Locating bad crimps

For the cable installer, crimping modular plugs is an important task. If this technique is done improperly, it can lead to hours of frustration trying to locate open and intermittent lines.

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Al Contarino, L-Com Inc.

Problem

For the cable installer, crimping modular plugs is an important task. If this technique is done improperly, it can lead to hours of frustration trying to locate open and intermittent lines.

Solution

To verify that plugs were crimped correctly, first make a visual inspection; then, if necessary, check the cable with electronic test equipment.

Procedure

1) For the visual inspection, use a magnifier, loupe or microscope because flaws can be difficult to see with the naked eye.

2) Look at the plug from the front and check that the wires were trimmed with a sharp instrument to ensure no strands are sticking out past the insulation on the wires.

3) Check that the main strain relief is making tight contact with the cable jacket. All strain should be on the cable jacket, not on the wires.

4) If a secondary strain relief was used, make sure it was crimped properly and is seated on top of the wires.

5) With a magnification device, view the surface of all contacts. They should all be aligned parallel to each other, with no plastic burrs showing in the contact areas. If poor-quality tools or plugs were used, a burr of plastic can build up on the two outermost pins--pins 1 and 8 of an RJ-45 connector--during the crimping cycle. This burr will prevent proper contact with the mating jack.

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Plastic burr built up on pin 1 of an RJ-45 connector during the crimping cycle will prevent proper contact with the mating jack.

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