Troubleshooting; Surface Mount Assemblies - Fluke 76 Service

76
Service
R21 (ADJUST FOR
3.500V DC ± 0.001)

Troubleshooting

The procedures provided in these paragraphs will help isolate problems with the meter. In
these procedures, the meters are referred to as the unit under test (UUT).
When troubleshooting the Fluke 76 meter, use the precautions listed on the "Static
Awareness Sheet" to prevent damage from static discharge.

Surface Mount Assemblies

The 76 multimeter incorporates surface-mount technology (SMT) on the printed circuit
assembly (pca). Surface-mount components are much smaller than their predecessors,
with leads soldered directly to the surface of a circuit board; no plated through-holes are
used. Unique servicing, troubleshooting, and repair techniques are required to support
this technology. The information offered in the following paragraphs serves only as an
introduction to SMT. We do not recommend that you attempt a repair based only on the
information presented here.
Since sockets are seldom used with SMT, "shotgun" troubleshooting cannot be used;
isolate a fault to the component level before replacing a part. Surface-mount assemblies
are probed from the component side. The probes should contact only the pads in front of
the component leads. With the close spacing involved, ordinary test probes can easily
short two adjacent pins on an SMT IC.
Due to the limited space on the surface of the circuit board, component locations are not
labeled. Therefore, this service manual is a vital source for component locations and
values. Figures provided in Section 5 of this manual provide component location
information. Also, remember that SMT components are not individually labeled; keep
any new or removed component in a labeled package.
3-14
Figure 3-5. Calibration Adjustment Points
R34 (ADJUST FOR
3.500V AC ± 0.002)
l10f.eps
3-23.
3-24.