Agilent Technologies 856290216 Peak Detector Reset, HMUX-SELO/l versus Detector Mode

7.If the peak detector appears latched up, check LPOS-RST (U422 pin 4) for a negative TTL level reset pulses. The reset pulses should occur every 130 ps and should be approximately 250 ns wide.

8.If the reset pulses are absent, troubleshoot the Peak Detector Reset circuitry.

9.If the reset pulses are present, check the gate of Q207. The pulses should be positive-going from -12.7 V to -1.35 V.

10.The peak detector can be made into a unity gain amplifier by shorting the, cathode of CR203 to the anode of CR204. If the peak detector functions normally as a unity gain amplifier, suspect Q208 or CR203 or CR204.

Peak Detector Reset

Refer to function block R of A3 Interface Assembly Schematic Diagram in the

HP 8560 E-Series Spectrum Analyzer Component Level Information.

1. Press (“1 on the spectrum analyzer and set the controls as follows:

Center frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..300MHz Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz Sweep time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 s Detector mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . POS PEAK

2.Check that HHOLD (A3U526 pin 11) h as 18 ps wide pulses every 128 pus.

3.Check that HODD (U408 pin 5) is a square wave with a period of 16.7 ms (2 x sweep time/600).

4.Check LPOS-RST (U422 pin 4) for 200 ns low-going pulses every 128 ps.

5.Check LNEG-RST (A3U422 pin 12) for 200 ns low-going pulses every 128 ps.

6.Set the detector mode to NORMAL and check that LNEG-RST (A3U422 pin 12) has two pulses spaced 40 ps apart and then a single pulse approximately 88 /.LS from the second pulse.

7.Check HMUX-SELO (A3U408 pin 3) and HMUX-SELl (A3U408 pin 9) according to Table 8-8.

Table 8-8. HMUX-SELO/l versus Detector Mode

Detector Mode	HMUX-SELO (U408 pin 3)	HMUX-SELl (U408 pin 9)
NORMAL	15 ps pulse every 128 ps	40 ps pulse every 128 ps
SAMPLE	H	H
POS PEAK	H	L
NEG PEAK	L	H

8-20 ADC/lnterface Section