Maintenance
6-12 1705A Spectrum Monitor
all obvious defects. In the case of overheatedcomponents, determine and
correctthe cause of overheating before re-applying power.
5. Use successive electrical checks to locate t he source of the problem.The
primary tool for problemisolation is the oscilloscope. Use the Performance
Check Procedure (located in Section 5) to determi ne if aci rcuit is operating
within specifications. At times it may be necessary to chan ge acal ibration
adjustment to determineif a circuit is operational, but since this can destroy
instrument calibration,care should be exercised. Before changing an
adjustment, note its position so that it canbe returned to its original setting.
6. Determinethe extent of the repair. If the necessary repair is complex, it may
be advisable to contactyour local Tektronix field office or representative
beforecontinuing. If the repairis minor, such as replacing a component, see
the parts list for replacement information. Removal and replacement
proceduresfor the assemblies can be found under Corrective Maintenance.
Power Supply TroubleshootingProcedureNOTE. A reviewof the power supply theory of operation is recommendedbefore
attempting repairs.
The equipment neededto troubleshootthe power supply:
HDigital Multimeter (DMM), with a diode checkfunction
HOscilloscope
H0 to 20 Vdc VariablePower Supply
HClip Lead --to short across a component
HHigh VoltageProbe, ≥1GΩinputresistance
The TroubleshootingProcedure for the Power Supply (Assembly A1) is split into
two sections, the Low Voltsand High Volts Supplies. Start the procedureby
determining whichsection of the Power Supply the problem is in. Apply ac
power and turn on the Power Supply. From Table6--2, determine which
symptom the Power Supply exhibits and referto the corresponding procedure.
Table6- 2: Power Supply Fault Symptoms
Symptom Procedure
Line fuse open Rectifier/Switcher Check (Low Volts)