User manual

Table Of Contents
Section 6: Customer Service 6-5
Moseley SL9003Q 602-12016 Revision G
Field Repair Techniques
If an integrated circuit is suspect, carefully remove the original and install the new one,
observing polarity. Installing an IC backward may damage not only the component itself, but the
surrounding circuitry as well. ICs occasionally exhibit temperature-sensitive characteristics. If a
device operates intermittently, or appears to drift, rapidly cooling the component with a
cryogenic spray may aid in identifying the problem.
If a soldered component must be replaced, do the following:
Use a 40W maximum soldering iron with an 1/8-inch maximum tip. Do not use a soldering
gun. Excessive heat can damage components and the printed circuit. Surface mount
devices are especially heat sensitive, and require a lower power soldering iron. If you are
not experienced with surface mount components, we suggest that you do not learn on
critical equipment.
Remove the solder from the component leads and the printed circuit pads. Solder wicking
braid or a vacuum de-solderer is useful for this. Gently loosen the component leads and
extract the component from the board.
Form the leads of the replacement component to fit easily into the circuit board pattern.
Solder each lead of the component to the bottom side of the board, using a good brand of
rosin-core solder. We recommend not using water soluble flux, particularly in RF portions of
the circuit. The solder should flow through the hole and form a fillet on both sides. Fillets
should be smooth and shiny, but do not overheat the component trying to obtain this result.
Trim the leads of the replacement component close to the solder on the pad side of the
printed circuit board with a pair of diagonal cutters.
Completely remove all residual flux with a cotton swab moistened with flux cleaner.
For long term quality, inspect each solder joint – top and bottom – under a magnifier and
rework solder joints to meet industry standards. Inspect the adjacent components soldered
by the Moseley Associates production line for an example of high reliability soldering.