home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
World of Ham Radio 1997
/
WOHR97_AmSoft_(1997-02-01).iso
/
mods
/
kenwood
/
asb_text
/
asb0981.txt
< prev
next >
Wrap
Text File
|
1997-02-01
|
3KB
|
76 lines
==============================================================================
K E N W O O D
>>> A M A T E U R R A D I O S E R V I C E B U L L E T I N <<<
==============================================================================
Kenwood Service Centers
Kenwood Service Corporation Kenwood Service Center, East
2201 East Dominguez Street 829 Lynnhaven Parkway, Suite 130
Long Beach, California 90801 Virginia Beach, Virginia 23452
Telephone 1-310-639-5300 Telephone 1-804-340-1702
==============================================================================
BULLETIN # 981
MODEL: TH-77A
SUBJECT: MEMORY LOSS WITH LOW BATTERY PACK
Some of the TH-77A handhelds in serial number range S/N 206XXXXX
intermittently lose memory when the NiCad battery pack becomes discharged.
The following modification will correct this condition. TH-77A transceivers
in serial number range S/N 207XXXXX and above will incorporate a change
in the microprocessor to prevent this condition.
This modification requires the ability to desolder a surface mounted
micro-miniature chip resistor from a flex PC board. If you do not remove
micro-miniature chip resistors from flex PC boards on a regular basis,
DO NOT attempt this modification.
Be sure to remove the battery terminal plate in step 2. If the battery
terminal plate is left on the transceiver (only the top 2 screws removed)
the flex cable for the CTCSS unit can be damaged.
REQUIRED PART:
33K OHM CHIP RESISTOR RK73GB1J333J
MODIFICATION PROCEDURE:
1. Disconnect the battery and antenna.
2. Remove the 4 screws from the battery terminal plate and then remove
the plate. FIGURE 1
3. Remove three case screws from the transceiver. FIGURE 1
4. Carefully open the transceiver. Be careful not to break the flex cable
that connects the front panel Control board to the body of the transceiver.
5. Locate chip resistor R301 on the Control board inside the front panel
of the transceiver. FIGURE 2
6. Check for a solder bridge between the foil trace connected to the bottom
of R301 and the foil trace below it. If present, carefully desolder the
solder bridge.
7. Remove chip resistor R301.
RECOMMENDED METHOD: Use a hot air jet system to melt the solder on both
sides of the resistor. When the solder is molten, remove the chip resistor
with a pair of tweezers.
OPTIONAL METHOD: Use a wedge shaped soldering iron tip to melt the solder
on both sides of the resistor at one time. As the solder melts, the chip
resistor will lift from the board and stick to the soldering tip.
Do not attempt to pry the chip resistor from the board. FIGURE 3
8. Install a 33K ohm chip resistor in place of R301. Do not re-connect the
solder bridge removed in step 6.
9. Assemble the transceiver. Make sure the CTCSS board is positioned
correctly so the flex cable is not stressed. Do not force the radio
together.
Time required to perform this modification is 1 hr or less.