A interesting puzzle...assuming that the squealing is not coming from the speaker but from the chassis...
A totally white screen takes a lot of beam current so your symptoms could be due to a failing HV shunt regulator tube or associated components. Most color sets use a hold down circuit designed to quickly reduce the horizontal sweep output - which can cause a current spike in the flyback transformer and the core can emit a strange hissing sound (sound level depends on core design). The current impulses can also result in the picture to wiggle. Many circuit designs feed back a few turns off the horizonatl ouput xfmr to set the bias on the phase detector diodes in the horizontal oscillator/AFC multivibrator. Leakage here can also upset set the DC balance in the rectified waveform from the sync sep that sets the grid bias on the multivibrator circuit. Again, the picture can wiggle. Finally, the B+ (usually 260 - 275 volts) that drives the hoizontal oscillator may have a lot of ripple during bright white picture scenes due to the increased beam current. A bad cap in the power supply could be the culprit too.
Role up your sleeves and dig in!
