SM-SX1 (serv.man2). (including circuit diagrams and s) - Sharp Audio Service Manual (repair manual). Page 34

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No

Does AC100V stand between Pins 1 and 2 of the power
filter PWB connector CNP502?

(LED does not come on and it does not sound.)

• Check the fuse F501.
• Check the parts on the power filter PWB.
• Check the wiring of the inlets SOC501 and CNS501.

Yes

No

Yes

Is any normal voltage is output from the power PWB
B1503/CNS503?

• Check the output voltage (OYT terminal) of UNT501 and

UNT502.

• Check the parts (L504 to L511, F502, FS503 and R503 to

R506) on the power PWB.

• Check the 1-bit amplification unit.
   (Try to disconnect CNWAM4 and CNWAM3.)

No

Yes

Is 5V supplied to Pin 13 of the microcomputer IC907?

• Check IC306 output.
• Check R391.

No

Is any oscillating waveform found at Pins 14 (OSC2) and
15 (OSC1)?

• Check X900.
• Check IC907.

No

Yes

Are the speaker relays RLY201 and RLY202 switched?

(when power is supplied and LED is lit.)

• Check whether 12V is supplied to RLY201 and RLY202 or not.
  (Check the surroundings of Q201, Q202, R201 to R202.)
• Check whether Q203 and Q204 are on or not.
• Check the line Q203 and Q204 from Pin 41 of the
   microcomputer IC907.

Are they properly wired to the 1-bit amplifying unit?
(CNWAM1, CNWAM2, CNWAM3, CNWAM4)

No

Yes

Is voltage properly supplied to 1-bit amplifier? (CNP306)

• Check whether the proper voltage is output from the AC

input filter CNP502 or not.

• Check whether RLY303 is activated or not.
• Check whether Q303 is on or not.
• Check the line Q303 from Pin 42 of the microcomputer

IC907.

No

Yes

Is voltage properly supplied to 1-bit amplifier? (CNP305)

• Check -22V (around Q115 and Q114).
• Check 5V (around Q105 and Q106).
• Check reset 5V.
   (Connection from Pin 21 of the microcomputer IC904.)

No

Is any signal output from the connectors CNP303 and
CNP304 for 1-bit amplifier?

• Check CNS601A/B and main volume, VOL601.
• Check the IC107 output voltage which is supplied to drive

the relay.

• Check the relays RLY601 and RLY602 and drive circuit.

Yes

Check the inside of the 1-bit amplifying unit.