Note on Removing the POWER SUPPLY Unit from the Chassis
and Method for Resetting Standby Power Latchup
For 3-5 minutes after the unit is turned off, residual electric charge remains in the C310 capacitor on the POWER SUPPLY
Unit. Before removing the POWER SUPPLY Unit from the chassis, be sure to confirm that residual charge inside the POWER
SUPPLY Unit has become sufficiently low. (Without forced discharge, residual charge that remains after 3-5 minutes will fall to
one-tenth or less, which is still about 20 V. Therefore, even after the POWER SUPPLY Unit is removed, it is recommended to
perform forced discharge on the POWER SUPPLY Unit, as shown below.)
For quick removal of residual charge, forced discharge is recommended, using two 220 ohm/10 W resistors (440 ohm/20 W).
How to remove the POWER SUPPLY Unit
1. Make sure that the AC power cord is unplugged. Using a tester, check the voltage between the + terminal of RC101 bridge
diode and Q301 radiator (equivalent to the voltage between two electrodes of C310).
2. Let the unit sit for more than 5 minutes until the voltage equivalent to that between two electrodes of C310 falls to under 20 V.
3. After checking that the voltage is under 20 V, disconnect the connectors of the POWER SUPPLY Unit and remove the POWER
4. Using two resistors mentioned above, completely discharge residual charge from C310.
How to reset Standby power latchup
(In a case where the protection against Standby power excess voltage is activated)
1. After removing the causes of the malfunction, short-circuit between the JW1 and JW2 jumpers.
2. If the POWER SUPPLY Unit functions properly, after opening the above jumpers, the unit starts up.
After checking that the voltage at the measurement points
(equivalent to the voltage between two electrodes of C310)
is under 20 V, remove the POWER SUPPLY Unit.
Then, completely discharge residual charge, using resistors.
To forcibly reset latchup of STBY3.4 V, short-circuit between JW1 and
JW2 (near C603), using a flathead screwdriver or similar object.
If the causes of the malfunction are removed, after opening the jumpers, the unit starts up.
RC101 + terminal
Site where power-down is detected
(Pin 3 of CN801)