Power Supply Block
The power supply is on a single board located to the left of the DVD mechanism. This board contains both the standby and the main power supply. The input line filter L101 and the board connectors are the only parts that are not available.
Standby Power Supply
This power supply produces Ever 5V as long as AC is present. Ever 5V is supplied to interface IC201 (MB85 board) and the mute transistors (AU212 board). The standby power supply consists of an oscillator and an error regulator. The oscillator consists of switch Q121 and a control transistor Q122. The oscillator output is applied to T102. T102’s secondary is rectified to output Ever 5V.
Regulation
The Ever 5V voltage regulation circuit uses:
·IC202 – error detector
·PC121 – photocoupler
·Q122 – control transistor.
IC202 samples the Ever 5V output and produces a correction voltage. Photocoupler PC121 passes the error voltage from the cold ground cir- cuit to the hot ground side circuit. The control transistor Q122 receives the error voltage and uses it to alter the base bias of switch Q121. The change in bias alters the off time of the oscillator signal. This changes the oscillator frequency. The changes in frequency affect the efficiency of the transformer, which regulates the Ever 5V.
Main Power Supply
The main power supply works similarly to the standby supply except the main supply is switched, handles more power and has multiple secondar- ies.
The main power supply is switched ON by PCONT from the Interface IC on the FR148 board. A high at PCONT enables switch Q101 to begin oscillating. Transformer T101 produces several output voltages that are rectified into DC for the remainder of the DVD unit.
11
When a shorted spindle motor driver IC802 loaded the unfused +12V supply line, the main oscillator quit. The oscillator worked again when the short was removed.
Regulation
The 3.3Vdc output is used to regulate the main power supply. Error detector IC201 receives the 3.3Vdc and produces a correction voltage. If the input voltage increases, the error detector output decreases. The PC101 photocoupler passes the correction signal to the control transistor Q102. Q102 adjusts the off time of the oscillator signal to correct the 3.3Vdc output the secondary. If the DVD power consumption is normal, the remainder of the T101 outputs will be correct.
Power Consumption
The current along each supply line was measured in both the idle and the DVD disc playback mode.
Model
Supply line | Part replaced | Current | |
| by Ammeter |
|
|
| Idle | Disc PB | |
|
| ||
|
|
|
|
Ever 5V | L205 | 30ma (set off) | 77mA (set on ) |
|
|
|
|
+12V partial | PS201 | 196mA | 198mA |
|
|
|
|
+12V total | L201 | 236mA | |
|
|
|
|
+5V | PS202 | 281mA | 305mA |
|
|
|
|
+3.3V | PS203 * | 894mA | 950mA |
|
|
|
|
PS204 | 129mA | 130mA | |
|
|
|
|
*Use short ammeter leads or the unit will not PB the disc and the display will not come on. The PS203 current without the display will only be 580mA.
Oscillator Frequencies
Power Supply Oscillator Frequencies
Power Supply | Set Off | Set On (stop mode) |
|
|
|
Standby (Q121/D) | 57.45kHz | 49.65kHz |
|
|
|
Main (Q101/C) | 0 | 101.2kHz |
|
|
|