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Routing the Touchscreen Cables
The internal cables that carry the analog touchscreen signals are subject to
interference from various sources within the display. The routing of these cables
should avoid the following areas, listed in order of importance:
• flyback transformer-CRT (anode lead)
• anode lead-CRT
• inverter section of the power supply-Flat Panels only (most display power
supplies are switching power supplies, and the main DC to AC inversion
section produces most of the noise)
• yoke-CRT
• RGB video drive section of the display
• video input cable
• horizontal and vertical oscillator/drive sections-CRT (large caps)
Once acceptable cable positioning is determined, tie the cable down to avoid
movement during shipment. In addition to careful cable routing, other EMI
suppression techniques may be necessary to satisfy agency approval
requirements. Use ferrite beads or other radio frequency (RF) suppression
elements, additional shielding, and different grounding techniques as needed.
Also, attach all excess cable/service loops as close to the chassis as practical to
reduce noise emissions.
Reassembling
the Monitor
With the touchscreen mounted, and the cable routing and exterior interface
determined, the display must be reassembled. Reassembly is generally in
reverse order of disassembly. Beware of potential clearance problems between
the bell of the CRT and the electronics chassis, as shorts in this area can produce
catastrophic failures of the display. Also, if the inside surface of the back case is
painted with a conductive coating, watch for shorts between the CRT circuit
board and the rear of the back case, as these can also produce disastrous results.
When the electronics chassis is reinstalled, the CRT circuit board is usually
carried along with it. It is often advisable to have a second person assist you, to
insure that this circuit board and various other cables do not interfere with the
yoke or neck of the CRT. Safety glasses, gloves, heavy protective clothing, and
caution are strongly advised for all participants.