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1. remove the plate cap lead from the horizontal output tube. Connect an alligator clip lead to the lead and to a voltmeter (carefully). Don't put the cap back on the tube--turn on the set and check for DC voltage...if there is around 300-400 volts or so then the damper tube, flyback primary winding, and B+ power supply should be OK...if no voltage, troubleshoot in these areas till you get DC at the plate lead.
2. If this test passes, attach a neon bulb to a nonconductive stick and reconnect the plate lead to the HO tube. Carefully hold the neon bulb near the insulation of the HO plate lead (no direct connection) and the lead going from the flyback to the tripler. If it lights, there is HV AC being generated in the flyback, and there may be a problem in the tripler.
3. If bulb does not light...
Check grid voltage on horizontal output tube...should be -30 volts or more.
If not, there is either weak horizontal oscillator output or the tube is open.
I have had some sets with no HV and the problem was a bad HO tube that was destroyed because of no horizontal oscillator output. Check the voltages on the oscillator tube and if you have a scope, scope the grid input to the HO tube and make sure you have a signal. You may just need a new output tube, but do check the oscillator to make sure the new one doesn't burn up.
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