Tecnetics Industries Tecweigh 20, Operation Manual

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Display failure…
There are two display failure scenarios: it does not light up at all, or it does light up but is acting
abnormally.
If it does not light up at all, first observe the green and red L ight E mitting D iodes (LED)s on the
WP20 printed circuit board (PCB). The green LED indicates sufficient power to the PCB and the
red LED indicates PCB failure. If the green LED is off or the red LED is on, verify that the DC
power supply is working properly as follows: On PCB model MP400 the DC power supply
converts the incoming 100-240 VAC to +30 VDC. Verify that the input voltage is at least 100
VAC and that there is +30 VDC at the power supply output (terminals 10 (-) and 29 (+)). Also
verify that the ribbon cable between the PCB and the display is installed correctly and is intact
If the display lights up but portions of it appear vacant or flash uncontrollably, it is likely that the
ribbon cable that connects the display board to the printed circuit board is damaged, or the
display board itself is damaged.
If any of these conditions are found to exist, or the problem cannot be pinpointed, contact the
Tecweigh Service Department (Section 2.01) for assistance.
Scale communications failure…
During normal operation a yellow LED on the WP20 printed circuit board (PCB) blinks every
1/5
th
second, indicating that communications with the SC300 or SC400 signal conditioner (SC)
at the scale is normal. If the yellow LED is off, or if it only blinks sporadically, verify that there
is +30 VDC across terminals 10 (-) and 29 (+) on the PCB. This is also the DC power for the SC
at the scale.
If +30 VDC does not exist across those terminals, disconnect the incoming power and check for
continuity across self resetting fuse F1 on the PCB. F1 is a tiny white rectangle located at the
very bottom of the PCB and just right of center. If continuity does not exist, contact the
Tecweigh Service Department (Section 2.01) for assisstance.
If +30 VDC is present, next verify that there is also +30 VDC at the SC (terminals 10 (-) and 29
(+)), if not, replace the cable between the WP20 and the SC.
If +30 VDC does exist at the SC, check the LEDs on the SC. The green LED indicates sufficient
power to the PCB, the red LED indicates insufficient power or PCB failure. As on the WP20
PCB, the yellow LED blinks every 1/5
th
second during normal operation on the SC’s. If it is not
blinking and +30 VDC exists, replacement of the SC is indicated. Contact the Tecweigh Service
or Parts Departments (Section 2.01) for assistance.
Other electrical problems…
Electrical “noise” from external electrical equipment such as variable frequency drives (VFD)s
and/or large motors can interfere with WP20 and signal conditioner (SC) operation. The
following are things that can be done to help prevent this problem:
•
Assure that the WP20 is on its own electrical circuit and verify that terminal G is earth
grounded.
•
Use dual twisted pair shielded cable from the WP20 to the SC. Belden #1063A is
recommended (See section 4.01.1).
•
Connect shield wires to the WP20 only, not to the SC.
•
Do not mount the scale or the WP20 near equipment that is a source of electrical
“noise”, or remove the “noise” source as much as is practical. This includes, but is not
limited to, motors, VFDs, SCRs, and high voltage power electrical cabling.