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I have found the best procedure for troubleshooting high voltage is:
1. Visual inspection, burned stuff, broken wires, unlit tubes, bad fuse, damper or HOT running rep plates, etc.
2. Make sure all tubes are OK
3. Check for RF on HOT plate cap using an insulated screwdriver and draw a purple arc.
4. Check for grid drive and screen voltage. If no RF, check for HOT plate voltage.
5. If there is RF, remove the 1B3 cap and look for a much bigger RF arc at the transformer cap. If no arc, replace cap. If significant arc, look for trouble under the 1B3 like shorted doorknob cap, filament winding or CRT air.
6. Check damper plate and cathode. Note damper cathode (boost) voltage
7.Disconnect yoke horizontal windings. Recheck boost voltage. If it increases much, the yoke is likely bad. If it stays the same or decreases, rule out the yoke for now.
8. If there is no smoke or overheating, let the TV run for a half hour. Turn it off and feel the flyback coil close to the core. If it is hot, the flyback is likely arcing internally. If not:
9. Recheck HO Tube control grid drive for proper level and frequency.
These steps should get you close. If not, it needs a couple of quick scope checks like frequency and ringing. It requires only a mediocre scope. HPs and Teks are overkill.
I prefer a VOM or VTVM for troubleshooting old tube stuff. They are less sensitive to low level RF riding on the B+ like boost and provide accurate DC resistance readings for inductors.
Don
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