Switch Closure Command Table; Acv And Acv+Dcv Failure Isolation - HP 3456A Operating And Service Manual

Model 3456A
B·E·I. GENERAL.
8-E-2. This Service Group
ACV + DCV troubleshooting
3456A. You must make sure the 3456A is functioning
correctly in the DCV Function, before troubleshooting
for any ACV or ACV + DCV Malfunctions. (Go to Ser­
vice Group C if the DCV Function fails).
8-E-3. The Service Group is symptoms oriented (what
fails) with two major levels of troubleshooting. The first
level uses procedures to determine which area in the AC
Converter causes the failure. The second level has infor­
mation to troubleshoot the faulty area.
NOTE
The A C Converter has to be readjusted ac­
cording to the ACV A d justment Procedure
in Service Group F . if any components are
replaced in the converter.
B·E·4. PRE·TROUBLESHOOTlNG INFORMATION.
8-E-5. Various Switching FETs are used in the ACV
and ACV + DCV Functions. The FETs are turned On
and Off by Comparators in the AC Converter. The
Comparators are controlled by the Range and Function
Control Logic, which in turn is controlled by the [n­
guard Logic. If a FET is suspected to be defective, make
sure the logic is good before replacing the FET. A FET
is normally Off with its gate at approximately - 1 4 V to
- 1 5 V and is On at zero volts. Go to Service Group B,
if the Inguard Logic is defective.
Fllllttil.
ACV
ACV
ACV
ACV
ACV+ OCV
ACV+ OCV
ACV+ OCV
ACV+ OCV
Note: 1 High, 0
""
SERVICE GROUP E
has the ACV and
information for the
Table a·E·" ACV Switch Closure Commends.
....
� :I: ... ....
"
:I: :>:: � :>::
1 V DOlO
1 0 V 0010
100 V DOlO
1 000 V DOlO
1 V DOlO
1 0 V
0010
100 V 0010
1 000 V 0010
Low
=
8-E-6. Similar to the FETs, the two relays used in the
Converter are also controlled by the Range and Func­
tion Control Logic. The only difference is that tran­
sistors, which are driven by Nand gates, turn the relays
On and Off.
B·E·7. SWITCH CLOSURE COMMAND TABLE.
+
8-E-8. Table 8-E-l lists the commands for the ACV and
ACV DCV Functions and Ranges. Use the table to
determine which FET or Relay is on or off for the AC
functions and ranges.
B·E·9. ACV AND ACV+OCV FAILURE ISOLATION.
8-E-IO. The 3456A has two AC Functions: ACV and
ACV + DCV. The ACV Function can only measure ac
voltages and the ACV + DCV Function can measure
both ac and dc voltages. Because of this, the functions
should be isolated from each other. Do the following:
a. Determine the failure.
b. If the failure is in the ACV Function and not the
ACV + DCV Function, go to Paragraph 8-E-38 for
troubleshooting.
c. If the failure shows up in both functions, but only
for ac inputs (e.g. the failure shows up with a I V ac in­
put and not with a corresponding ! V dc input), go to
Paragraph 8-E-38 for troubleshooting.
d. If the failure is in both functions and shows up
with an ac and dc input (e.g. the failure shows up with a
1 V ac input and a corresponding 1 V dc input), go to
Paragraph 8-E- ! 1 for troubleshooting.
Switch Clnllft COllllll u d •
> :::t :I: ....
... :::t
� :::
�agg
c
u
u « ..: « ....
.... 1: :>:: :>::
:>:: :I: :>:: :>:: 1: :I: :>::
... .
... .
01 1 1 1 000 0000
01 1 1 1 000 0010
01 1 1 1 000 0001
01 1 1 1000 001 1
01 1 1
1 000 0000
01 1 1 1 000 0010
01 1 1
1000 0001
01 1 1
1000 001 1
• •
:::t
1: % % %
:>:: % % %
1 000
1 000
1 000 0100
1 000
DOlO
1 000 0001
1 000 1 000
1 000 0100
1 000 0010
1 000 0001
Service
8-E-!