The Geek's Guide to NST's - was- Strange neons

["Christopher Boden" <chrisboden-at-hotmail-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

>Original poster: "Dan Kunkel" <dankunkel-at-hotmail-dot-com>
>
>
> >
> >You're fine Dan! Just treat it like you would a egular NST. Is it White?
> >With a little handle on one side, a flip up lid with a screw on one end?
> >And
> >there's a little junction-box area in one end? That's like one of the 
>ones
> >I
> >have by France. btw, they're a DREAM to depot. :) And with a France, 
>that's
> >a plus. They have the life expectancy of about 30 sec.
> >
> >
> >Each of the WV wires is one end of the dual secondaries, and the Ground
> >(case) is center tapped.
> >
> >Christopher A. Boden Geek#1
> >President / C.E.O. / Alpha Geek
> >The Geek Group
> >www.thegeekgroup-dot-org
> >Because the Geek shall inherit the Earth!
> >
>
>
>
>you have described them to a T. is the best way to depot these badboys with
>the freeze and chip method?

Personally I abhorr (sp? who cares) the freeze and chip method. I have 
killed a LOT of NST's (and FITs, and computers, and Lasers...etc ad nauseum) 
so I spend a lot of time depotting them. Here's what I have learned....


The Golden Rules of Depoting.

1. Never freeze and chip. Every time I tried this (both of them) resulted in 
damage to the NST. Work them hot, not cold.

2. Never bake them indoors! Unless you LIKE the stench. If you do, get used 
to it. It lingers like a fart in church. If you bake one in an oven don't 
expect to make anything edible in there for a long while.

3. Start before noon, it takes a while. I average about 4 hours min.

4. Keep it hot. Once you start, you have to keep an eye on it for safety. 
It's a LOT easier to do the major cleaning hot.

5. Wear old clothes. Tar sticks to everything. It's like vaseline with an 
attitude. And it does NOT wash out easily.

Here's the method I use.

I place an old electric griddle in sandy/gravel area (it's a lot easier to 
clean up tar from sand than concrete). Near the house, on a side with CLOSED 
windows.

Place the Griddle on something solid (cinderblocks) and make sure the entire 
griddle is supported. Don't try to balance it on 1 block.

Go to Meijers (or whatever) and get a few of the stamped Al-foil baking tins 
used for turkeys and roasts. You will use them in pairs, get 4 or more, 
they're cheap.

Place one of them on the griddle, place 1 - 3 NST's inside, place another 
roasting tin inverted on top to seal in the heat.

Bake at 400F untill it starts to stink real bad. Check it every half hour to 
start, then (after about 3 hours) every 15 min.

You will need a stick (1/2 dowel works great) and a coffee can.

IMPORTANT NOTE:
When the tar is melted there is nothing to hold the core in place! If you 
invert the NST EVERYTHING will fall out and you WILL rip hair thin wires 
off. This is bad.

By now the tar will either be VERY soft or goopy (technical term for a 
gelatinous state). Use the dowel to GENTLY schlop off bits of tar. If you 
feel it snag on ANYTHING then don't FORCE it! There are little wires in 
there that break VERY easily. Take your time.

The Insulators on the end should turn by now. Turn them about 1/4 turn and 
pull GENTLY. Pull them JUST clear of the case and cut the wire CLOSE to the 
bolt on the insulator. Set them aside.

Lay the NST on it's side and let the tar run out into the coffee can. Save 
this, you may want it. (goes well with feathers)

When you have the vast majority of the tar out, cut the wires for the 
primary and center tap (primary will be the 2 big ones, tap will be 2 little 
ones to the case) then remove the CORE.

The CORE will be a big iron thingy with 3 spools of wire on it. About the 
weight of a brick. It is the actual NST. The Middle spool is the primary 
(heavy wire, low voltage). The end spools are each secondaries (high 
voltage, hair thin wire). Each secondary is HALF of your rated voltage 
7500VAC for a 15/30 NST.

Set the CASE back on the griddle and cook untill you can pour out all the 
tar. IF you want to put it back in there. I prefer a new case, homemade from 
Lexan and oil tight.

Scrape all the tar you can off the NST. It's easiest to do it now while it's 
too hot to touch. Be careful!

Let everything cool untill it's room temp.

I clean my NST's manually. Some soak in Gas or Kerosene, but that's tha lazy 
way and takes forever.

Clean everyting as good as you can. If you take your time (a weekend) you 
can get it almost pristine. But you REALLY have to want it.

If you're lucky, there will be a couple sets of metal shims that can be 
removed from the core. These are current limiting shunts. DO NOT REMOVE THEM 
ALL!!!! This is where potting in Oil is a wonderful thing. When you 
reassemble the NST you can remove it from the oil, remove A SINGLE PIECE OF 
METAL FROM EACH SET, NO MORE and test everything to see how it works. If it 
gets HOT than you went too far. Romove only one set of shunts at a time. 
They have to be removed in sets though, not just a single sheet from one 
bundle, but one sheet from each bundle. Everyting must be balanced.

Not all NST's have EASILY removeable shunts, some require a grinder, torch, 
or grenade.

Examine the NST throughly. Test it naked with low voltage from a variac. If 
it works after depotting alone then you had a Carbon Track in the tar. it's 
fine now. IF not then you have either an OPEN (broken winding from over 
current) or SHORT (2 ajacent windings touching or carbon tracked, or even 
welded from over voltage). There are only 3 basic failure modes for NST's.

You can repot in everyting from Mineral oil to Vaseline (it melts like 
butter) to the original Tar (if your masochistic).


HOWEVER:

The BOX type NST you have is MUCH easier. Just Bake it and there are NO 
insulators or wire connections to deal with, only the midpoint case Ground. 
MUCH easier to depot.


btw, if you use a SAFETY GAP, an NST FILTER (like Terry's) and Follow the 
rules of NST life support, you won't kill them. I haven't killed one in 
Months!

Rules of NST Life Support

1. Use a PROPERLY SET Safety Gap and DON'T MONKEY WITH IT!

Set the Gap to where it JUST BARELY does NOT fire with the NST connected to 
it. Then LOCK IT THERE AND NEVER MESS WITH IT! If you're properly set and it 
starts to fire then you're DOING SOMETHING WRONG and it's doing it's job in 
Telling you this. If you simply open it more and more you have defeated the 
purpose of having one in the forst place.

2. NEVER use a NON-Synced Rotary Gap with a NST. They allow the voltage to 
get too high and WILL kill it in minutes.

3. KEEP YOUR WIRES SHORT! Keeping your leads as short as possible (1' or 
less) for some reason beyond my understanding DRAMATICALLY increases the 
life of an NST. I don't know why, I know it works. Ask the Glass Benders for 
the details if your interested.

Some brands of NST's are MUCH more fragile than others. France is the worst 
(but the easiest to modify and depot), I swear by my Jensons, I love them, 
but they have NON removeable Shunts and are a pain to modify.



Alright guys, what did I forget?

Christopher A. Boden Geek#1
President / C.E.O. / Alpha Geek
The Geek Group
www.thegeekgroup-dot-org
Because the Geek shall inherit the Earth!

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