Emerson 612 Grid bias problem

[soliman15]

Hello, I'm working on Emerson 612 TV and found that audio is weak and the image contrast is not that good, after troubleshooting I found that the grid bias in final stages of both audio and video is lower than what the Sam's shows, in spite of having the correct B- voltage. The attached images have the Sam's voltages in black and the measured ones in red.
is this the reason for my TV poor performance and how can I fix it. thank you