Hitachi 50VF820 Service Manual page 7

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.
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 capaci-
tor 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 identi-
cal 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 gen-
eral 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
Chip Components
TYPE
C
GRADE
B
TRANSISTOR
E
COMMON CATHODE
ANODES
SOLDER CAPS
MH DIODE
SERVICING PRECAUTIONS
SOLDER
CAPS
CAPACITOR
1ST DIGIT
2ND DIGIT
MULTIPLIER
= 1600 = 1.6K
RESISTOR
7
How to Replace Flat-lC
—Required Tools—
• Soldering iron
• De-solder braids
1. Remove the solder from all of the pins of a Flat-lC by
using a de-solder braid.
Flat-IC
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.
Soldering
Pull
Iron
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.
Solder
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.
Bridge
Solder
LC58/LC58E
• iron wire or small awl
• Magnifier
De-Solder
Braid
Soldering
Iron
Iron
Wire
Awl
Soldering
Iron
Soldering
Iron
De-Solder
Braid
Flat-IC
Polarity Symbol
Soldering
Iron
De-Solder
Braid
Soldering
Iron