Tesla List wrote:
> > > > Subject: Re: repair
> Subscriber: major-at-vicksburg-dot-com Fri Jan 31 23:12:03 1997
> Date: Fri, 31 Jan 1997 23:38:56 -0600
> From: RODERICK MAXWELL <major-at-vicksburg-dot-com>
> To: Tesla List <tesla-at-poodle.pupman-dot-com>
> Subject: Re: repair
> I just unpotted the first of four neon transformers that I got from a
> sign shop in town. The guy there told me they were 15Kv -at-30ma. I'm sure
> they are 15Kv but not so sure about the current rating as the plates
> have all been removed. I kind of went back to the dark ages in the way I
> removed the potting. I boiled them in oil! I used a burner out of a old
> space heater to heat the metal pan pan filled with diesel! I know this
> sounds dangerous folks but it was a good 20' away from anything that
> would burn including yours truly. It really speeds up the process as it
> uses solvent and heat to disolve the tar. Just don't try this at home
> folks! The core looks, and disassembles the same way discribed in the
> archives. One secondary reads megohm resistance and is probably fried.
> The other reads a little over 8kohms. Is this the usual resistance of a
> 15kv secondary? Or is this side shorted???
> Frankensteins Helper
Wow - you must like to live dangerously! :^) Then, I guess coiling
itself is not completely without risk either...
Anyways... The resistance of a neon secondary should be measured with an
analog VOM. Digital meters tend to get "confused" when presented with
all the inductance in the secondary. The DC resistance of a secondary
winding will vary by manufacturer and model. Also, some manufacturers
have switched to aluminum wire to save weight and cost - these will run
higher DC resistance than for copper wire.
In general, 60 MA transformers will have significantly lower DC
resistance than the 30 MA ones, irrespective of output voltage. This may
imply that they can be "pushed" further (by running at 60 Hz resonance
with the tank cap, or by removing some shunt plates). Below are some
typical DC resistance measurements when going from a HV bushing to the
center-tap ground. Bushing-to-bushing values will be twice those below.
Also, your mileage may vary. :^)
Voltage MA DC Ohms (HV bushing to Center-Tap)
======= == =============
9000 30 11,000-13,000 (mini-size)
12000 30 9,000-11,000
15000 30 8,000-10,000
9000 60 2,400-2,500
12000 60 2,400-2,700
15000 60 2,000-3,000
Hope this helps, and safe de-potting to you!
-- Bert H. --