Model 2500A225C
48
Rev A
4.3 COOLING SYSTEM
The 2500A225C is air cooled using DC fans for stable and efficient cooling.
Select an operating location that will permit air to circulate freely around the amplifier’s cabinet. The
Model 2500A225CC utilizes air cooling and should be located where the normal flow of air into or exiting from
the unit will not be restricted, diverted, or re-circulated through the unit itself; in particular, the flow of warm
air exiting the rear of the amplifier should not be impeded.
Do not position the unit next to a wall or other equipment that would restrict the flow of air into the front and
sides of the unit or out of the rear of the unit. If possible, leave approximately 3 inches (7.6cm) of unimpeded
space on the sides of the amplifier and at least 1 meter of space from the rear of the amplifier.
4.4 TROUBLESHOOTING
CAUTION:
The transistors used in the Model 2500A225C amplifier are LDMOS
transistors. These devices are very reliable when installed in a suitable
circuit, but they can be easily damaged by improper troubleshooting or
handling techniques.
Use caution when troubleshooting the LDMOS; do not short the gate to
the ground or to the drain.
CAUTION:
Use care when unpacking new LDMOS. The LDMOS packaging should
only be opened at Electrostatic Discharge (ESD)-approved workstations,
by individuals who are familiar with the handling of LDMOS and other
ESD-sensitive devices.
Troubleshooting the Model 2500A225C in a logical manner can speed the solution to a problem. The settings
of potentiometers (pots), capacitors (caps), or other variables should not be disturbed until other problems have
been eliminated. Comparing the measured DC voltages to those shown on the schematics can solve many
problems. Before measuring circuit voltages, first verify that the voltages to the circuits are correct.
Model 2500A225C troubleshooting symptoms and remedies are described in the sections that follow
4.4.1—General: Reading Faults
4.4.2—The Unit Cannot be Operated Remotely
4.4.3—Thermal Fault
4.4.4—Interlock Fault
4.4.5—Power Supply Faults
4.4.6—Amplifier Faults
4.4.7—ALC Fault
4.4.8—Low or No Power Output (DC Tests)
4.4.9—Low or No Power Output (RF Test)
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