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Troubleshooting - Sharp SM-SX1 Service Manual

1-bit amplifier
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SM-SX1/SX1W
• Power is not supplied.
Does AC100V stand between Pins 1 and 2 of the power
filter PWB connector CNP502?
Is any normal voltage output from the power PWB
B1503/CNS503?
Is 5V supplied to Pin 13 of the microcomputer IC907?
Is any oscillating waveform found at Pins 14 (OSC2) and
15 (OSC1)?
• If no sound is present at the analog or digital input
Are the speaker relays RLY201 and RLY202 switched?
Are they properly wired to the 1-bit amplifying unit?
(CNWAM1, CNWAM2, CNWAM3, CNWAM4)
Is voltage properly supplied to 1-bit amplifier? (CNP306)
Is voltage properly supplied to 1-bit amplifier? (CNP305)
Is any signal output from the connectors CNP303 and
CNP304 for 1-bit amplifier?
Check the inside of the 1-bit amplifying unit.

TROUBLESHOOTING

Yes
Yes
Yes
Yes
Yes
Yes
Yes
(LED904 does not come on and it does not sound.)
• Check the fuse F501.
• Check the parts on the power filter PWB.
No
• Check the wiring of the inlets SOC501 and CNS501.
• Check the output voltage (OYT terminal) of UNT501 and
No
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.)
• Check IC306 output.
• Check R391.
No
• Check X900.
No
• Check IC907.
(when power is supplied and LED904 is lit.)
• Check whether 12V is supplied to RLY201 and RLY202 or not.
No
(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.
• Check whether the proper voltage is output from the AC
No
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.
• Check -22V (around Q115 and Q114).
• Check 5V (around Q105 and Q106).
No
• Check reset 5V.
(Connection from Pin 21 of the microcomputer IC904.)
• Check CNS601A/B and main volume, VOL601.
No
• Check the IC107 output voltage which is supplied to drive
the relay.
• Check the relays RLY601 and RLY602 and drive circuit.
– 34 –

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