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John:
This is intended for tube type TVs. The concept can be made work on solid state flybacks, but that's not the topic.
For this application, a cheap scope works out better than a good one.
Connect a small cap, about 33uuf to 47uuf at 500 volts or more to the plate of the scope's horizontal sweep oscillator plate, or buffer plate if it has one.
Connect the other end to an unused jack on the front of the scope or install a new jack for the purpose.
To test a flyback, run a wire from the new pulse output to the scope vertical input probe. Set the scope horizontal freq to the 30 khz range. You should see a drooping line from upper left to lower right.
WITH THE TV POWER OFF, remove 1B3 and damper and disconnect the yoke. Connect the scope ground to the chassis. Touch the probe to the horiz plate connection on the flyback.
On a good flyback, you will see a distinct ringing pattern with large sine waves on the left diminishing to the right. If it decays too quickly or does not ring at all, the flyback is bad.
Try it out on a good flyback to get the feel of the scope settings. Once you have marked the scope settings for a good transformer, a bad one will be obvious. If you have a known good flyback, you can simulate a bad one by shorting any two terminals together with a clip lead. You will instantly see the difference. Even shorting the agc winding will produce the result.
It will work on yokes as well, but the indications are not as consistent. It works on flybacks out of the circuit so you can test ones that are laying around the shop. Use the low end (B+ connection) of the primary for the scope ground and touch the probe to the HO tube plate connection.
That is essentially how the low cost flyback testers work. They just read the ringing voltage on a meter. I prefer a scope. Try it out and let me know if it works for you.
Don
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