Quote:
Originally Posted by static1701
Tested the set this evening. Stereo works, solid state amp works. Television has issues: The sound works on the TV, once I was able to get the tuner to move I selected channel 10 (What my transmitter is set to) and I got a good clear audio signal. No raster because it has no high voltage at all. Tested all the tubes and replaced one 6GH8A and a 6JU8 that were bad. All other tubes are good. I am guessing the 3 can capacitors are bad. The heater was lit in the picture tube but that is as far as I can test it at this point, I don't have a CRT tester yet.
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CRT TVs from 1950 on use the horizontal sweep section to produce high voltage (second anode) for the tube. If the horizontal sweep is not functioning, there will be no high voltage. I would check the horizontal oscillator, output and damper tubes first; if any of these tubes are not lighting or are very weak, you will have no HV. A weak or dead HV rectifier tube will also kill the HV, as will any problems with the flyback transformer.
Do not, under any circumstances, try to measure the filament voltage on the HV rectifier tube. Although the tube has a 1-, 2- or 3-volt filament (1B3, 2AV2, 3A3, for example, the last two found mostly in color sets) and is powered by a single turn of very well insulated wire around the base of the flyback core, it is charged with the entire 2nd anode voltage from the flyback, which will destroy any standard digital voltmeter in the blink of an eye. The filament of the HV rectifier tube will not produce any visible glow if it is good. The only true test of this (or any) tube is to replace it with a known good tube, since most tube testers do not test vacuum tubes under actual operating conditions.
I would replace all three of those electrolytic can capacitors before doing anything else. If one or more of those caps are defective, you can lose HV and have other problems with the set. Your TV is old enough that the electrolytics and other capacitors, especially wax-paper ones, may be and more than likely are defective and should be replaced as soon as possible. This is a general rule when repairing any TV or radio more than 20 years old, and certainly one made in the '50s. Defective capacitors, especially those in the B+ power supply, can destroy the TV's power transformer if the line fuse doesn't blow first. Defective caps in other parts of the set will affect the TV's performance, so, again, to restore peak performance to a TV as old or older than yours, replacement of every capacitor is the first order of business. Power transformers in TVs made in the '70s or earlier, particularly the latter, can often be NLA (no longer available), so it will be to your advantage to replace, at a minimum, every cap in the power supply, leaving the others for another time.