HP 8562E, Service Manual

Page: 281 / 482

Problems
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
high, generating The CPU determines the
key pressed by setting only one keyboard scan line (LKSCNO through LKSCN5) low through
and reading the keyboard sense lines.
1.
2.
If none of the keys or RPG responds, check ribbon cable, (This cable connects
the 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
might be an open or shorted wire in AlAlWl.
Table 8-4. Keyboard Matrix
LKSNSO LKSNS3
LKSCNO
SAVE R E C A L L
MODULE TRIG DISP 9
P E A K
BW TRACE 8
SEARCH
FREQ AUTO 7
COUNT COUPLE
LKSCN4
SWEEP
SK1 SK2 SK3
LKSCN5
AUX
CAL SGL
CTRL
LKSNS4 LKSNS5
MHz Hz
6 3 BK SP
5
4
SK4
COPY
2
1
SK5
FRE-
QUENCY
0
SK6
SPAN
3. Check that all inputs to NAND gate (LKSNS lines) are high when no key is
pressed. If any input is low, continue with the following:
a. Disconnect AlAlWl from and again check all inputs to
b. If any input is low with AlAlWl disconnected, suspect or
c. Reconnect AlAlWl to
4. Monitor 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 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 when a key is pressed.
7. Check that only one input to (LKSNS lines) goes low when a key is pressed.
8. Check that pin 9 (LKBD-RESET) pulses low when a key is pressed.
Section 8-7