Sony PVM 14M4E bias controls do not change anything

[Anonygoose]

I have two 14M4E with this same exact problem.

While calibrating both monitors, I found that bias controls do not change anything. Both monitors have had the deflection circuit recapped. Overall the tubes look very healthy and in the top ire range everything is fine and gain adjustments work.

In the low ire range, the picture is extremely red in color and needs a bias adjustment. Yet changing the values for any color does not change anything.

Any ideas on what could be causing this?

Thanks in advance