Marantz MAR775, MAR770, DR-6000 service manual Circuit description of P816

Page 26

Circuit description of P816

Input circuit

The input circuit consists of a lightning protection circuit and an EMI filter.

The lightning protection comprises R819.

The EMI filter is formed by C820, L820, C825 and C826. It prevents inflow of noise into the mains.

Primary rectifier/smoothing

The AC input is rectified by rectifier bridge D802 and smoothed into C821. The voltage over C821 is approximately 300V.

It can vary from 100V to 390V.

Start up circuit and Vcc supply

This circuit is formed by R823, R834, C829, D828, R829, R811, C833 and C811.

When the power plug is connected to the mains voltage, the stabilised voltage over D829 (24V ) will charge C833 via R829.When the voltage reaches 14.5V across C811, the control circuit of Q810 is turned on and the regulation starts. During regulation, Vcc of IC7110 will be supplied by the rectified voltage from winding 7-9 via L832, D832 and C833.

Control circuit

The control circuit exists of Q810, C802, C804, C807, C809, C810, R802, R803, R804, R807, R808, R809 and R810. C802 and R810 define the frequency of the oscillator.

Power switch circuit

This circuit comprises MOSFET Q825, Rsense R826, R827 and R828, R825, C827, L825, R812 and R813. R825 is a pull-down resistor to remove static charges from the gate of the MOSFET.

Regulation circuit

The regulation circuit comprises opto-coupler Q801which isolates the error signal from the control IC on the primary side and a reference component D881. The TL431(D881) can be represented by two components:

a very stable and accurate reference diode a high gain amplifier

K

R

2.5V

A

CL 96532076_036.eps

290799

Figure 8-17 ‘TL 431’

TL431 will conduct from cathode to anode when the reference is higher than the internal reference voltage of about 2.5V. If the reference voltage is lower, the cathode current is almost zero. The cathode current flows through the LED of the opto-coupler. The collector current of the opto-coupler flows through R806, producing an error voltage, connected to voltage feedback pin 14 of Q810.

Demagnetisation

The auxiliary winding (7-9) voltage is used to detect magnetic saturation of the transformer core and connected via R801 to pin 8 of Q810. During the demagnetisation phase, the output will be disabled.

Overvoltage protection circuit

This circuit consist of D814, C814, R814, R815 and R816. When the regulation circuit is interrupted due to an error in the control loop, the regulated output voltage will increase (overvoltage). This overvoltage is sensed at the auxiliary winding 7-9.

When an overvoltage longer than 2.0 (s is detected, the output is disabled until VCC is removed and then re-applied. The power supply will come in a hiccup mode as long as the error in the control loop is present.

Secondary rectifier/smoothing circuit

There are 5 rectifier/smoothing circuits on the secondary side. Each voltage depends on the number of windings of the transformer.

The -8V supply is regulated by voltage regulator Q871.

On/off circuit

24

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Contents Service Manual Brazil USAEurope / Trading AmericasPlayback & Recording and Disc CDR loader CDR main module CDL4009 or MAR770 This PCB contains the headphone socketTechnical Specifications GeneralESD IIIService Hints Service Tools Status of player Dealer modeDealer diagnostics Electrical service diagnostics Software versions, test for defective componentsMechanical service diagnostics DC-erase service mode Erasement of complete CD-RWFaultfinding trees CDR-ModuleCD-DA Disc Loaded CD R Display no Wiring Power Supply Voltages Electrical Service DiagnosticsCD-RW Disc Loaded CD RWCD Module Check Flex Connection from CDR Main Board Power Supply+3V3 AT IC7000 Pins 5,17,21,57, Check Safety Resistors OPEN/CLOSECD Module Playback General description Display BoardDescription of display board Display controller TMP87C874FTest instructions Clock signalControl signals Supply voltagesRotary operation IR receiver remote controlEasy jog knob Push button operationControl Signals Display board troubleshooting guideClock Signal FTD Drive LinesDescription of controller MC44603 Power Supply Unit P816Description of P816 Pin connectionsVCC Pin function descriptionPin Name Start up sequence of P816 Block diagram of MC44603Operating description of MC44603 Regulation of P816Ch1 Drain voltage Ch2 Drain current Ch3 Gate voltage Circuit description of P816 Troubleshooting P816 CD Main BoardMeasurements Block DiagramDescription Pin Configuration Test points on driver Input conditions conn 1006 pin Outputs connUcoil Vcoil Wcoil Hallu Hallv HallwDC Settings HF PathTransfer Characteristics Hfdet SettingIIS CLK11 Nmute DAC Amplifier Wiring Diagram Pink12V CD WY01at conn.F934of WY02 WY03 WY04 CDR main board10 D5V WC01at conn.1209 WC02at conn.1400 W801at conn.1500Block Diagram CDR Main BoardSchematic Diagram and Parts Location PY46Switching Power Supply PCB. P816 Q810 Q801 Q891 Q871 Q825 Q861 Q862 Q851 Q892QN54 QN53 QN58 QN57 Q311 Q681 QF52 QF51 QN52 QN51 QG56 QN55 QY01 QY02 QY04Exploded View and Parts List Packing Not Standard Spear PartsElectroly CAP Electrical Parts ListCeramic CAP P816-SEMICONDUCTORS P816-POWER Circuit Board P816-CAPACITORSP816-RESISTORS P816-MISCELLANEOUSPP16-SEMICONDUCTORS PP16-REAR Panel Circuit Board PP16-CAPACITORSPP16-RESISTOR PP16-MISCELLANEOUSPY36-ROTARY Encoder Circuit Board
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