Picture wobble on this portable has got worse. There’s a
white hum bar on the screen but no hum on sound, and at
most times the field is unlockable.
Despite the absence of hum on sound, it would seem that
there is excessive 50Hz ripple on the supply. This is
probably due to failure of one of the rectifier diodes D601/2
connected to the mains transformer, or to loss of
capacitance in the associated reservoir capacitor C603