14: Maintenance
PRC1099A-MS
14-15
1. Connect one lead of the ohmmeter to the base.
2. Connect the other lead first to the collector and then to the emitter.
3. Reverse the polarity of the ohmmeter leads and repeat the test. This
test should indicate high resistance with the leads in one polarization
and low resistance in the other. Only in rare instances does a transistor
that passes this test prove to be faulty in other ways.
4. Use a DVM to make a simple in-circuit check of a transistor. The
potential across the base-emitter junction should be about 0.7V. A
substantial difference indicates a fault in the transistor or in the
surrounding circuitry.
14.4.4
Integrated Circuits
Complex internal IC circuitry makes it impractical to do any analytical fault
detection on IC devices, however the following guidelines can help to locate a
fault in circuits with IC components:
1. Isolate the fault to a particular stage. Check pin voltages against
typical values given in the manufacturer’s specification charts.
2. If there are any substantial variations, check the surrounding circuit
components.
3. Check the IC through substitution.
14.5
Component Replacement
All transceiver printed circuit boards are heavy epoxy fiberglass with 2 oz.
tinned copper foil, meeting applicable military specifications. Faults in the
boards are not likely to occur, unless they are handled improperly when
replacing components. If you follow correct component preparation and
soldering procedures, you can replace components many times without
damaging the board. Most integrated circuit (IC) components are installed in
sockets for easy replacement.
For easy component replacement, begin with the correct tools. The soldering
iron must have a small, instrument-type tip, no larger than the circuit board
pads.
CAUTION: Do not use a tiny, low temperature, instrument type
iron; the soldering iron must heat the solder
sufficiently to melt the it quickly, otherwise component
and/or board damage can occur.
1. Use the soldering iron to melt the solder at the connection.
2. While the solder is still molten, remove it with a desoldering tool.
