Marantz CDR631 Service Manual page 30

7.4.2 Troubleshooting P816
+5V, +12V, -8V, VFTD (-34V),VDC1-VDC2 (4V1)
Disconnect power supply unit from CDR main board
These voltages might be somewhat higher than specified
Turn input voltage up and check voltage across C821,
this voltage should be
Check fuse F820 and
replace if necessary
OK
Check DC voltages
OK
Connect dummy load resistors 10W,
15 ohm at +5V, +12V and ground
Check DC voltages
+5V, +12V, -8V, VFTD, VDC1-VDC2
OK
Check the +5V and +12V
OK
Connect the mains inlet to a mains
isolated variac
±1.41 x Vin AC
OK
Is power supply ticking?
NO
Check Vcc on pin 1 Q810
Vcc = 12V...... 16V
OK
Power supply OK
OK
Power supply unit OK
Power supply is OK
OK
Check : - CDR main board
- Display assy
Check the path of the other faulty voltage(s)
+5V : check D856, C857, L856, C859
OK
+12V : check D866, C867, L867, R866, D868, C869
OK
Check the functionality of the following components :
F820, R819, C820, L820, D802, C821
Check :
Load on secondary output
YES
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
OK
Check start circuit and Vcc supply:
R823, R834, C829, D829, R829, R811, C811
Replace Q810
Figure 7-26
28
CL 96532076_037.eps
290799