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Re: NST question 30ma or 60ma not sure?
Hi Scott, Neal,
> Original Poster: Bunnykiller <bigfoo39-at-idt-dot-net>
> Hi Neal you can do the reverse amp check ...
> short the hi V> outputs and read the amps the 120V
> source draws and work the amps backwards from
> 15KV if you get a really oddball reading ( not 30 or
> 60mA ) then try the numbers with the secondary side
>at 12KV and repeat the numbers see how that turns
>out ...
I donīt think this will work correctly. You MIGHT be able
to tell if it is a xx kV 30mA or 60mA NST, but you wonīt
be able to tell if it is a 15kV/30mA or a 12kV/30mA (same
goes for the 60mA version). A transformer is ONLY lossless
in the theoretical world. In practice you will have all sorts of
losses. You also donīt know how *exact* these xformers
are. The sign doesnīt care if it is being supplied with 15kV
or 14.5kV (for example). The voltage breaks down anyway,
once the sign gas has been ionized and starts conducting. The
same goes for the current output. It could be anywhere from
25-35mA for a 30mA jobber. This holds even more true, if the
NSTs are from different manufacturers or different lots (DOP).
The easiest way is to take a meter and really measure the output
current. DO NOT touch the meter or the leads. You can use a
DVM, BUT switch it to the highest (10-20A) range. This is the ONLY
way to measure the current as the meter will act as a true short
ONLY in these ranges. The 10A or 20A range uses a 0.1 or 0.01
ohm measuring resistor. The lower ranges (200mA) WILL NOT (!!!)
save your meter. Usually the 10A or 20A are not fused (it says so on
the housing, near the 10A or 20A jack). DO NOT use any meter with
a fuse inside. If the fuses blows, you will have HV all over the SMD
electronics inside your DMM and you might as well chuck those bucks
right out the window (it IS the safer and less spectacular way to get
*rid* of any excess money you might have ;o} ).
Coiler greets from Germany,
Reinhard