Table of Contents
Model 3456A
B·A· 1 . GENERAL.
8-A-2. This Service Group has the troubleshooting in
formation for the 3456A's Outguard. Choose the cor
rect troubleshooting information by referring to the
3456A's failures and failure symptoms, given in the Ser
vice Group.
B·A·3. PRHROUBLESHOOTlNG CHECKS.
8-A-4. Before
troubleshooting
Outguard Failure, check the following:
a. Check the Outguard Power supply.
c. Check the clock waveforms (both phases) at
A4UI4, pin 13 and 15.
B·A·5. OUTGUARO FAILURES AND TROUBLESHOOTING.
8·A·8. Turn·On Feilure.
8-A·7 . Before troubleshooting for a Turn·On Failure,
check the following:
a. Make sure the Data Bus Break (A4ES) is making
good comact. If the pins are bent, the Data Line
Signatures may be good but the instrument may be in
operative.
b. Make sure the Test Jumpers (A4J9, JIO, J I 2 and
J 1 1) are in the "RUN" position. The 3456A will not
turn-on, if they are in a different position.
8-A-8. A Turn-On Failure shows up when the 3456A's
Data Lines (DO to D7) are bad. Symptoms for this type
of failure are:
a. The display is dead or inoperative. An inoperative
display may partly or fully show a number which may
jump around or is locked up. If dashes (- - . - - -) are
displayed, the 3456A does not have a Turn·On Failure.
an
It is most likely
Isolation Logic or Inguard Failure
(go to Paragraph 8-A-34 for troubleshooting).
b. Keyboard is dead andlor does not respond (by
pressing keys).
c. HP-lB is inoperative, although it may not be
necessary to check for an HP-JB failure if the previous
symptoms were noted.
8-A·9. The failure is present, if all of these symptoms
are true. In other words, if only a display is inoperative
and the keyboard is good, it is not a Turn-On Failure. In
that case troubleshoot the display. A good practice is to
troubleshoot for a turn-on failure if the 3456A is corn-
SERVICE GROUP A
the
3456A
for
an
pletely locked-up.
Also
troubleshooting
procedure
unusual symptoms.
8-A-IO. Since the Data Lines (DO to D7) are the most
likely cause of a turn-on failure, check the signatures of
the lines. Do the following:
a. Turn the 3456A Off.
b. Remove the Data Lines Break A4E5 from its
socket.
c. Move A4J9 and A4JI2 to their respective "ROM
SA" position.
d. Connect and set the Signature
follows:
Start:
A4TP3-A
Stop:
A4TP3-B
Clock:
A4TP3-C
Hold:
Self·Test:
Gnd:
Ground Pin (next to A4C I I )
e . Turn the 3456A On and read the Data Line
Signatures as given in Table 8·A-I.
8-A· I l . If any or all signatures are bad or noisy, go to
Flowchart A, Figure 8-A-I, for troubleshooting. If the
Signatures are good, the failure is most likely in the
RAM circuitry (RAMs, RAM Select, etc.) or Strobe
Decoders (A4U 17, Ul9, and associated circuitry). Go to
Flowchart B, Figure 8-A-2, for troubleshooting. If SA
does not work at all or the signatures are locked-up
(same signatures), troubleshoot the processor circuitry
(see Paragraph 8·A-27).
8·'·12. Inop.rltive DilpllY.
8·A-13. All the digits, except for the most significant
digit, first decimal point, and both polarity indicators,
are controlled by A4U29. An inoperative display is
when:
a. The digits are missing one or more segment.
b. One or more digit is not lit.
c. One or more digit (and/or) segment is always lit.
8-A-14. Since the most significant digit, first decimal
point, and both polarity indicators are controlled by
A4U30, a failure of these is considered an Inoperative
Annunciator (see Paragraph 8-A·l6). For a Combined
Annunciator and Display failure use Paragraph 8-A-2 1 .
Service
use the Turn-On Failure
for
failures
that
show
Analyzer as
( '- )
( ,- )
( '- )
Out
Out
8-A-1 / 8-A-2
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Troubleshooting
