IC Remove/Replacement
IC Remove/Replacement
Some chassis circuit boards have slotted holes (oblong) through
Some chassis circuit boards have slotted holes (oblong) through
which the IC leads are inserted and then
which the IC leads are inserted and then
bent at against the cir-
bent at against the cir-
cuit foil. When holes are the slotted type, the following technique
cuit foil. When holes are the slotted type, the following technique
should be used to remove and replace
should be used to remove and replace
the IC. When working with
the IC. When working with
boards using the familiar round hole, use
boards using the familiar round hole, use
the standard technique
the standard technique
as outlined in paragraphs 5 and 6 above.
as outlined in paragraphs 5 and 6 above.
Removal
Removal
1. Desolder and straighten each IC lead in
1. Desolder and straighten each IC lead in
one operation by
one operation by
gently prying up on the lead
gently prying up on the lead
with the soldering iron tip as the
with the soldering iron tip as the
solder melts.
solder melts.
2. Draw away the melted solder with an anti-static suction-type
2. Draw away the melted solder with an anti-static suction-type
solder removal device (or with solder braid) before
solder removal device (or with solder braid) before
removing
removing
the IC.
the IC.
Replacement
Replacement
1. Carefully insert the replacement IC in the circuit board.
1. Carefully insert the replacement IC in the circuit board.
2. Carefully bend each IC lead against the
2. Carefully bend each IC lead against the
circuit foil pad and
circuit foil pad and
solder it.
solder it.
3. Clean the soldered areas with a
3. Clean the soldered areas with a
small wire-bristle brush.
small wire-bristle brush.
(It is not necessary to reapply acrylic coating to the areas).
(It is not necessary to reapply acrylic coating to the areas).
"Small-Signal" Discrete Transistor
"Small-Signal" Discrete Transistor
Removal/Replacement
Removal/Replacement
1. Remove the defective transistor by clipping its leads as close
1. Remove the defective transistor by clipping its leads as close
as possible to the
as possible to the
component body.
component body.
2. Bend into a "U" shape the
2. Bend into a "U" shape the
end of each of three leads
end of each of three leads
remain-
remain-
ing on the circuit board.
ing on the circuit board.
3. Bend into a "U" shape the
3. Bend into a "U" shape the
replacement transistor leads.
replacement transistor leads.
4. Connect the replacement transistor leads to the corresponding
4. Connect the replacement transistor leads to the corresponding
leads extending from the circuit board and crimp the
leads extending from the circuit board and crimp the
"U" with
"U" with
long nose pliers to insure metal to
long nose pliers to insure metal to
metal contact then solder
metal contact then solder
each connection.
each connection.
3. Solder the connections.
3. Solder the connections.
CAUTION: Maintain original spacing between the replaced
CAUTION: Maintain original spacing between the replaced
component and adjacent components and the circuit board to
component and adjacent components and the circuit board to
prevent excessive component temperatures.
prevent excessive component temperatures.
Circuit Board Foil Repair
Circuit Board Foil Repair
Excessive heat applied to the copper foil of
Excessive heat applied to the copper foil of
any printed circuit
any printed circuit
board will weaken the adhesive that bonds the
board will weaken the adhesive that bonds the
foil to the circuit
foil to the circuit
board causing the foil to separate from or
board causing the foil to separate from or
"lift-off" the board. The
"lift-off" the board. The
following guidelines and procedures should be followed when-
following guidelines and procedures should be followed when-
ever this condition is encountered.
ever this condition is encountered.
At IC Con
At IC Con
nections
nections
T
T
o repair a
o repair a
defective copper pattern at IC
defective copper pattern at IC
connections use the
connections use the
following procedure to install a jumper wire on
following procedure to install a jumper wire on
the copper pattern
the copper pattern
side of the circuit board. (Use this technique only on
side of the circuit board. (Use this technique only on
IC connec-
IC connec-
tions).
tions).
1. Carefully remove the damaged copper pattern with a
1. Carefully remove the damaged copper pattern with a
sharp
sharp
knife. (Remove only as much copper as absolutely necessary).
knife. (Remove only as much copper as absolutely necessary).
2. carefully scratch away the solder resist and acrylic coating (if
2. carefully scratch away the solder resist and acrylic coating (if
used) from the end of the
used) from the end of the
remaining copper pattern.
remaining copper pattern.
3. Bend a small "U" in one end of a small gauge jumper wire and
3. Bend a small "U" in one end of a small gauge jumper wire and
carefully crimp it around the IC pin. Solder
carefully crimp it around the IC pin. Solder
the IC connection.
the IC connection.
4. Route the jumper wire along the
4. Route the jumper wire along the
path of the out-away copper
path of the out-away copper
pattern and let it overlap the
pattern and let it overlap the
previously scraped end of the
previously scraped end of the
good copper pattern. Solder the overlapped area
good copper pattern. Solder the overlapped area
and clip off
and clip off
any excess jumper wire.
any excess jumper wire.
At Other
At Other
Connect
Connect
ions
ions
Use the following technique to repair the defective copper pattern
Use the following technique to repair the defective copper pattern
at connections other than IC Pins. This technique involves the
at connections other than IC Pins. This technique involves the
installation of a jumper wire on the
installation of a jumper wire on the
component side of the circuit
component side of the circuit
board.
board.
Summary of Contents for 42LB550A
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Page 49: ...Appendix Exchange PSU LED driver No Light Dim Light Dim Light Dim Light No picture Sound Ok ...