Primary modifications

After some initial running, the plastic insulated primary I made started to flash over badly. I realised that the design actually makes the E-field worse. The thick plastic has a high dielectric constant, so the field in the remaining airgap gets concentrated more than it would with no plastic at all. I dismantled it and found it was quite seriously burnt.

The plastic was badly treed.

and ouch.

I reckoned the best course of action was to cut away as much of the plastic as possible so that's what I did. Later, I found that I had to remove a few turns from the top of the primary and raise the secondary up by 1", but that isn't shown in the picture below.

Primary with all extra plastic removed.

I don't have any objection to thin plastic formers such as PVC pipes. But the very thick HDPE that I used ended up being more of a hindrance than a help.

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