Read Sharp SD-AT50H (serv.man10) Service Manual online
off power from all the parts except for the circuit driving the
Power is cut off after “ER_AP02” is displayed.
Power is cut off after “FAN LOCK” is displayed.
V) (normal) .
The motor stops when it is above approx. 1 V.
If the voltage of pin 21 (FAN LOCK) on IC701 is not
between approx. 0.21 V and 0.9 V whilst the motor
rotation is controlled, it is judged as abnormal.
disconnection by output short-circuit of each
regulator may cause the parts or PCBs to burn
out and therefore do not disconnect the detection
line when the cause is not identified.
(Power supply can be detected with an
oscilloscope or like during approx. 0.5 seconds
after an abnormality is found. Note that the
detection would be difficult with a tester as the
voltage rises and falls rapidly.)
the stabilizing output of the regulator, and turn on the unit.
If the detected voltage is extremely lower than the voltage
on the circuit diagram (below approx. 1.5 V), the regulator
itself or the circuit is defective.
operation is still activated, QA100 ~ QA103, QA200 ~
QA203 or QA300 ~ QA303 on the 1-bit amplifier could be
defective (the detection circuit of the speaker output DC
BIA111 (1-bit amplifier main power supply connector). (No
sound is heard from the speaker.)
BIA111, QA413, QA414, QA415, QA410, QA411 or QA412
could be defective (the detection of power supply voltage).
pin 21 (FANLOCK) on IC701 terminal, and turn on the unit.
Connect the collector of Q822 to GND and make sure the
fan motor rotates properly. If not, check if the motor or fan
is obstructed and the motor itself is defective. If all the above
are fine and the voltage of pin 21 is below approx. 0.2 V with
the collector of Q822 connected to GND, check Q830, its
peripheral circuits or the connection of the fan motor. The
fan motor could be defective if the voltage of pin 21 exceeds
approx. 0.91 V right after connecting the collector of Q822
to GND and remains above approx. 0.91 V.