HP 8560A

Note
The on-screen amplitude level will probably not change as expected, since the
video circuitry is assumed to be faulty.
15. Monitor A3TP14 while stepping the reference level from -10 dBm to +30 dBm. If the
voltage does not step approximately 100 mV per 10 dB step, refer to “Video MUX” in
this chapter.
16. If the Video MUX is working properly, monitor A3TP15 with the oscilloscope and step
the reference level from -10 dBm to f30 dBm. If the voltage does not change 100 mV
per 10 dB step, refer to “Video Filter” in this chapter.
17. If the voltage at A3TP15 is correct, move the oscilloscope probe to A3TP17 and step the
reference level between -10 dBm and +30 dBm. If the voltage does not change 100 mV
per 10 dB step, refer to “Video Filter Buffer Amplifier” in this chapter.
18. If the voltage at A3TP17 is correct, move the oscilloscope probe to A3TP6. Set the
following controls to keep the ADC MUX set to the MOD-VIDEO input during the
sweep.
SWEEP TIME
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..~OS
DETECTORMODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SAMPLE
19. Step the reference level from -10 dBm to +30 dBm while monitoring the voltage change
on the oscilloscope. If the voltage does not change 100 mV per 10 dB step, refer to “ADC
MUX” in this chapter.
20. If the voltage at A3TP6 is correct, move the oscilloscope probe to A3TP8 and step the
reference level between -10 dBm and +30 dBm. If the voltage at A3TP8 is not the same
as that at A3TP6, replace A3UllO.
21. If the voltage at A3TP8 and A3TP6 are equal, move the oscilloscope probe to A3TP7.
ADC/lnterface Section 7-13