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I spent some time last night and this morning trying to check the flyback and yoke in additional ways.
I have a Sencore SS137 Sweep Circuit Analyzer (picture attached) that I had not used before. I spent a little time making repairs to it (new electrolytics, fixed a broken wire) and confirmed that everything on it appears to be working properly. It has many functions, of which two are useful here. One is that it has a substitute horizontal yoke coil. Connecting this substitute yoke in place of the yoke in the set is supposed to tell you whether there is a problem with the set's yoke. Connecting the sub yoke, I find the HV is slightly higher (14-15 kV), but no where near where it should be, so my conclusion is that the yoke in the set is probably OK. It also measures the current in the substitute yoke and displays whether it thinks the flyback (and overall horizontal sweep system) is OK. Although the measurement doesn't seem very sophisticated, it does claim the flyback is bad (provided the surrounding circuitry is functioning normally). The meter has lines for various deflection angles of black and white sets (above line is good, below bad), and a single line for "color" sets, requiring the highest amount of measured signal. My result was that the meter came up to the level for a 50 degree B&W tube, which is way below what is deemed correct for a "color" tube. Not sure I trust this one-size-fits-all test, given that the 15GP22 is probably a bit unique, and its sweep system may not have enough in common with what this tester thinks is appropriate for "color" to give a trustworthy result.
Fant's post above reminded me that people sometimes do a ringdown on a scope to check a flyback. Although I have never done that before, it occurred to me that although I don't trust the meter on my Ringer, it does put out pulses. I captured the ringdown on a scope (see attached photo). What do you guys think about the waveform?
The manual for the Ringer says 10 cycles is the boundary between good and bad, but I don't know how small a cycle needs to be before it is no longer counted. Perhaps one of you knows.
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