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12-4-2
9-4 PCB Inspection
9-4-1 Cautions for Part Replacement
1. The human body carries much static electricity.
Before touching a part for repair, replacement or the
similar purpose, be sure to touch a grounded metal-
lic portion by hand to let the static electricity go
through the metallic portion to the earth.
Especially when handling any micro computer or IC,
carefully remove such static electricity before touch-
ing them.
2. When repairing any part on a work bench, be sure
to place an insulative sheet on the bench and always
keep the sheet surface neat without any metal frag-
ments. If any such fragment touches a part, a sec-
ondary trouble will possibly be caused in the part.
3. Before replacing any parts, be sure to turn off the
power supply. If such replacement is done with the
power supply kept on, an electric shock, short circuit
or destruction of a part may result.
4. During replacement or repair of a part, carefully han-
dle it : The printed circuit board has fine lead wires
(jumper wires) and glass-made parts (diode) on its
substrate.
So if a circuit board is roughly handled, such lead
wires and parts will be easily broken or damaged by
bending or shock.
5. When soldering the lead wires of any new part, be
sure to polish them using an emery paper or the like
before soldering them.
Since the lead wires of any new part are covered
with an oxide film, solder cannot adhere to the lead
wires if not polished.
9-4-2 Procedure
The parts should be replaced in the following procedure.
6. When soldering any part, care should be exercised
not to apply any high-wattage soldering iron to the
part for a long time. Some parts are of so low a heat
resistance that they may be broken or have the
properties changed if a soldering iron is so applied
(Otherwise, the pattern may possibly be separated
and raised).
7. The heat of the soldering iron should be transferred
to the entire object to be soldered. If the solder
pieces are not well fused due to insufficient transfer
of the heat from the soldering iron, no satisfactory
electrical continuity can be assured even if the sol-
dered objects appear well connected to each other.
8. The solder used should be limited to a minimum.
If excessive solder is used, it will cause inter-pattern
contact, which may cause malfunction of the circuit.
9. Although some part of the PCB surface are coated
with coating material for protection from dust and
dirt, soldering is also available to the coating part.
Because this coating is thin and is weak for solder-
ing heat.
But coating material remaining on the solder part
should be cleaned up before soldering a new
component to prevent the solder part from becoming
bad conduction.
The repair is completed.
Check the operation of the new part.
Replace it with a new part.
Detach the faulty part.
Check for any faulty part.
Samsung Electronics 9-18