Another RCA service bulletin on the CTC 5

[DavGoodlin]

In a similar way starting with CTC12 chassis, RCA tied the CRT cathode bias to the shunt regulator grid.
This allowed shunt regulator to be cut-off during extremely bright scenes, regulate only during darker material to maintain load on HV supply.
It seemed to reduce a "blooming" issue with a CTC11, was tough to mitigate with just HV, brightness/contrast controls.