Husqvarna DM 650 Workshop Manual page 21

IMPORTANT: No measurements should or must be carried out with the machine connected to a power source!
TROUBLESHOOTING
Tools
Multimeter
A multimeter is needed for most of the tests in order to measure
resistance (ohm) and inductance (H = Henry). The multimeter's
connection test with a buzzer is used to check switches, cables,
contacts, etc. (The Husqvarna range of tools includes an efficient
multimeter; see page 25.)
Insulation and continuity tester
The motor works with a voltage of just over 500 V AC. Even if
simple measurement with a multimeter shows that the motor is
demonstrating no insulation faults at stator windings or in connec-
ted cabling, it is not possible to rule out faults in these. Defective
insulation can cause arcing at high voltages. This can be tested
using an insulation tester. Megger and Fluke are just two examples
of common makes.
Insulation is conveniently measured at 1,000 V over 3 seconds
with a maximum of 5 mA.
Note that connected test cables and test probes must be designed
for 1,000 V or more.
Carefully read the instrument's operators manual for use!
Tachometer and screwdriver
The strength of the rotor's magnetic field is tested by rotating
the motor to 1,000 rpm and measuring the voltage it emits at this
speed. A simple tachometer is needed for this: an optical laser
seeker is suggested. The easiest way to achieve rotation is to use a
screwdriver.
Rules of procedure for troubleshooting
Defective HF unit or drilling machine?
When troubleshooting, it is important to remember that the fault
may be in either the drilling machine DM650 or the PP65 unit. If
you have access to another working PP65 and machine, these can
be used in order to identify the faulty unit.
If you have no other PP65 or machine to hand, the easiest way
to go about troubleshooting is to start with the drilling machine,
as this is made up of relatively few components.
Troubleshooting DM650
The troubleshooting order can often be decided in each individual
case depending on the symptoms, signs of external damage,
operating conditions, number of hours of operation, etc.
The motor will not start
If the history of the drilling machine is not known and there are no
further external signs of damage visible, the components of the
machine must be tested. There are few components to test:
– Cabling, between the HF unit and the drilling machine
– The motor unit with built-in thermistor
– Switches
– The display unit
Remove the display unit
For all checks, it is necessary to remove the drilling machine's
display unit as illustrated in order to make the electrical couplers
accessible.
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