Hitachi 51SWX20B, Service Manual

Page: 9 / 189

9
DP27/27D
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 1.6K
Ω resistor, 0 = 0 Ω
(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
Fiat-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.
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.
NOTE:
These components are affixed with glue. Be careful not to break or damage any foil under the
component or at the pins of the ICs when removing. Usually applying heat to the component for a short
time while twisting with tweezers will break the component loose.
Chip Components
TYPE
GRADE
C
B
E
SOLDER
CAPS
TRANSISTOR CAPACITOR
1ST DIGIT
2ND DIGIT
MULTIPLIER
= 1600 = 1.6K
ANODES
MH DIODE RESISTOR
SOLDER CAPS
COMMON CATHODE
De-Solder
Braid
Soldering
Iron
Soldering
Iron
Soldering
Iron
Soldering
Iron
Soldering
Iron
Soldering
Iron
De-Solder
Braid
Flat-IC
Bridge
Solder
De-Solder
Braid
Iron
Wire
Pull
Awl
Polarity Symbol
5. Solder all pins to the soldering pads using a fine
tipped soldering iron.
SERVICING PRECATIONS