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Re: Need Secondary wire source
At 12:09 PM 07/31/2000 -0600, you wrote:
>Original poster: "Chris Brick" <cbrick-at-rebelbase-dot-com>
>The surplus magnet wire has let me down once again. Two secondaries lost
>to between turn dielectric breakdown. Does anyone have a good source for
>double formvar or better wire? I have found some quadruple coated wire
>(may be overkill) but can't find a supplier that will sell by the pound. I
>need about 5 pounds of 22 gauge asap.
I don't think your wire is the problem.
>Here are the specs on my coil:
>15/30 NST overdriven to saturation, then backed off a bit with variac
>4 boards of 18 .056 1600VDC Panasonic caps in parallel for .0124
>Adjustable spark gap with 7 gaps, air blown across to help purge ion cloud
>14 turns of .25" copper pipe spaced .25" at 15 degree bank, inner turn is 7
>It is tapped at about 8
>4x24 secondary on thin wall PVC drainpipe, dried and urethaned inside and
>out and after winding
>6x20 toroid mounted directly to the top of secondary
>To date I have had two secondaries start to burn between windings. My only
>guess is the enamel on the surplus wire is not thick enough. The burns
>have happened in various areas on the coil, usually near the center and
>start as a tiny black spot between two windings. The coil runs very well,
>giving me 36" streamers to air and sometimes streamers that almost hit the
>ground (about 44"). I have 2 more identical 15/30 NSTs and will be
>connecting them in parallel as soon as I get the secondary issue fixed.
Sounds to me like the coil is over coupled. Try raising your secondary up
a few inches. Better yet, build a flat spiral primary to reduce coupling.
>Thanks for any pointers,