Maintenance
2715 Spectrum Analyzer Service Manual 6-7
In most cases, circuit numbers are assign ed according to the physical location of
the component on the board or assembly.The first digit designates the row of a
grid and the second a column.
General TroubleshootingTechniques. Before using test equipment to measure
across static sensitive componentsor assemblies, be certain that voltages and
currents supplied by the test equip ment do not exceed the limits of the compo-
nents to be tested.
Try to isolate theproblem to a component through signal analysis. Determine
that circuit voltages will not dam age the replacement.
Semiconductor Checks. Semiconductor failures account for the majority of
electronic equipment failures.All semiconductors are soldered to the boards to
reduce pin contact problems.F ollow theseguidelines when substituting any of
these semiconductors.
HAlways turn the power offbefore removing an assembly or circuit board.
HUse a hot air repair terminal to remove surfacemounted components, and a
15 W or less soldering iron to removecomponents with leads.
HUse only good components for substitution. Be sure the new component is
inserted into the board properlybefore soldering. Refer to the manufacturer’s
data sheet for integratedcircuit and transistor lead configuration.
Diode Checks. Most diodes can be checked in the circuit by tak ing measurements
across the diode and comparingthese with voltages listed on the diagram.
Forward to back resistance ratios can usual ly be taken by referring to the
schematic and pulling appropriatetransistors and pin connectors to remove low
resistance loops around the diode.
NOTE. Do not use an ohmmeter scale with a high external currentto check diode
junctions. Do not check the forward to back resistanceratios of mixer diodes.
Diagnostic Firmware. The firmware in the Spectrum Analyzer providesdiagnostic
routines that can be used to troubleshootthe Frequency Control system.