27
Models C706 & C707
Controls
Unusual Failu res of the X32326--SER
Power Board
The fault of interest is the catastrophic failure of the
tracks that form the current sensing loop for the beater
motor. These are the traces that lead from the beater
terminals to the current transformer . There were a
number of cases where these tracks were blown off the
circuit board. Dixson was made aware of this problem
in October 1997. At that time they reported seeing this
problem on 5 of the 7000 boards produced in 1997.
The corrective action they took was to increase the
size of the traces. This revision was made March 1998.
Based on their testing, Dixson has concluded that the
most reasonable cause of this failure is either a line to
line short or line to ground short. Under locked rotor
conditions, the beater motor overload opened before
the tracks failed.
Please be on the alert for this problem. If at all possible,
get the date code of the defective board and any other
pertinent information. The date code format is year ,
month, day. The date code is stamped on the Dixson
label. In light of the cause of the defect, the service
technician should be looking for a source of
intermittent shorts to line or ground.
The three terminals labeled BEATER and GND are
clearly marked on the power board, but if the GND wire
is exchanged with the BEATER wires upon
reinstallation when power is energized, it will blow the
tracks off the board.
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