stegu wrote:(If you didn't have 10 us/div on the scope, it may be the case that your rewinding of the primary resulted in a tighter winding (despite your thicker wire) which increased its inductance and brought the primary frequency down. In that case, your secondary may be right, or at least closer to the correct value, and your modified primary may be part of the detuning issue. The inductance of a coil is quite strongly dependent on its length, not only on the number of turns.)
Your arcing issues can probably be eliminated by applying more PU coating on the secondary.
Thx for the reply on the perf issue. I've been following the other thread.. However some of my posts weren't making it through... Needed moderator approval but Heidi might have since fixed that.
I am pretty sure (99%) the scope was on 20us. Yes the video was nearly useless, and seemed to have a lot of anomolies. I also counted the output (given the lousy video) and it seemed to have differing counts for the primary and secondary parts of the waveform.
The original primary had a real tight twist in the wire right before the windings, and even a kink I put in it with pliers when I was trying to get the wire tight, also there was a spot or two with a gap between windings. I also tested the old primary and two additional coats of polyurethane on the secondary; no change - still arcing. The arcing seemed to be originating from the "tight twists" I mentioned.
With the new primary (12awg was all I could find) I wound it as tight as I could, taped it to keep the windings together (clips would not fit anyhow), and kept the leads smooth, no excessive twists, no kinks. Btw, the oscilloscope video is with the new primary. I still want to get the tuning verified even tho it ~seems~ to be performing. We ran it for a fair amount of time at mostly high power... no blown IGBTs. Right now the testing blocker is "noise".. I need to pick a time so I won't irritate the neighbors (or figure out how to run the coil in the house.. It's kind of a small house B^).
Re the primary length: I definitely need to understand inductors a bit more.
It also cannot play some midi songs. E.g pirates-of-the-Caribbean, bumblebee.. Not sure why. Might be related to the midi player on the Mac (iirc it is midiwind), so I will give a windows player a try. Hopefully not a logic circuit issue.