33
Service and Repair Manual
Model 900/950/990
With the aid of the Fault Finding chart (below) the source of any malfunction may be quickly identified and repaired.
REMEDY FAULT
AND RETEST
MOTOR
REVOLVES?
MACHINE
HAMMERS?
MACHINE
IDLES?
SUPPLY
OK?
PLUG FUSE
OK?
BRUSHES
OK?
CORD
OK?
SWITCH
OK?
ARMATURE FIELD INTERNAL
WIRING
SERVICE
MECHANISM
MODULE
WAS MOTOR
BURNT OUT?
MACHINE
OK
YES
NO NO
YES
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO
ON COMPLETION OF ASSEMBLY THE UNIT SHOULD BE FLASH TESTED AT
4000 VOLTS. THE UNIT SHOULD BE RUN PREFERABLY AT HALF STATED
VOLTAGE FOR 10 MINUTES TO ENSURE CORRECT BEDDING OF BRUSHES.
AFTER 10 MINUTES THE UNIT SHOULD BE RUN AT FULL STATED VOLTAGE.
POWER READINGS SHOULD BE CHECKED AGAINST THE PERFORMANCE
DATA.
With the breaker completely assembled and with the switch "ON" apply not more than 2000 volts
initially and then raise quickly to 4000 volts between the main casting and one of the pins of the
plug on the power supply cord.
LETHAL VOLTAGES PRESENT - DO NOT TOUCH PINS
The full voltage of 4000 volts should be maintained without breakdown or flashover for a few
seconds.
If, however, the armature has already been tested then it is better to remove the carbon brushes
before carrying out the test. This avoids over-stressing the armature insulation system for a second
time. In this case the test voltage must be applied between the main casting and each live pin of the
plug in succession.
FAILURE TO SWITCH THE MACHINE ON MAY CONCEAL A FAULT WHICH
WILL RESULT IN AN ELECTRIC SHOCK TO THE USER. ENSURE THAT THE
SWITCH IS ON BEFORE TESTING.
WARNING
WARNING
WARNING
FAULT FINDING
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