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A couple of thoughts: Quite frequently the HV (red) wire that wraps around the core of the flyback that supplies the filament voltage to the HV rectifier tube 3CU3, breaks down and arcs to the core of the flyback. There is usually 2 or 3 turns around the core of the flyback and they go down into the HV cup that the tube sits in and is connected to the filament pins for the 3CU3. If it breaks down it arcs, smokes, and grounds out the HV, usually ruining the HV rectifier tube. Simple fix, just get some good 30KV or better HV wire, take the socket out of the cup and replace the wire, paying close attention to the number of turns around the flyback core. Yes, there is at least 24KV between the wire and the flyback core. Also another thing that i have seen happen is that the HV cup itself develops a crack or a spot in which the HV will arc through to the chassis. In this case you just need to replace the HV cup. Of course clean all the gunk off of the wires, socket, etc. Sometimes this gooey residue will also cause arcing. Since you get a good healthy arc off the connector to the 3CU3 coming out of the flyback with the rectifier tube removed, I think your flyback transformer is ok. Although the 3CU3 could be weakened or bad and also possibly the horizontal output tube.
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09-14-2017, 08:51 PM
). It ain't what techs did back in the day, but with some cups NLA it is sometimes the best approach.
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