Ct-100

[Tom Albrecht]

John,

Here are some pictures to show exactly what you're referring to. The first is a NOS FLY-107 flyback with no circuit connections. The second is the same flyback, but with the filament winding for the HV rectifier shorted directly. The third is with an actual 1B3 filament across the filament winding.

These all show the expected behavior. A dead shorted turn has a huge effect, and a turn shorted with a small, but finite resistance, has a noticeable, but smaller effect.

The CT-100 flyback cases I've shown always had both the HV rectifier (3A3) and the focus rectifier (1X2) unplugged, since I was aware that this could be an issue. In the case of the post above with 6 pictures, the CT-100 flyback was tested with no connections whatsoever (no yoke, no filaments, no pulse windings connected to anything).

The one case I want to go back and double check is the Emerson 637 picture above, where I mention the yoke is disconnected and other connections didn't matter. I definitely tested it with the 1B3 removed, and also tested with most other connections removed (including yoke), but I want to make doubly sure I did it with all of the above disconnected simultaneously.

The Crosley 9-407 case above had everything connected, including HV rectifier tube filament.

So far, all tests are consistent with the CT-100 flyback having a shorted turn. The only confusing cases that are causing me to hesitate are the ringdowns on the Emerson 637 set, where I did not see the expected result for a working flyback.

The CT-100 ringdown isn't as fast as the direct shorted case posted here, but I think that makes sense. Shorting the filament winding has very low resistance, since the filament winding is thick wire. An unwanted short inside the HV winding (such as what I think I have on the CT-100 flyback) will have higher resistance both due to much thinner wire, and possibly because the short itself has some resistance (dirty/burned contact point).

This has turned into quite a sidetrack, but I'm actually glad to develop a good technique for testing flybacks, with enough experience on many different flybacks to have decent confidence in the results. These ringdown scope traces are probably a more thorough method of testing than simply relying on what some particular piece of equipment says in a "good / bad" test.