3 cd main board – Marantz MAR770 User Manual

Page 27

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25

8.2.2 Troubleshooting

P816

Figure 8-18

8.3 CD

Main

Board

The CD main board is built around the compact disc
mechanism VAM1250 and a loader 1250. The CDM delivers
diode signals and an unequalised high frequency signal. These
signals are necessary inputs for the decoder CD10. Based on
these signals the decoder will control the disc. The decoder is
able to control the sledge, focus motor, radial motor and turn
table. When everything is "locked", the decoder delivers a
digital output according to IEC958 standard, subcode to the
microprocessor and I2S for reproducing analog audio signals
by means of a D/A converter.

The microprocessor controls the CD10 and is slave of the
master processor on the CDR main board in the DR6050. Both
processors communicate via a DSA connection (data, strobe
and acknowledge).

YES

OK

Connect the mains inlet to a mains

isolated variac

Check the functionality of the following components :

F820, R819, C820, L820, D802, C821

Check Vcc on pin 1 Q810

Vcc = 12V...... 16V

Is power supply ticking?

Check start circuit and Vcc supply:
R823, R834, C829, D829, R829, R811, C811
Replace Q810

Power supply OK

Power supply unit OK

OK

NOK

NOK

OK

OK

Check the path of the other faulty voltage(s)

Power supply is OK
Check : - CDR main board

- Display assy
- CD main board for DR6050

Check DC voltages

+5V, +12V, -8V, VFTD (-35V),VDC1-VDC2 (3V8)

Check the +5V and +12V

Disconnect power supply unit from CDR main board

Connect dummy load resistors 10W,

15 ohm at +5V, +12V and ground

Check DC voltages

These voltages might be somewhat higher than specified

+5V, +12V, -8V, VFTD, VDC1-VDC2

OK

+5V : check D856, C857, L856, C859
+12V : check D866, C867, L867, R866, D868, C869

±1.41 x Vin AC

Turn input voltage up and check voltage across C821,
this voltage should be

NOK

OK

Check fuse F820 and

replace if necessary

OK

NO

Load on secondary output
Overvoltage protection : L832, D814, C814, R814, R815, R816
Oscillator voltage on pin 10 of Q810 :
check C802, R810 replace Q810
Drive circuit : gate voltage of MOSFET Q825
components R812, R813, C813, R825
Regulation circuit
- Measure voltage on pin 6 of Q810

with oscilloscope

- If > 2.5V check the regulation circuit : Q810, D881

R881- R885, C881, C882, R804 - R806, R809, C804, C809

Check :

NOK

CL 96532076_037.eps

290799

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