HP 8672S Operating And Service Manual page 100

Service
Models 8672S/86720A
SERVICE SHEET 2 (cont'd)
If the program runs correctly, the FEU is operat¬
ing correctly in remote. However, it is possible that
a problem exists in the Signal Generator. Some of
the remote functions that affect the FEU are con¬
trolled by the Signal Generator. For example,
although the step attenuator is in the FEU, the
attenuator setting must be sent to the Signal Gen¬
erator. Refer to Section 3 of this manual for adddi-
tional information on programming the Signal
Generator System. Refer to the HP 8672A Operat-
ing and Service Manual to troubleshoot the Signal
Generator HP-IB circuits.
If the program is not running correctly, continue
with this procedure. If the front panel meter is the
only malfunction in remote operation, skip to
step 9.
NOTE
If an incorrect result occurs in any of the
following steps, refer to the applicable
service sheet .and check the inputs to the
circuit that failed.
4. Probe A5U4 pins 6 and 9 with the logic probe to
verify that the one-shots are working. If they
are not, check if the handshake signals shown
in Figure 8-2 are present. Stop and restsart the
program as required to check these signals.
5. Probe A4U2 pin 5 to verify the pulse that
triggers the decoders is present.
6. Verify A4U9B pin 9 (Listen flip-flop) is high.
7. Verify A4U4A pin 12 (Remote/Local logic) is
high.
8. Verify A5U5 pin 14 (Address Comparator)
pulses.
NOTE
The remote level circuits are located on
the A10 ALC Amplifier Assembly (Serv¬
ice Sheet 7).
9. Halt the program and send the following
command:
OUTPUT 728; "A1234"
10. Verify the inputs to the remote level DAC at
A10U15 pins 5, 6, 7, and 8 are high.
11. Send the following command:
OUTPUT 728; "B1234"
12. Verify the inputs at A10U15 pins 5, 6, 7, and 8
are low. If the inputs to the DAC are correct,
troubleshoot the remote level circuits on the
A10 ALC Amplifier Assembly. If the inputs
are incorrect, trace the signal back through
the A2 Driver Assembly to determine where
the control signal is lost.