What you describe does not sound like a bias issue. If it was a bias issue then you would have the whole screen tinted a color and not just a corner.
What you have sounds like a purity issue. To adjust the purity turn the set on and use a seperate degaussing coil to degauss the screen of the set, and if it looks good then stop there.
If degaussing fails to fix the issue then either connect a signal that gives a blank red screen or set up the set for a blank white raster and turn down the blue and green screens until you have a red raster. Then slide the deflection yoke as far back as you can without disturbing the other neck hardware so that your screen resembles the picture below. Then use the purity rings to center the red spot on the screen. Once done slide the yoke forward untill the whole screen is an even red. Turn red down and then turn up the blue and later green individually and see if the color is consistent over the entire screen if not slide the yoke back again and repeat from there. If all three primaries are consistent when viewed separately then readjust the screen controls according to the sam's manual procedure.
