Rpg Interface - HP 8560E Service Manual

5. Check that the LKSCN lines (outputs of A3J602 pins 1 through 6)
6. Check that a pulse is present at each LKSCN output of U602 when a
7. Check that only one input to U607 (LKSNS lines) goes low when a
8. Check that U602 pin 9 (LKBD_RESET) pulses low when a key is
9. If LKBD_RESET is incorrect and a pulse is not present at each of

RPG Interface

U608B latches the RPG direction from the two RPG outputs,
RPG_COUNT and RPG_COUNT1. 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.
Elsewhere, RPG_COUNT1 is referred to as RPG_01 and RPG_COUNT
NOTE
is referred to as RPG_02.
1. Monitor A3U401 pin 2 with a logic probe or oscilloscope. Pulses
2. Monitor A3U608 pin 12 as the RPG is rotated. Pulses should be
3. If pulses are missing at both points, check for power and ground
4. If pulses are missing at only one point, check for an open or short on
5. Press
Chapter 7
read a TTL low with no key pressed. (Any TTL high indicates a
faulty A3 Interface assembly.)
key is pressed.
key is pressed.
pressed.
the LKSCN outputs of U602 when a key is pressed, check for
LWRCLK and LSCAN_KBD.
Refer to function block J of A3 Interface Assembly Schematic
Diagram (sheet 3 of 6) in the
Component Level Informatio
should be present as the RPG is rotated.
present.
signals to A1A1W1 and A1A2W1. If both power and ground are
there, the A1A2 RPG is probably defective.
A1A1W1 and A1A2W1. If these cables are working properly, A1A2
RPG is probably defective.
to turn spectrum analyzer off and disconnect A1A1W1
LINE
from A3J602. Jumper A3U608 pin 12 (RPG_COUNT) to U608 pin 14
(+5 Vdc). Jumper U401 pin 2 (RPG_COUNT1) to U511 pin 11
(HDPKD_CLK). This provides a 7.8 kHz square wave to the
HP 8560 E-Series Spectrum Analyzer
n.
ADC/Interface Section
Keyboard/RPG Problems
361