Hitachi UT42V702/D8MW, Service Manual

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D8MW
TABLE OF CONTENTS
7
Leadless Chip Components
(surface mount)
Chip components must be replaced with identical chips
due to critical foil track spacing. There are no holes in
the board to mount standard transistors or diodes. Some
chip capacitor or resistor board solder pads may have
holes through the board, however the hole diameter
limits standard resistor replacement to 1/8 watt. Standard
capacitors may also be limited for the same reason. It is
recommended that identical chip components be used.
Chip resistors have a three digit numerical resistance
code -1st and 2nd significant digits and a multiplier.
Example: 162 = 1600 or 1.6KΩ resistor, 0 = 0Ω
(jumper).
Chip capacitors generally do not have the value indicated
on the capacitor. The color of the component indicates the
general range of the capacitance.
Chip transistors are identified by a two letter code. The
first letter indicates the type and the second letter, the
grade of transistor.
Chip diodes have a two letter identification code as per the
code chart and are a dual diode pack with either common
anode or common cathode. Check the parts list for correct
diode number.
Component Removal
1. Use solder wick to remove solder from component
end caps or terminals.
2. Without pulling up, carefully twist the component
with tweezers to break the adhesive.
3. Do not reuse removed leadless or chip
components since they are subject to stress
fracture during removal .
Chip Component Installation
1. Put a small amount of solder on the board
soldering pads.
2. Hold the chip component against the soldering
pads with tweezers or with a miniature alligator
clip and apply heat to the pad area with a 30 watt
iron until solder flows. Do not apply heat for more
than 3 seconds
How to Replace Flat-lC
—Required Tools—
• Soldering iron • iron wire or small awl
• De-solder braids • Magnifier
1. Remove the solder from all of the pins of a Flat-lC
by using a de-solder braid.
2. Put the iron wire under the pins of the Flat-lC and pull
it in the direction indicated while heating the pins using a
soldering iron. A small awl can be used instead of the iron
wire.
3. Remove the solder from all of the pads of the Flat-lC by
using a de-solder braid.
4. Position the new Flat-lC in place (apply the pins of the
Flat-lC to the soldering pads where the pins need to be
soldered). Properly determine the positions of the soldering
pads and pins by correctly aligning the polarity symbol.
5. Solder all pins to the soldering pads using a fine tipped
soldering iron.
6. Check with a magnifier for solder bridge between the pins
or for dry joint between pins and soldering pads. To remove
a solder bridge, use a de-solder braid as shown in the figure
below.
MH DIODE RESISTOR
Chip Components
TYPE
GRADE
C
B
E
SOLDER
CAPS
TRANSISTOR CAPACITOR
1ST DIGIT
2ND DIGIT
MULTIPLIER
= 1600 = 1.6K
ANODES
SOLDER CAPS
COMMON CATHODE
De-Solder
Braid
Soldering
Iron
Soldering
Iron
Soldering
Iron
Iron
Wire
Pull
Awl
Soldering
Iron
De-Solder
Braid
Flat-IC
Polarity Symbol
Soldering
Iron
Solder
Bridge
Solder
De-Solder
Braid
Soldering
Iron