Re: NST Shunt Removal (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Mon, 11 Jun 2007 18:04:05 -0400
From: otmaskin5@xxxxxxx
To: tesla@xxxxxxxxxx
Subject: Re: NST Shunt Removal (fwd)

This was brought up by another coiler in an earlier post, but I don't believe anyone answered it.  Does removing shunts make an NST more susceptible to failure, or is it a safe way to increase output?  Thanks for any advice, Dennis Hopkinton MA


-----Original Message-----
From: Tesla list <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Sent: Mon, 11 Jun 2007 9:24 am
Subject: RE: NST Shunt Removal (fwd)




--------- Forwarded message ----------
ate: Sun, 10 Jun 2007 18:33:34 -0700
rom: Jim Mora <jmora@xxxxxxxxxxx>
o: 'Tesla list' <tesla@xxxxxxxxxx>
ubject: RE: NST Shunt Removal (fwd)
Hello,
I too modified a France 12/30 removing half the shunts and potting it a
ixture of melted Vaseline and paraffin. It arcs a Really hot flame!
Jim Mora
-----Original Message-----
rom: Tesla list [mailto:tesla@xxxxxxxxxx] 
ent: Sunday, June 10, 2007 3:51 PM
o: tesla@xxxxxxxxxx
ubject: NST Shunt Removal (fwd)

--------- Forwarded message ----------
ate: Sun, 10 Jun 2007 16:05:07 -0700
rom: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
o: Tesla list <tesla@xxxxxxxxxx>
ubject: NST Shunt Removal
Hi All,
My 4.5" diameter coil spark lengths are far beyond a 12/60 NST capability.
ttp://www.classictesla.com/photos/ba45/ba45.html
nd these pics don't really show the lengths I've seen with this coil.
The NST I use was modified by fixing some hv windings and removing 1/2 
f the shunts (back when I documented the NST depotting procedure. So, 
he 12/60 Franceformer is no longer a 12/60. At the time, I never 
inished the measurements on the NST. Well, I rebuilt my hv divider 
oday using 6 100Meg HV resistors (mfg p/n EX2G1006, $1.66ea). These are 
ade by Ohmite and good for 7.5KV each (I have 3 in series on each leg 
or 22.5KV at 300Meg). Anyway, following calibration, I tested an 
nmodified 15/30 Franceformer. All came out as it should. Here's the 
ata for the unmodified 15/30 NST.
p=0.8 ohms, Rs=16230 ohms.
OPEN CIRCUIT MEASUREMENTS:
_pri = 124.1 V
_pri = 0.74 A
_pri = 24 W
A_pri = 91 VA
F = 0.27
_sec = 15340 V
SHORT CIRCUIT MEASUREMENTS:
_pri = 124.0 V
_pri = 3.83 A
_pri = 39 W
A_pri = 474 VA
F = 0.08
_sec = 25.74 mA

nowing that the hv divider is working well, I decided to unbolt the 
odified 12/60 and run it through both open and short circuit 
easurements. Here is what I found: btw, Rp=0.45 ohms, Rs=4660 ohms.
OPEN CIRCUIT MEASUREMENTS:
_pri = 124.2 V
_pri = 1.53 A
_pri = 50 W
A_pri = 190 VA
F = 0.26
_sec = 13380 V
SHORT CIRCUIT MEASUREMENTS:
_pri = 121.3 V
_pri = 20.3 A
_pri = 428 W
A_pri = 2457 VA
F = 0.18
_sec = 206.7 mA
So, as you can see, this NST is no longer a 12/60, closer to a 13/200 
nd that explains the arc lengths being so good, or really, "not that 
ood" considering I am about 20" shorter than I should be for this power.
Dr. Resonance was wondering why the little coil was doing so well and 
ad asked me offline. I let him know the NST was modified, but I didn't 
ave the data to give him at the time. I've probably pushed that NST to 
he brink of saturation, but, it has held up well, it just keeps on 
unning. It's reliability is a pleasant surprise considering what I know 
now" about the modifications.
I took out exactly 1/2 the shunts. I_sec jumped from 60mA to 200mA (more 
urrent than I intended). I was hoping removing 1/2 the shunts would be 
 linear jump to 120mA, but that was just a shot in the dark. If I were 
o modify an NST again by removing shunts, I would only remove 1/4 of 
he shunts. 1/2 seems a bit much. This NST is more like a PT or 
ombarder now. I really don't know how long it will last. Last week, I 
ost an XBOX 360 and my main computer (video section on motherboard 
ommitted suicide). This was due to a small 2" coil that I ran without 
n RF ground. Big mistake. However, my NST Terry Filter smoked with this 
.5" coil Thursday. The coil and NST still run great, but the Terry 
ilter has some burnt resistors. Looks like I'll have to check all those 
OV's!
Just thought this data might be of interest to anyone considering shunt 
odifications. I know those that happen to manage NST shunt removal like 
he fact they have (more power, baby!), but not everyone makes the 
easurements following the modification. And considering what I found, 
/2 the shunts removed might be stretching (or not depending on your 
iew of things).
Take care,
art





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