Model 8903B Service
CAUTION
Tip prwiirc?
on
the>
pud is
most
oiticul and is
totully
operator
dcpcwdcwt. Exccrsivo lip
prcssiirc will duniugc or deslroy
thc
bourd.
Do
no/
iisc
tin dcsoldcring hraid
or
.soIdcr
wicking
Icchniqiiec.
on
Hot
A
ir
Levth>d
board.%.
The melting point of soldcr in the plated through hole (PTH) is reached
in
2.5 seconds at
tip
temperature
of 600"to 750°F (315"to
400°C).
The recommended time for heat
to
be applied is
3
seconds.
Keep the solder sucker
clcan
and do not let the tip
of
the solder sucker hit the pad when removing solder.
Breaking the lead loose can damage the PTH. If the lead is attached
to
the PTH after the solder has been
removed, reheat the lead to remove it.
4.
When soldering or desoldering multilead components, do not consecutively apply heat to adjacent leads.
Distribute heat by skipping leads
or
crossing
to
opposite side of device.
8-16.
GENERAL TROUBLESHOOTING
Instrument problems usually fall into three general categories: operator errors, operation out of specification,
and catastrophic failures. The troubleshooting strategy is different for each category.
8-1
7.
Operator Errors
Apparent failures sometimes can result
from
using the instrument outside of its range. Usually, the instrument
can sense the condition and will display an error message. At other times it cannot, such as when it attempts
to measure signals with frequencies higher than
100
kHz. Consult the
SpccficationJ
table (Table
1-1)
and the
Detailed Operating Instructions
in Section
3
for more detailed information.
8-1
8.
Operation Out
of
Specification
The specifications are listed in Table
1-1.
Performance tests that can be used
to
verify the specifications are
found
in
Section
4.
If instrument performance is only slightly out of limits, it can sometimes be corrected by
an adjustment. The procedures for adjustments are in Section 5. References listed for each adjustment indicate
which service sheet
to
consult when the adjustment procedure fails. In general, however,
it
is also
a
good
practice to perform the troubleshooting checks
on
Service Sheet BDI, since they take
only
a few minutes and
reveal much information.
8-1
9.
Catastrophic Failures
Begin troubleshooting catastrophic failures by performing the troubleshooting checks on Service Sheet
BD
1.
The simple procedures there take only a few minutes and will quickly differentiate a control (digital) problem
from a hardware (analog) problem. The checks then give cross-references to the detailed block diagrams (Service
Sheets BD2 to BD5) or
to
a schematic.
The troubleshooting information found on all service sheets consists of a series
of
performance checks. The
purpose of the checks is not
to
identify which circuit
or
component has failed but rather to verify whether
or
not the assembly or circuit is operating correctly. Information on the possible cause of failure is given in the
form of hints whenever they can be given reliably. The limits given in the troubleshooting checks are rather
8-4.1
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