NotTaR of Television Sets : Excessive B+ from fixed regulator like S..  
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Excessive B+ from fixed regulator like STR30123/STR30130/STR30135

These are fixed regulators that do fail but the problem may be elsewhere.

If the B+ goes to high, the X-ray protection circuitry may kick in and shut down the horizontal deflection.

If there is little or no load (horizontal deflection not running at all), all bets are off as well - the resistor that is likely across input-output will dominate and boost the voltage above the proper output for the regulator chip. Use a Variac to bring up the voltage to the TV. If the deflection does not start up at any voltage even with the B+ ramping up past its normal value, the problem is probably in the horizontal deflection/startup circuitry, not the regulator.

Some of these may go out of regulation if the output electrolytics are dried up. There might a a 10 uF 200 V or so electrolytic across the output to ground. Test it or substitute a known good one of about the same uF rating and at least equal voltage rating. If you can get the TV to work at reduced voltage using a Variac (but possibly with hum bars in the picture and hum in the audio), check the output capacitor.

Otherwise, it could be the regulator or one of its biasing components (sets current to B input - the voltage at this input should be close to the output voltage value). Also check to be sure the input voltage is solid - main filter capacitor is not dried up.