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Many of the modern sets will shut down, to protect the CRT from burn-in, if the vertical deflection circuit fails. The first thing I'd check would be B+ voltage to the IC. If that's missing, you likely have a fusible resistor open and the resistor probably opened due to a shorted vertical output IC. Even if there's B+ voltage going to the IC, I'd still suspect the IC of being bad. Also, look for a capacitor, located close to the vertical output IC, that's rated between 47uf and 220uf @35-50 volts (100uf and 220uf are the most common values). When this cap starts failing, the viewer will notice thin white lines at the top of the screen. Over time, the cap will get worse and eventually blow out the vertical output IC. Unfortunately, most viewers continue to watch the TV until it loses vertical deflection. BTW, you'll also want to check any diodes in the vertical circuit, including the diode(s) that supply B+ voltage to the IC.
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