Faultfinding Guide
GB 58 CDR7758.
8.2.2 Troubleshooting PSU 20PS317
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 CDR775. 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 :
1120, 3120, 2120, 3122, 1125, 3124, 5120, 6102, 2121
Check Vcc on pin 1 IC7110
Vcc = 12V...... 16V
Is power supply ticking?
⇒
Check start circuit and Vcc supply:
3123, 3134, 2129, 6129, 3129, 3111, 2111
⇒
Replace 7110
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 CDR 775
Check DC voltages
+5V, +12V, -8V, VFTD (-38V),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 6210/6211, 2210, 5210, 2213
⇒
+12V : check 6230/6232, 2230, 5230, 3230, 6231, 2233
±
1,41 x Vin AC
Turn input voltage up and check voltage across C2121,
this voltage should be
NOK
OK
Check fuse 1120 and
replace if necessary
OK
NO
⇒
Load on secondary output
⇒
Overvoltage protection : 5132, 6114, 2114, 3115, 3116
⇒
Oscillator voltage on pin 10 of IC7110 :
check 2102, 3110, replace 7110
⇒
Drive circuit : gate voltage of MOSFET 7125,
components 3112, 3113, 2113, 3125
⇒
Regulation circuit
- Measure voltage on pin 6 of IC7110 with oscilloscope
- If > 2.5V check the regulation circuit: 7200, 7201,
3201, 3202, 3204, 3205, 3206, 2201, 2202
3104, 3105, 3106, 3109, 2104, 2106, 2109
Check :
NOK
CL 96532076_037.eps
290799
To Next Page
Loading...
