Sony VPH-G90E, Service Manual

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5-9 VPH-G90E/G90U/G90M
5-5. VCO OFFSET/LIMITER ADJUSTMENT
Note: The electric power ( + +
+ +
+ 200 V) remains on the
PA board for several minutes after even
turning off the unit power. When withdrawing
the PA board from the unit, check that the
voltage of TP600 (
+ +
+ + +
200 HV) has dropped. In
case of hurry, it may be allowed to discharge
with the resistance of approximately 1 k
Z Z Z Z Z
/3 W.
In that case, withdraw the PA board after
checking the power voltage.
1. Turn off the power of the unit, then disconnect CN87
from the PA board.
2. Connect an oscilloscope to TP152 (HVDRV), and
connect a voltmeter to TP151 (VCO IN) on the PA
board.
3. Turn on the power of the unit.
4. Adjust RV101 (VCO LIMIT VOL) on the PA board so
that the voltage at TP151 is 2.00
±
0 .01 V.
5. Adjust RV150 (VCO RANGE) on the PA board so that
the pulse width at TP152 is 54.5
±
0.1 kHz
6. Adjust RV101 (VCO LIMIT VOL) on the PA board so
that the voltage at TP151 is 1.70
±
0 .01 V.
7. Turn off the power of the unit, then remove the
oscilloscope and voltmeter from the PA board.
8. Connect CN87 connected in step 1.
5-6. YA BOARD REPLACEMENT
5-6-1. Replacement Procedure
1. Remove the defective YA board
Remove IC233, IC333, and IC334 from the YA board
removed, and attach all to the new YA board.
* IC233 : Boot program/Uploader program
IC333 : User data save
IC334 : Factory data save/Service data save/User
data back up
2. During this time, be careful of the direction for
attaching the ICs, and make sure no pins are bent, etc.
3. Set the rotary switches of the new board to the same
value as the old board.
*
IC233 : Need not be replaced if the Ver. No. on
the ROM is the same.
4. Attach the new board to the unit and check operations.
If normal, the 7-segment LED on the YB board should
change as follows when AC is turned ON.
Red : 88 (Approx. 0.5 seconds)
→
Orange : 88
(Approx. 1.0 second)
→
Off
5. If images are displayed correctly when the power is
turned on, it means that the board was replaced
successfully.
→
Check the software version from the menu,
upload the program as necessary if the version is
old. Adjust the various data as necessary, and
create and save the factory data and service data.
(Refer to the next page for details on creating
data.)
If the board operations appear abnormal;
.
If an error code is displayed, follow the instructions.
.
If the 7-segment LED of the YB board does not change
from Red : 88.
→
The CPU-bus may be abnormal. Check the short-
circuit of each bus line.
.
Other problems after turning on the power.
→
Repair the circuit block with abnormal operations
(See Block Diagram).