Chamberlain JDC - Page 46

46
Troubleshooting (continued)
Symptom Possible Causes Diagnosis Resolution
Powerhead main
board is o
(no LEDs are lit or
blinking)
(continued)
Faulty EMI lter
board
Verify EMI lter board:
Perform this test only after rst
verifying input AC voltage.
Measure AC voltage at EMI lter
board output. Measure from brown
wire to blue wire. [todo: check wire
colors for 480V] Verify voltage is
within specications.
If input voltage is within
specication but output voltage is
outside specications or is absent,
replace the EMI lter board.
Faulty Transformer Verify Transformer:
Perform this test only after rst
verifying the EMI lter board.
Disconnect transformer output
winding from rectier(s) and
measure the AC voltage across
transformer output winding.
Voltage should be between 22
and 35 volts AC. If voltage is out of
range, see resolution.
If voltage is too high or too low,
check that 120V/240V input voltage
selection is correct.
If voltage is absent: transformer has
thermal protection to automatically
disconnect input voltage if the
transformer overheats. Allow
transformer to cool if it is hot, and
then re-test.
If transformer is cool and voltage is
still absent, replace the transformer.
Faulty wiring or
connections
Inspect all connections and wiring
from EMI lter board, transformer,
rectiers, and DC IN terminals on
the main board. Ensure there are no
loose connections, cut wires, broken
insulation, etc.
Verify wiring matches wiring
diagram.
Correct any issues found with wiring
or connections.
Faulty Rectier Verify Rectier:
If the transformer and all wiring is
veried but DC voltage is still not
present at the main board DC IN
terminals, the rectiers are most
likely faulty.
If an electrical meter with a diode
test function is available, each of
the 4 diodes internal to the bridge
rectiers may be checked using the
diode check functionality:
1) check each diode in the forward
direction and verify they conduct
with ~ 1V drop or less
2) check each diode in the reverse
direction and verify they do not
conduct (meter will read the same as
disconnected leads)
Replace faulty rectier(s).
Rectier mounting screws must
be tight enough to ensure good
thermal contact with the chassis
through the thermal interface
pad. However, the rectier screw
must not be too tight or it could be
damaged. [torque spec here, even?]
Interface between the rectier and
the chassis should be clean of any
foreign substances before a new
rectier is installed.
Short or overload
in device
connected to main
board
Turn o power and disconnect
batteries from main board.
Disconnect all cabling from main
board except for main power.
Restore power and verify LEDs light.
Reconnect wiring to main board one
device at a time testing to see if any
device causes the main board to fail
to light LEDs.
If any device is found to cause an
issue, the device may be faulty and
should be repaired or replaced as
necessary.