if ur frequently losing the hot , check for cold solder joints on ALL flyback pins, driver xformer, deflection circuitry .
also check for excessive B+ voltage
there is usually a 'lytic bypass cap (1-10uF/160-250v) on the b+ side on the driver xformer.
when this cap degrades, the drive waveform becomes distorted .
this distortion affects the duty cycle of the horiz output xistor (hot). typical pulsewidth 12.6 us @ 15.750 khz
as the xistor stays on longer over time, eventually stress will cause the xistor to short.
qrz