Mitsubishi SL2U Service Manual page 4

Power source system 1
The product does not
enter the stand-by mode.
Has the FUSE (F901)
blown?
PCB-INLET
NO
Is the thermal
protector
conducting?
YES
Is the lead wire
to the RB
connector cut?
NO
Is the pin No. 8
of the SF
connector 5V?
PCB-MAIN
YES
Replace the PCB-
MAIN and check if the
product enters the
stand-by mode.
YES
Malfunction of PCB-MAIN.
Using the Terminal Shield as GND is allowed when checking the voltage waveform or terminal voltage on the secondary side.
(Don't use a heat dissipation board as GND.)
LED does't illuminate.
Check the STBY5.
YES
NO
Replace the lead wire.
YES
Remove the
NO
SF connector
from the PCB-
MAIN.
NO
Malfunction of MEMBRANE
switch.
Replace MEMBRANE switch.
Check the failure on the PCB-
POWER, then replace the parts.
Reset the thermal protector
and check the dust on the
filter.
PCB-POWER
Is the pin No. 9
of the RF
connector 5V?
YES
Replace the PCB-
MAIN. Check that the
product enters the
stand-by mode.
NO
Replace the PCB-
TERMINAL. Check that
the product enters the
stand-by mode.
NO
Replace the PCB-
AUDIO. Check that the
product enters the
stand-by mode.
NO
Replace the PCB-
PREAMP. Check that the
product enters the stand-
by mode.
NO
Malfunction of MEMBRANE
switch. Replace MEMBRANE
switch.
- 2 -
thermal protector : on the lamp box
Check the circuit around
NO IC950, IC951 and PC950,
then replace the parts.
IC950 : Primary side SW-IC
PC950 : Photo coupler for feedback
IC951 : Shunt regulator for feedback
Z954, Z955 : Circuit protector
YES
Malfunction of the PCB-MAIN.
Malfunction of the PCB-TERMINAL.
YES
YES
Malfunction of the PCB-AUDIO.
Malfunction of the PCB-PREAMP.
YES