Welch Allyn 4802D - Symptoms and Solutions

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NOTE: Ohmmeters will not indicate a change in resistance of the load cell transducer when weights are applied to scale. This
is due to the extremely small change in resistance of the strain gauges employed (<1 ohm) and the fact that the bridge
configuration presents a constant value of resistance when measured from its terminals.
Symptoms and Solutions
Symptom
Possible Cause
Corrective Action
Scale Does not turn on
Dead Batteries
“D” Cell
Try operating the scale in both power modes; AC &
Battery. If it functions normally when using AC power
replace all 6 D cell Batteries.
Damaged AC Adapter
Use a voltmeter or a multimeter to check continuity of
the adapter. Replace if needed.
Display Board/Mainboard
Repair or Replace.
Cracked Battery Holder
Replace the Battery Holder Assembly.
Load Beam/Calibration
(OHM out Load Cells) See Calibration procedure this
Service Manual.
------------- on display
Out of calibration
See calibration instruction.
Bad Load Beam
Side to side platform test using 10KG certified weight
 Apply weight evenly on the center of the scale. Press
“REWEIGH” two times and record your weight
reading each time.
 Remove weight from center and apply weight on
each side one at a time and Press “REWEIGH” two
times and record weight reading each time.
Examine your readings
Plot readings and they should be within ±0.4 lb./±0.2
kg from center reading.
The side that reads differently from all others is the
problem area. Repeat corner test if need be. Look for
obstructions and/or replace the Load Beam if necessary.
Scale not weighing correctly,
scale broken, drifting
Cable
Check Continuity of the Cable and if bad replace.
Display Board
Repair or Replace.
Main Board
Repair or Replace.
Cradle Assembly
Replace.
Cracked broken Cradle Assembly
Cradle Assembly
Replace.