Page 122 - Testing Electronic Components

Points to remember when replacing transistor with substitutes:

• Polarity of the transistor i.e. whether it is PNP or NPN.
• Substitute transistor should have almost same voltage, current and
wattage rating.
• Whether transistor which is being replaced is of low frequency or high
frequency type.

• Whenever replacing transistor see that base, collector and emitter are
soldered in their proper position.
• While replacing transistor desoldering pump must be used and
soldering iron should not be kept for longer time, it may damage the
transistor as well as printed circuit board.
• Transistor used for output circuit must have proper heat sink. If
supply is given without heat sink the transistor may get damaged.
• Whenever replacing horizontal output, switching output or power
output transistor it should be kept in mind that mica sheet being used
should not be broken, otherwise output transistor collector will short
with body and it will go off immediately or the supply voltage will
drop.

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