Agilent Technologies 856290216 service manual RPG Interface

9.If LKBD-RESET is incorrect and a pulse is not present at each of. the LKSCN outputs of U602 when a key is pressed, check for LWRCLK and LSCAN-KBD.

RPG Interface

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

HP 8560 E-Series Spectrum Analyzer Component Level Information.

U608B latches the RPG direction from the two RPG outputs, RPG-COUNT and RPG-COUNTl. Counterclockwise RPG rotation produces low-going pulses which result in a high output on U608B. Clockwise RPG rotation results in a low output from U608B. U612A provides the edge to trigger one-shot U423B, which generates a 90 ms pulse. This pulse gates U610A for counting of RPG pulses by U606. Gates U610D and U614D prevent retriggering of U423B until its 90 ms pulse has timed out.

Note	Elsewhere, RPG-COUNT1 is referred to as RPG-01 and RPG-COUNT is
	referred to as RPG-02.

1.Monitor A3U4Ol pin 2 with a logic probe or oscilloscope. Pulses should be present as the RPG is rotated.

2.Monitor A3U608 pin 12 as the RPG is rotated. Pulses should be present.

3.If pulses are missing at both points, check for power and ground signals to AlAlWl and AlA2Wl. If both power and ground are there, the AlA RPG is probably defective.

4.If pulses are missing at only one point, check for an open or short on AlAlWl and AlA2Wl. If these cables are working properly, AlA RPG is probably defective.

5.Press LUNE) to turn spectrum analyzer off and disconnect AlAlWl from A3J602.

Jumper A3U608 pin 12 (RPG-COUNTl) to U608 pin 14 (+5 Vdc). Jumper U401 pin 2 (RPG-COUNTl) to U511 pin 11 (HDPKD-CLK). This provides a 7.8 kHz square wave to the RPG-COUNT input of the RPG Interface.

6.Press (LINE) to turn spectrum analyzer on.

7.Check A3U608 pin 9 for narrow, low-going pulses approximately every 90 ms.

8.Check A3U608 pin 13 (LRPG-RESET) for narrow, low-going pulses approximately every 90 ms.

9.Check A3U612 pin 5 for narrow, low-going pulses approximately every 90 ms.

10.Check U608 pin 5 (HRPG-IRQ) for narrow, high-going pulses approximately every 90 ms.

11.If HRPG-IRQ is correct but LRPG-RESET is incorrect, check U505 pin 13 (LKBD/RPG-IRQ) for narrow, low-going pulses approximately every 90 ms.

12.If HRPG-IRQ and LKBD/RPG-IRQ are correct but LRPG-RESET is incorrect, suspect a failure on the A2 controller assembly.

13.Check U610 pin 3 for a 7.8 kHz square wave. Check U606 pin 2 (HRPG-RESET) for narrow, high-going pulses approximately every 90 ms. Refer to Table 8-5 and check the frequencies at divide-by-16 counter A3U606.

14.If all the checks above are correct but the spectrum analyzer does not respond to the RPG, suspect a problem in either the AlA RPG or the AlAl Keyboard.

8-8 ADC/lnterface Section