RPG Interface
See function block J of A3 Interface Assembly Schematic Diagram (sheet 3 of 6).
U608B latches the RPG direction from the two RPG outputs,
RPG-01
and
RPG-02.
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.
1. Monitor
A3U401
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. Set the
m
switch off and disconnect AlAlWl from A3J602. Jumper A3U608 pin
12
(RPG-01)
to
U608
pin 14
(f5
Vdc). Jumper
U401
pin 2 (RPG-02) to U511 pin 11
(HDPKD-CLK). Th
isp
rovides a 7.8 kHz square wave to the RPG-02 input of the RPG
Interface.
6. Set the
m
switch on.
7. Check A3U608 pin 9 for narrow, low-going pulses approximately every 90 ms.
8. Check A3U608 pin 13 (LRPG-RESET) f
ornarrow, 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) f
or 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) f
or 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 7-5 and check the
frequencies at divide-by-16 counter
A3U606.
14. If all the checks above are correct but the analyzer does not respond to the RPG, suspect
a problem in either the
AlA
RPG or the
AlAl
Keyboard.
15. Set the [LINE] switch off.
16. Reconnect AlAlWl to
A3J602 and remove all jumpers.
7-8
ADC/lnterface
Section
To Next Page
Loading...
