How to adjust screen size in model bplcv21bs2

The ST651 display adjust settings will vary depending on the specific model of your display, but generally, the settings that can be adjusted include:

1. Brightness: Adjusts the overall brightness of the screen.
2. Contrast: Adjusts the difference between the lightest and darkest areas of the screen.
3. Color temperature: Adjusts the color temperature of the screen, which affects the overall color balance.
4. Gamma: Adjusts the mid-tones of the screen, which can affect the overall contrast and color balance.
5. Sharpness: Adjusts the sharpness of the edges of objects on the screen.
6. Overscan: Adjusts the size of the image on the screen, allowing you to zoom in or out to fit the entire image on the screen.
7. Aspect ratio: Adjusts the proportion of the width and height of the image on the screen.
8. Color format: Adjusts the format of the color on the screen, such as RGB, YCbCr, and so on.
9. Audio settings: Adjust the volume, bass, treble and audio output settings of the display.

You may find these settings in the on-screen menu of the display and you can use the remote control or buttons on the display to access and adjust the settings. Some settings may not be available for certain models, and it's worth consulting your display's user manual for specific instructions on how to access and adjust the settings on your particular model.

If your's is the "s" model there is no keystone adjustment provided. Otherwise the keystone adjustment is found under MENU then 1, Size and Position and under MENU 2, Image Settings. Also, refer to this excerpt from the manual:
NOTE: This function is not available in "S" models.
Adjust the keystone control if images appears non-rectangular or keystoned in shape-that is, smaller at either the top or bottom edge. The effect of keystone adjustment is similar to
physically tilting the projector forward or backward in relation to the screen, and it affects all sources.
NOTES: 1) Keystone is enabled for a source only if Size is 1000 and Size x Vertical Stretch is 1,000,000.
2) Keystone adjustment is not available in "S"
models. 3) Avoid using Keystone with Blanking.

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To do this adjustment, you should enter the service mode option. If you wish to get some details; check the site linked here. Viewing it in "Mosaic" will make surf easy.
http://electronicshelponline.blogspot.com/
Service mode entry, adjust and exit procedure to many popular brand TVs are given.

Look for "Size" on remote, or go into menu under "picture", adjust size there.

There will be a "P.SIZE" key on the remote control. Please use it to choose the size of picture of your liking.

It would be helpful if knew the Make, Model of Laptop.

you can adjust the screen size from you remote control BY ZOOM, maybe some Model TV, had the design control MODE, you can adjust in 16:9
God bless you

What is the model number to your Sony TV?

Are you using a cable box like a DVR?...there should be a setting on that for aspect ratio, not sure this is a TV issue

There is no menu available for this adjustment. Without the specific model, I can't give you the exact cause. But, this is usually caused by one or more parts starting to fail in the vertical circuit. If I had this in the shop, I would look for bad capacitors in the vertical circuit before I started making adjustments.
Dan