
de-soldering or soldering on the printed wire boards. It may
also be necessary to remove the epoxy adhesive that was
under the chip component and any flux from the printed wire
board.
To Replace Surface Mounted Components
1. "Tin" all terminal ends on the new component and on the pads
of the PWB. Use as little solder as possible.
2. Place the component on the PWB pads, observing proper
orientation for capacitors, diodes, transistors, etc.
3. Simultaneously touch the "tinned" terminal end and the
"tinned" pad with the soldering iron. It may be necessary to
slightly press the component down on the board. Repeat this
procedure on all component terminals as necessary. Do not
apply heat for an excessive length of time and do not use
excessive solder.
With a hot-air system, apply hot air until all "tinned" areas
are melted and the component is seated in place. It may be
necessary to slightly press the component down on the board.
Touch-up the soldered connections with a standard soldering
iron if needed. Do not use excessive solder.
4. Allow the component and the board to cool and then remove
all flux from the area using alcohol or other EGE approved
flux remover.
To Replace Surface Mounted Integrated Circuits
Soldering and de-soldering techniques of the surface
mounted IC’s are similar to the procedures for the surface
mounted chip components. Use extreme care and observe static
precautions when removing or replacing the defective (or sus-
pect) IC’s. This will prevent any damage to the printed wire board
or the surrounding circuitry.
Replacement of the surface mounted IC’s is best completed
using a hot-air soldering system. See the manufacturers instruc-
tions for complete details on tip selection and other operating
instructions unique to your system.
If a hot-air system is not available, the service technician may
wish to clip the leads near the body of the defective IC and
remove it. The leads can then be removed from the PWB using
a standard soldering iron and tweezers. Install the new IC fol-
lowing the Chip Component Replacement procedures. It may not
be necessary to "tin" the IC leads before the installation process.
TROUBLESHOOTING PROCEDURES
This section should help isolate a problem to a particular
board or circuit. Block diagrams for power distribution, audio
signal flow, and logic flow are located at the back of this manual.
Refer to the appropriate LBI on the suspect board for additional
circuit information.
The Dual Format MDX 800 MHz mobile radio is divided
into 6 boards for assemblies. To aid in identifying the suspect
board, major functions for each board are given below. Refer to
the appropriate LBI on each for more details.
•
RF Board A2: Synthesizer: generates all transmit and
receive frequencies.
Receiver: provides detected audio to the
audio board.
Transmitter: includes exciter and 10 watt
PA Module.
Power control circuitry for the transmit-
ter.
Lowpass filter for the transmitter.
• PA Board A4: Power amplifier: amplifies the 10 watt
output of the RF board to 25 watts.
• Audio/Logic
Board A4: Analog filtering of the RX and TX audio
(voice, low speed data, high speed data,
and signalling tones).
RX squelch processing.
Conventional analog tone filtering and
processing.
Signal routing between the RF, audio am-
plifier, and display boards.
EEPROM for the radio personality.
The main radio microprocessor.
Accepts PTT from the microphone.
Provides DPTT to turn on the transmitter.
Provides synthesizer channel data to the
RF Board.
Generates and detects the Channel Guard
tones and data.
Generates and detects high speed and low
speed data.
Generates and detects GE-MARC busy
tones.
Generates and detects GE-MARC signal-
ling tones.
• System Board
A5 A+ switching circuitry.
Option connections.
•
Front Cap
Assembly Control Panel.
Display Board includes microprocessor
and display.
Speaker.
ERROR MESSAGES
During normal operation, the following error messages could
appear:
•
SYN LOCK - occurs when the synthesizer is unable to
lock on frequency.
•
E9 - indicates that no personality is pro-
grammed into the radio.
•
E1 - is displayed when the Group/Version
number is displayed to indicate that inva-
lid operational code is loaded into the
radios FLASH memory.
SYMPTOMS AND CHECKS
SYMPTOMS CHECKS
Blank display
on power up Check for dc voltages to J707 on the dis-
play board.
Check for A & Sw and 8 Volts on J702.
Radio will
not go into
test mode The radio must be PC programmed to en-
able the test mode. Enable it on the options
screen.
Low, distorted,
or no RX
Audio Check the receiver VOL/SQ HI output. The
problem is most likely in the RF board. If
the synthesizer load commands are not cor-
rect, the problem may be on the audio/logic
board.
If the audio is correct at VOL/SQ HI, check
the RX audio out. If improper check the
audio/logic and/or audio amplifier boards
for proper unmute commands. Proper com-
mands indicate a faulty audio/logic or
audio amplifier board.
Avoid applying heat to the body of any chip component
when using standard soldering methods. Heat should
be applied only to the metallized terminals of the
components. Hot-air systems do not damage the com-
ponents since the heat is quickly and evenly distributed
to the external surface of the component.
CAUTION
This unit contains many static sensitive components,
observe static handling precautions during any service
procedure.
CAUTION
Some chemicals may damage the internal and external
plastic and rubber parts of the radio.
CAUTION
If no conventional or GEMARC
sy ste ms are p ro gr ammed an d
Encryption Not Valid, the display will
be blank.
NOTE
LBI-38851 LBI-38851
3