Florian Voelzke wrote:

> "Alexandre Domingos F. Souza" wrote:
> >         THIS is interesting. What about the lifetime of bulb? I'd love to see this thing working, hehehehehe
>
> Quite a while ago, I bought a similar one here in germany. I used it to
> build - an eprom eraser! And I too was much to interested to leave it
> unopened :-).
> These units use the fact that the small 4W tubes don't have the same
> high ignition voltage than the big, long tubes. The big tubes use
> (better: used) an inductor in series to limit the current and to produce
> the ignition voltage together with a small neon tube - the starter.
> In the unit I bought the inductance is replaced by a cap which provides
> the same current limiting. To ignite the tube there is a simple sort of
> peak voltage doubler which gives 650V (at 230V mains), which is enough
> for this small tube (in most cases...).
> The main disadvantage: The doubled voltage to ignite the tube is not
> enough in every case. It happened to me that I switched the unit on and
> nothing happened - until I touched the tube. I don't expect the tube to
> ignite at low temperatures, either.
> And because eagle is already running, I have drawn the following short
> schematic, ripped from my unit when I examined it. So sad that I don't
> have use for more 4W tubes, so I haven't yet cloned this device ;-)


Hi Florian, yes that circuit looks very similar to
the light I bought. Mine doesn't have the two 68ohm
series resitors to the tube, but instead has the wires
8 inches long. Probably a cheaper way of keeping the
RF down.

The capacitor and resistor values are slightly different,
but the circuit is essentially the same operation.

Just a note, there is a very important component, a
copper foil stripe that runs the length of the tube
and is attached to one tube wire. This is vital to start
the tube and is the reason yours doesn't start until
your finger touches the tube. Mine starts fine, and
quickly, even when quite cold. These foil stripes are
often used in cheap inverter fluoros.
:o)
-Roman

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