Variable Gain Amplifier (Vga); Track And Hold - HP 8560A Service Manual

Variable Gain Amplifier (VGA)

See function block AB of A3 Interface Assembly Schematic Diagram (sheet 6 of 6).
The VGA provides adjustable gain in the video path. Its nominal gain of 7 can be adjusted
are set to the same value.) The DAC settings cannot be changed from the front panel.

Track and Hold

See function block AC of A3 Interface Assembly Schematic Diagram (sheet 6 of 6).
1. Press [PRESET) on the HP 8560A and set the controls as follows:
C E N T E R F R E Q
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz
DETECTOR MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sample
REF LVL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -70 dBm
LOG dB/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..2dB/div
SWEEP TIME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50ms
2. Disconnect any signal from the analyzer input. A full scale display of sampled noise should
be present.
3. Trigger an oscilloscope on the positive going edge of HHOLD (A3U506 pin 16).
4. The waveform at A3TPlO should be random noise with an average level of approximately
4 V. The noise should have a flat spot in its response while HHOLD is high, indicating
proper operation of U114.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz