Agilent Technologies 856290216 service manual Analog Bus Timing

13.Check that address lines A0 through A7 and data lines DO through D7 are all high. If all address and data lines are high, suspect a fault either in W2 or one of the other four assemblies which connect to W2.

14.If any address or data line is low, check the appropriate input of either U405 (data lines) or U406 (address lines).

15.If a data line input is stuck low, check the data bus buffer. If an address line input is stuck low, check A3Wl and the A2 controller assembly.

16.If the appropriate input is high or toggling between high and low, suspect a failure in either U405 (data lines) or U406 (address lines).

17.Remove jumpers.

Analog Bus Timing

Refer to function block P of A3 Interface Assembly Schematic Diagram in the HP 8560 E-Series Spectrum Analyzer Component Level Information.

Analog bus timing (ABT) generates the strobes for the A4, A5, A14, and Al5 assemblies. The Al4 frequency control assembly also requires a qualifier for its strobe, LVFC-ENABLE. A3U400 and A3U414 provide a 2 ps delay between the time HANA-BUS goes high and the enable line to demultiplexer A3U407 goes low.

1. Press [PRESET) on the spectrum analyzer and set the controls as follows:

Center frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..lOOMHz

2.Check that A3U407 pin 1 goes low approximately 2 ps after HANA-BUS (A3U400 pin 3) goes high.

3.If HANA-BUS is absent, check for pulses on ABT A3U505 pin 2 and IA10 (A3U505 pin 5).

4.If A3U407 pin 1 is not delayed 2 ps from HANA-BUS, check for the presence of the

1MHz HBADC-CLKO.

5.If A3U407 pin 1 is not delayed 2 ps from HANA-BUS and HBADC-CLKO is correct, suspect a fault in either A3U414 or A3U400.

6.Press (PRESET) and set the controls as follows:

Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz Trigger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..SINGL E

7.Monitor A3U401 pin 3 (LR-STB) with an oscilloscope or logic probe. This is the strobe for the Al5 RF assembly.

8.Press (AUXCTRL) and RIZAR PANEL and check that pulses occur when toggling between 10 MHz IlllT and 10 MHZ EXT.

9.Monitor A3U401 pin 5 (LF-STB) with an oscilloscope or logic probe. This is the strobe for the Al4 frequency control assembly.

10.Press [AMPLITUDE) and check that pulses occur when toggling between AT”Tl!X settings of 10 and 20 dB.

ADC/lnterface Section 8-29