Cable Shorts Test - Printronix P5000 Maintenance Manual

Chapter 4

Cable Shorts Test

Cable Shorts Test

This test determines if a cable has a short to ground or a pin-to-pin short (also
called a wire-to-wire short). Such shorts can be caused by cables resting on
or moving across sharp edges. The edges over time can wear away the
plastic shielding of the cable, exposing the copper wire inside. A short occurs
when the exposed wire touches another metal surface or conductor.
This procedure tests only the cables listed below that can be disconnected at
both ends:
•
Intermediate cables of devices in the Main Wire Harness Test Tables:
Card Cage Fan
Left Ribbon Motor
Right Ribbon Motor
Exhaust Fan (in cabinet models)
Magnetic Pick-up Unit (MPU)
•
Shuttle Motor Intermediate Cable
•
Hammer Bank Power and Logic Intermediate Cables
•
Control Panel Assembly Intermediate Cable
•
Power Stacker Logic and Power (Intermediate) Cables
The Procedure:
1. Prepare the printer for maintenance (page 132).
2. Disconnect the cable to be tested at both ends, but leave the cable
routing as it was before you started this procedure.
3. Set your Ohmmeter to the 10K Ohm scale or the scale closest to 10K
Ohms.
4. Hold the two meter leads apart from each other (not touching anything)
and note how your meter indicates an open circuit. For example, some
meters read OL (Over Load), -1, flashing display, infinite resistance, etc.
Record this indication for later reference.
Check for shorts to ground:
5. Attach the common meter lead (usually black) to a ground point on the
printer (e.g., a bolt head on the shuttle casting).
6. Touch the positive meter lead (usually red) to another ground point and
verify continuity. (Continuity is a low resistance reading of less than 1
Ohm.)
IMPORTANT
When making continuity checks, touch the meter leads to the test points
for at least 2 to 3 seconds so your meter has time to display correctly.
7. At one end of the cable, touch one of the pins with the positive (usually
red) meter lead while the common lead (usually black) is still touching a
ground point.
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