Check A3 ADC MUX Function Block (steps 1-4)
1. Connect the positive lead of a DVM to
A15J200
pin 13 and the negative lead to
A15J200
pin 6. This measures the sampling oscillator tune voltage which is an input to the A3
interface assembly ADC MUX.
2. Set the spectrum analyzer to the following settings:
Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz
Center frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389.5 MHz
Trigger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Single
3. Use the data entry keys to tune the CENTER
FREQ
to the values listed in Table 11-4.
4. As the sampling oscillator frequency is increased, the DVM reading should also increase.
If the tune voltage is correct, but the ADC measures the voltage and determines it to be
out of specification, troubleshoot the A3 assembly ADC MUX.
Table 11-4. Center Frequency Tuning Values
HP 85623 sampling
Center Frequency (MHz) Oscillator Frequency (MHz)
2156.3 285.000
2176.3,
286.364
2199.5 287.500
2230.3 288.462
799.3 288.889
2263.3 290.000
2282.3 290.909
2302.3
291.667
2155.3 292.500
2158.3 293.478
2336.3 294.444
2196.3 295.000
1.3
296.000
2378.3 296.471
2410.3 297.000
2422.3 297.222
Check
A14J301
10 MHz reference input (steps 5-8)
5. Disconnect W37 from A14J301.
6. Connect a test cable from W37 to the input of another spectrum analyzer. Tune the other
spectrum analyzer to the following settings:
Center frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..lO MHz
Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
..2MHz
7. The amplitude of the 10 MHz reference signal should measure >-1
dBm.
If the signal
does not measure >-1
dBm,
troubleshoot the 10 MHz distribution on Al5 and A21
OCXO (If not Option 103).
8. Reconnect W37 to
A14J301.
Synthesizer Section
1 l-9