RCA SelectaVision VideoDisc SJT 400 Basic Service Data page 4

1983 5ЈТ 400 SERVICING PRECAUTIONS
Replacement
1. Сагеюйу insert the replacement IC in the circuit board
2. Carefully bend each ІС lead against the circuit foil pad and
solder it
3. Clean the soldered areas with a small wire-bristle brush. (It is
not necessary to reapply acrylic coating to the areas.)
"Small-Signal" Discrete Transistor Removal/Replacement
1. Remove the defective transistor by clipping its leads as close
as possible to the component body
2. Bend into a "U" shape the end of each of three leads remain-
ing on the circuit board
3. Bend into a "U" shape the replacement transistor leads.
4. Connect the replacement transistor leads to the correspond-
ing leads extending from the circuit board and crimp the "U"
with long nose pliers to insure metal to metal contact, then
solder each connection
Remove the heatsink mounting screw (if so equipped)
Insert new transistor in circuit board
Solder each transistor lead, and clip off excess lead.
Фа ы о м
Replace heatsink
Diode Removal/Replacement
1. Remove defective diode by clipping its leads as close as pos-
sible to diode body
2. Bend the two remaining leads perpendicularly to the circuit
board.
3. Observing diode polarity, wrap each lead of the new diode
around the corresponding lead on the circuit board
4. Securely crimp each connection and solder it
5. Inspect (on the circuit board copper side) the solder joints of
the two "original" leads. If they are not shiny, reheat them
and, if necessary, apply additional solder.
Fuse and Conventional Resistor Removal/Replacement
1. Clip each fuse or resistor lead at top of circuit board hollow
stake
2. Securely crimp leads of replacement component around
notch at stake top
3. Solder the connections
CAUTION: Maintain original spacing between the re-
placed component and adjacent components and the cir-
Cuit board, to prevent excessive component tempera-
tures.
Circuit Board Foil Repair
Excessive heat applied to the copper foil of any printed circuit
board will weaken the adhesive that bonds the foil to the circuit
board, causing the foil to separate from, ог "lift-otf", the board.
The following guidelines and procedures should be followed
whenever this condition is encountered
In Critical Copper Pattern Areas
High component/copper pattern density and/or special voltage/
current characteristics make the spacing and integrity of copper
pattern in some circuit board areas more critical than in others.
The circuit foil in these areas is designated as Critica! Copper
Pattern and is identified and iliustrated in this service data in the
section titled Safety Related Copper Pattern (see table of con-
tents for page number). Because Critical Copper Pattern requires
special soldering techniques to ensure the maintenance of relia-
bility and safety standards, contact your local RCA Consumer
4
Electronics Distributor Service Manager before attempting repair
of Critical Copper Pattern
At IC Connections
2. Carefully scratch away the solder resist and acrylic coating (if
used) from the end of the remaining copper pattern
CRIMP AND
SOLDER
install Jumper Wire and Solder
3. Bend a small "U" in one end of a small-gauge jumper wire
and carefully crimp it around the IC pin. Solder the IC con-
nection
4. Route the jumper wire along the path of the cut-away copper
pattern and tet it overlap the previously scraped end of the
good copper pattern. Solder the overlapped area, and clip off
any excess jumper wire.
At Other Connections
2. Trace along the copper pattern from both sides of the pattern
break and locate the nearest component that is directly con-
nected to the affected copper pattern
3. Connect insulated 20-даиде jumper wire from the lead of the
nearest component on one side of the pattern break to the
lead of the nearest component on the other side. Carefully
сгітр and solder the connections.
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CRIMP AND
_SOLDER
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insulated Jumper Wire
CAUTION: Be sure the insulated jumper wire is dressed
зо that it does not touch components or sharp edges.
F013.4.2