Philips DVD-712, Service Manual

Page: 40 / 61

Circuit Descriptions And List Of Abbreviations
GB 56 DVD712-722 9.
9.1.4 Pin Function Description
Figure 9-2
9.1.5 Pin Connection
Figure 9-3
9.1.6 Output Voltages
• +12V ( For Display board, Monoboard, A/V board )
created via D6241, C2240, L5240, C2232 (This voltage
is also present during standby)
• +5V_ stdby ( For Display board, Standby PCB,
Monoboard ) created from +6V via R3233 and D6233
(This voltage is also present during standby)
• +6V_stdby ( Reserve ) created from D6230, C2230,
L5231 (This voltage is also present during standby)
• +5V ( For Monoboard, A/V board ) derive from +6V stdby
via Mosfet 7238, C2239 and it will be switch off via
R3235, T7235 during Standby.
• -5V ( For Monoboard, A/V board ) created from D6250,
C2250, C2259, L5222, R3259, T7255 regulator circuit
and will switch off via R3258, T7257 during standby
(control signal Standby is HIGH)
• 3V3 ( For Monoboard, A/V board ) The 3V3 power
supply is regulated by the control loop comprising of
7201, 7131 and 7145 of the switch mode PSU. This
voltage is also present during standby
• -40V ( For Display board ) created via D6261,R3260,
L5260, C2260 This will not be present during standby
9.2 Control Circuitry
9.2.1 Mains Input Circuit
The mains voltage is rectified by bridge rectifier (D6118 to
D6121) and filter by C2121. The DC voltage across C2121is
the DC input voltage ,approximately 300V, is the DC input to
pin 1 of transformer T5131.The mains input also consists of
a lighting protection R3120.
9.2.2 Start-Up And Takeover Circuitry
The start-up circuitry consist R3123, R3134, R3111, D6129,
C2134 and with the mains voltage input, the C2134 will
charge via R3123 and R3134. When the voltage at pin 7 of
IC7145 reaches the start-up threshold of min 14.5V,
IC7145 will start-up and the control circuit start to operate.
After start-up, the max sinking current of 17mA is required by
IC7145 which is not able to be delivered by the start-up
circuitry, so the takeover circuitry must be present.
If the takeover circuit does not occurred, the supply voltage
at pin 7 will decrease gradually till it reaches the IC7145
minimal operating voltage of 8.5Vand the IC will switch off.
The whole operation cycle will repeat itself with audible
hiccup sound if takeover is not present.
The takeover circuit comprises of D6133, R3135, l5135,
C2134. During the control circuit start-up, the voltage across
winding pin 7 and 9 will gradually built up and charged C2134
CL06532096_011.eps
060700
CL06532096_012.eps
060700