The 12, & 26 volts both feed the vertical IC. TDA 8172,
I think. Check for burnt resistors (some will be discolored,
but are fine), check caps, & the diode by the vert IC, replace
the diode, to be sure. Unload the vert IC, to see if the 12, & 26
volt lines come back up. Some T.V.'s won't come on with bad
vertical circuitry. I know you replaced it, but the flyback causes
the "three strikes your'e out" problem, in larger RCA sets. If it's
not the vertical, I think it is though, maybe you have a bad high
voltage capacitor, or bad horizontal drive waveform. Sky.