Failed NST

• To: tesla-at-pupman-dot-com
• Subject: Failed NST
• From: "Vivian Watts" <V.C.Watts-at-btinternet-dot-com> (by way of Terry Fritz <twf-at-verinet-dot-com>)
• Date: Fri, 23 Apr 1999 14:27:37 -0600
• Approved: twf-at-verinet-dot-com

Hi All,
    Today was a bad day.  After several weeks of constructing a Synchronous
Rotary Spark gap and trying it out on my coil it appears my NST has failed.
I have the ability to alter the phase of the rotary in real time and was
adjusting it while sparking when the sparks just stopped.  The rotary was
still arcing but no sparks from the toroid.  I can only assume my safety gap
was set to large an the NST has been damaged.

The failure mode of the NST appears to be it now gives half the voltage
expected.  That is 5000v instead of 10,000v.  This I have measured by
applying about 24V in and get 500v out.  So this would be 240v in to give
5000V.  The NST is centre tapped and each half gives half the expected
voltage.  Short circuit current is as specification 50ma at 240v in.
Resistance of each half is about the same at 2.7K.

Never having seen the construction of such a transformer I can only assume
some part of the high voltage winding has gone short but I am surprised it
appears to have happened on both sides.

Any thoughts on repairs before I hack into it!!!

Regards

Viv Watts UK.

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