HP 8562E Service Manual page 281

Refer to function block G of A3 Interface Assembly Schematic Diagram in the
HP 8560 E-Series Spectrum Analyzer Component Level Information.
A pressed key results in a low on a keyboard sense line (LKSNSO through LKSNS7). This sets
the output of NAND gate U607 high, generating KBD/RPG-IRQ.
key pressed by setting only one keyboard scan line (LKSCNO through LKSCN5) low through
1. If none of the keys or RPG responds, check ribbon cable, AlAlWl. (This cable connects
the AlAl keyboard to the A3 interface assembly.) The keys are arranged in a row/column
matrix, as shown in Table 8-4.
If an entire row or column of keys does not respond, and the RPG does respond, there
2.
might be an open or shorted wire in AlAlWl.
LKSNSO
LKSCNO
MODULE
P E A K
SEARCH
FREQ
COUNT
LKSCN4
SWEEP
LKSCN5
AUX
CTRL
3. Check that all inputs to NAND gate A3U607 (LKSNS lines) are high when no key is
pressed. If any input is low, continue with the following:
a. Disconnect AlAlWl from A3J602 and again check all inputs to U607.
b. If any input is low with AlAlWl disconnected, suspect A3U604, A3U607, or A3U602.
c. Reconnect AlAlWl to A3J602.
4. Monitor A3U607 pin 8 with a logic probe. A TTL high should be present when any key is
held down. Monitor this point while pressing each key in succession.
5. Check that the LKSCN lines (outputs of A3J602 pins 1 through 6) read a TTL low with no
key pressed. (Any TTL high indicates a faulty A3 Interface assembly.)
6. Check that a pulse is present at each LKSCN output of U602 when a key is pressed.
7. Check that only one input to U607 (LKSNS lines) goes low when a key is pressed.
8. Check that U602 pin 9 (LKBD-RESET) pulses low when a key is pressed.
Table 8-4. Keyboard Matrix
R E C A L L GHz
SAVE
DISP
TRIG
BW TRACE
AUTO
COUPLE
SK1 SK2
CAL
The CPU determines the
LKSNS4 LKSNS5
MHz
9
6 3
8
5 2
7 4 1
SK4 SK5
SK3
SGL FRE-
COPY
QUENCY
Hz
BK SP
0
SK6
SPAN