CPD-420GS - Sony Monitor Service Manual (repair manual). Page 14

1) Using an external DC Power supply,  apply the voltage

shown below between cathode of D908 on  "D" Board
and GND, and confirm that the HV Hold-Down circuit
works. (Raster disappears)

Apply DC Voltage: 21.5 + 0.5 VDC

Check Condition
• Input voltage

: 120 + 2 VAC

• Input signal

: (fH = 94 kHz), White Cross Hatch

• Controls

: CONT (max) &  BRT (center)

• B+ Voltage

: 181 + 4.0 VDC

1) Using an external current source, apply 1.30

 + 0.05 mA between pin  11  of FBT
(T501) and GND, and confirm that the voltage
at CN801 pin   1   is 2.25 VDC or less.

Check Condition
• Input voltage

: 120 + 2 VAC

• Input signal

: (fH = 94 kHz), White Cross Hatch

• Controls

: CONT (max) &  BRT (center)

1) Input white cross hatch (fH = 94 kHz) signal.
2) CONT (max) &  BRT (center)
3) Input voltage: 120 + 2 VAC

:  Use NF power supply or make sure that

distortion factor is 3% or less.

4) Confirm that the voltage is within the voltage

range shown below.

Standard voltage: 181 + 4.0 VDC

              Part Replaced (

[)

                    

  RV904

              Part Replaced (

])

D - BOARD

     

 Allow the unit to warm up for one minute prior to

      checking the following conditions:

1) Input white cross hatch signal. (fH = 94 kHz)
2) Minimum CONT and BRT controls.
3) Cut off Screen VR (G2).
4) Input voltage: 120 + 2 VAC
5) Confirm that the voltage is within the voltage range

shown below.

                 Standard voltage: 27.0KV + 0.2KV

6) When replacing components identified by 

], make

sure to recheck the High Voltage.

7) Verify the High Voltage as  shown above (27.0KV + 0.2KV)

is within specification.    If not, set H. SIZE data at
minimum (-127) and then adjust RV904 on "D" Board.

8) After adjusting the High Voltage within specification,

put the RV cover on RV904 as shown below and apply
sufficient amount of RTV around RV904.

T901, R903, IC805, R921, R922, R812, D908, IC605,
R913, R914, D802, D909