Midland 70-1341, Service Manual

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SERVICING
70-1341/1344/1441/1444
REPLACING COMPONENTS WITH FEED-THROUGH LEADS
Exercise extreme care when replacing components with leads that feed through a PC board. The copper plating on
both sides of the printed circuit board and inside component lead holes easily separates and tears from the PC
board when heated.
Use a solder suction tool or braided desoldering-wick to remove solder from component leads, one at a time. Solder
must be removed carefully and thoroughly so that the IC can be pulled without resistance. After removing as much
solder as possible, use a dental pick or straight-pin to break the leads loose from the inside of the cleaned-out hole.
Cutting the defective components away from its leads first makes removing the leads and solder easier.
Before installing a new component, remove all solder from lead holes and make sure the device is oriented properly.
Always inspect old part leads for any feed-through plating rings that may have been pulled out of holes. The plating
may have completed a circuit. If so, make sure the corresponding lead of the new component is soldered to plating
runners on both sides of PC board as shown below.
FEED-THROUGH PLATING
PC BOARD
SOLDER SIDE PLATING RUNNER
THAT WAS CONNECTED TO
COMPONENT SIDE RUNNER BY
TORN-OUT HOLE PLATING.
TORN-OUT HOLE PLATING
NEW PART
OLD PART
COMPONENT SIDE PLATING
RUNNER. SOLDER
COMPONENT LEAD TO BOTH
THIS RUNNER AND SOLDER
SIDE RUNNER
Figure 4 – 6
4 - 6