The Sony CPD E200 (2000 model) monitor is known for capacitor failures,
high esr. Get out your esr meter and start checking. As an alternate
method when the unit just starts working ok after a cold turn on, take
some freeze mist spray and start cooling down the electrolytic
capacitors until the symptoms or squeeling and horizontal wavy lines
return.

The best method is to ESR check all the electrolytic capacitors,
especially in the smps, HV, and deflection stages. I usually find
about 1/2 dozen that are bad or nearly bad in that and similar Sony
models.