Video Filter Buffer Amplifier; Positive/Negative Peak Detectors; Table 7-7 A3U102 Latch Outputs - HP 8560E Service Manual

ADC/Interface Section
A3 Assembly Video Circuits
Table 7-7 A3U102 Latch Outputs
Video BW
300 Hz
1 kHz
3 kHz
10 kHz
30 kHz
100 kHz
300 kHz
1 MHz
3 MHz
Video Filter Buffer Amplifier
The video filter buffer amplifier provides outputs for video trigger,
positive and negative peak detectors, and the analog zero-span (sweeps
<30 ms). The zero-span video output is terminated in 500 ohms on the
A2 Controller assembly. The amplifier is a high-input-impedance buffer
amplifier with a gain of one when properly terminated.
Current source U307C provides twice the current of Q316. Resistor
R145 and current source U307D shift the dc level. Resistor R260
terminates the peak detector inputs in 500 ohms. The unterminated
gain is 1.1. Diode CR114 prevents latchup during positive overdrive
conditions while CR113 protects Q318 during overdrive. Diode CR117
is a 12.7 V zener that limits the peak detector output to +1.5 V.
Typically, limiting occurs at +1.1 V.

Positive/Negative Peak Detectors

Refer to function blocks Y and Z of A3 Interface Assembly Schematic
Diagram (sheet 5 of 6) in the
Component Level Information
The following information pertains to the positive peak detector and is
applicable to troubleshooting the negative peak detector.
The positive peak detector consists of an input amplifier (A3U204 and
374
or
SWEEP CONT SGL
Pin Pin
2 5
H L
L L
L H
L L
H L
L L
L H
L L
L L
Refer to function block W of A3 Interface Assembly Schematic
Diagram (sheet 5 of 6) in the
Component Level Information
.
PRESET
Pin Pin Pin
7 10 12
L L L
L L L
L L L
L L H
H L L
H L L
H L L
H L H
L H L
HP 8560 E-Series Spectrum Analyzer
.
HP 8560 E-Series Spectrum Analyzer
.
Pin
15
L
H
L
L
L
H
L
L
L
Chapter 7