FUSE & BRIDGE DIODE
Check and replace F901, BD901, TH901, TH903 on SMPS board.- Check if the fuse F901 is open or short-circuit.
- Check if the bridge diode DB901 is short-circuits by over current with a digital multi meter.
- Check if the NTC thermistor TH901 and TH902 is normal or open.
- Check the Anode-Cathode Voltage of D951 with a digital multi-meter, it is normally 0.2 ~ 0.3 V. => If it doesn’t have any voltage, it’s destroyed. Replace it with a new one.
- Check if ZD951 is short-circuits. => If it is short-circuit, and then replace it with a new one.
WHEN POWER ON, SET DO NOT BOOT
- Check the 3.7VA to CN102, CN103, and CN104 in standby mode. => If there is no 3.7 VA, check the SMPS.
- Check 5.6 V, 12 VA, FL+, FL- and 32 V when power on the set. If the set doesn’t work regardless of what the KEY1 changes high to low while pressing the power button. X100 and X101 work normally but, if you cannot power on the set, replace the IC101 with a new one on the main board.
VFD IS NOT DISPLAYS
- Check if 32 V, FL+ and FL- are output from SMPS to VFD via the MAIN board.
- Check if the IC101 outputs VFD_RST, VFD_CLK, VFD_STB, and VFD_STB to the FRONT board.
- Check if the VFD grid current amplifier circuit (Q301, Q303, Q304) on the FRONT board. Check the drive signal to the transistor’s base.
- If the control signals from VFD (TP302, TP303, TP304) aren’t output; replace VFD with a new one. If the transistor doesn’t work, replace it.
MD DO NOT WORK
- When no sound output in the CD function, you cannot listen to music reading data from a CD disc if the servo-motors in MD don’t work. This step is for checking the SPINDLE MOTOR among them.
- SPINDLE MOTOR: check and replace IC407, IC408 on MAIN board.
- Check the SPDO signal from Pin16 of IC407. If no signal, check 3.3V(RF) and X402.
- Check the SP- & SP+ from IC408 to CN405 for driving Spindle motor. It is about 3.6 Vp-p. If no signal, check +1.8 V and +5 V for IC408.
- Check if the FFC cable is solidly connected between CN405 and MD.
- Check the MD. If the spindle motor is sort-circuit or has any trouble, it cannot rotate CD discs. Check the function after changing another MD.
