Diagnostic Testing and Troubleshooting
Introduction
5
5-3
5-1. Introduction
The Fluke 45 provides error code information and semi-modular design to aid in
troubleshooting. This chapter explains the error codes and describes procedures needed
to isolate a problem to a specific functional area. Finally, troubleshooting hints for each
functional area are presented.
But first, if the meter fails, check the fuses and replace as needed. If the problem
persists, verify that you are operating the meter correctly by reviewing the operating
instructions found in the User’s Manual.
WWarning
Opening the case may expose hazardous voltages. Always
disconnect the power cord and measuring inputs before
opening the case. And remember that repairs or servicing
should be performed only by qualified personnel.
Required equipment is listed in Chapter 4 of this manual.
Signal names followed by a ’*’ are active (asserted) low. Signal names not so marked are
active high.
5-2. Servicing Surface-Mount Assemblies
The 45 Dual Display Multimeter incorporates Surface-Mount Technology (SMT) for
printed circuit assemblies (pca’s). 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. It is not recommended that repair be attempted
based only on the information presented here.
Since sockets are seldom used with SMT, "shotgun" troubleshooting cannot be used; a
fault should be isolated to the component level before a part is replaced. Surface-mount
assemblies are probed from the component side. The probes should make contact only
with 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.
This Service Manual is a vital source for component locations and values. With limited
space on the circuit board, chip component locations are seldom labeled. Figures
provided in Chapter 6 of this manual provide this information. Also, remember that chip
components are not individually labeled; keep any new or removed component in a
labeled package.
Surface-mount components are removed and replaced by reflowing all the solder
connections at the same time. Special considerations are required.
• Use a solder tool with regulated hot air to melt the solder; there is no direct contact
between the tool and the component.
• Surface-mount assemblies require rework with wire solder rather than with solder
paste. A 0.025 inch diameter wire solder composed of 63% tin and 37% lead is
recommended. A 60/40 solder is also acceptable.
A good connection with SMT requires only enough solder to make a positive metallic
contact. Too much solder causes bridging, while too little solder can cause weak or open
solder joints. With SMT, the anchoring effect of the through-holes is missing; solder
provides the only means of mechanical fastening. Therefore, the pca must be especially
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