Table 11-2. Automatic Fault Isolation References
Suspected Circuit Indicated
by Automatic Fault Isolation
Check the YTO loop
Check first LO
Check first LO pretune frequency and amplitude
Check the fractional N oscillator
Check 3rd LO drive
Check 10 MHz reference to phase/frequency
detector
Check for 10 MHz signal at other input to
phase/frequency detector
Check A3 ADC MUX function block
Check Al4 frequency control assembly
Check A14J301 10 MHz REF input
Check Al5 RF assembly
Check current source
U307
Check FM loop sense
Check YTF gain and offset DACs
Check level at amplifier Input
Check levels into mixer
U400
Check loop references
Check main coil tune DAC
Check main coil coarse and fine DACs
Manual Procedure to Perform
Confirming a Faulty Synthesizer Section
(steps 12-33)
Confirming a Faulty Synthesizer Section
(steps 9-11)
Unlocked YTO PLL (steps
9-12)
Unlocked YTO PLL (steps 13-17)
Third LO Driver Amplifier (steps l-6)
Unlocked Reference PLL (steps d-13)
Unlocked Reference PLL (steps 12 and 13)
Confirming a Faulty Synthesizer Section
(steps
1-d)
Confirming a Faulty Synthesizer Section
(steps 12-18)
Confirming a Faulty Synthesizer Section
(steps 5-8)
Confirming a Faulty Synthesizer Section
(steps 18-25)
First LO Span Problems (All Spans) (steps
14-21)
Unlocked YTO PLL (steps
27-34)
YTF Driver Circuit (steps
10-23)
Third LO Driver Amplifier (steps l-6)
Unlocked Offset PLL (steps
3-13)
Unlocked Offset PLL (steps 1 and 2)
Unlocked YTO PLL (steps
45-49)
Unlocked YTO PLL (steps 41-44)
1 l-4 Synthesizer Section