Troubleshooting And Adjustment Procedures; Replacement Of The Main Pwb - NEC VT440 Service Manual

3. Troubleshooting and adjustment procedures

3-1. Replacement of the MAIN PWB

<Copying of the V-T data, ADJ data, Logo data, and Uniformity data>
Let the PJ power supply stay in the STAND BY state and select the [Data] tab for servicing software.
Make data read/write according to the descriptions (1) and (2) below.
(1) Data Read
Prior to the replacement, and as required, read the presently used data of the MAIN PWB and save
them in the relevant file.
(According to the type of fault, it may be impossible to save these data.)
Designate the file name and save the data by clicking the relevant [Read (PJ->File)] button of the V-T
data, ADJ data, Logo data, and Uniformity data.
(2) Data Write
After the replacement of the MAIN PWB, click the relevant [Write (File->PJ)] button of the V-T data,
ADJ data, Logo data, and Uniformity data to select the saved file, and write the data.
If it is impossible to save the data of the MAIN PWB used before the replacement, write the V-T data
of the model from the file as required, using the [Write (File->PJ)] button of the V-T data.
After all the data have been written, pull out the AC cord of the PJ and confirm that the Power LED is
unlit. Since then, connect the AC cord again.
<Adjustment of Sub-Brightness/Sub-Contrast>
Select the [Sub-B/C] tab for servicing software.
Make the respective adjustments of RGB/Component/Video according to the descriptions (1), (2) and (3)
below.
(1) Adjustment of RGB Sub-Brightness/Sub-Contrast
Select [RGB] in the Auto ADJ box.
Make adjustments by either method of (a) or (b) below.
(a) Auto adjustment
As an adjusting signal, enter an input of Window (Center: White) with the use of an RGB signal
generator. Otherwise, enter an RGB output of the personal computer. (When the PC output is
used in the auto-adjustment mode, the screen is automatically changed over to the Window screen.)
When the [Auto] button is clicked in the Auto ADJ box, automatic adjustment is started.
After the completion of automatic adjustment, confirm that there is no coloring of the gray scale.
If any coloring is perceived, make fine adjustments of (b) by manual adjustment.
Note: It is impossible to carry out normal adjustments if the definition (VESA XGA 70Hz) or the
pattern is improper for the adjusting signal.
(b) Manual adjustment
If the automatic adjustment is impossible, manual adjustments should be carried out.
As an adjusting signal, enter an input of gray scale with the use of an RGB signal generator.
Otherwise, enter an RGB output of the personal computer and display a gray scale with the use of
the [Scale] button in the Test Pattern box.
Use a scroll bar to adjust Sub-Brightness/Sub-Contrast, making sure not to cause black and white
chroma and also coloring in the gray scale.
After the completion of manual adjustment, click the [Set] button in the Data box.
METHOD OF ADJUSTMENTS
5-3