TM9100 Service Manual Frequency Synthesizer Fault Finding 173© Tait Electronics Limited August 20059.2 Power SuppliesIntroduction First check that a power supply is not the cause of the fault. There are fourpower supplies for the frequency synthesizer — two are supplied from thePSU (power supply unit) module and two are produced in the synthesizercircuitry itself:■ Task 3: 14 V DC supply from SMPS (VCL SUPPLY)■ Task 4: 6 V DC supply from 6 V regulator in PSU module (+6V 0)■ Task 5: 5 V DC supply following filtering of 6 V supply (+5 V DEC)■ Task 6: 3 V DC supply from 3 V regulator in PSU module (+3V 0 AN)The measurement points for diagnosing faults in the power supplies aresummarized in Figure 9.1.Figure 9.1 Measurement points for the frequency synthesizer power supply circuitryPIN 4 OFQ508PIN 4 OFQ508PIN 4 OFIC606PIN 4 OFIC606PIN 5 OFIC606PIN 5 OFIC606Q500 ANDR533Q500 ANDR533PINS 7 AND 15OF IC503PINS 7 AND 15OF IC503SIGNAL TYPESRFANALOGCLOCKDIGITALPLL14 VSMPSLOOPFILTERANDSUMMERFILTERINGOF SUPPLYFOR PLLAND LOOPFILTERFILTERINGOF SUPPLYFOR VCOCIRCUITRY3 VSUPPLYVCOCIRCUITRYFREQUENCYSYNTHESIZERINTERFACECIRCUITRYINVERTERJUNCTION OFC531 AND R530JUNCTION OFC531 AND R530+3V0 ANL5069 VSUPPLY6 VSUPPLYAGND+9V0+6V0VCL SUPPLY+5V DEC
