OT what is it?

It could be automotive timing light.

Ahh OK, That's a good guess.

Thanks, George H.

=0

As per Boris - yes, it could be a timing light - but definitely a stop-acti on device of some sort. I expect that there were other parts associated wit h it - strobe-type timing lights have an induction trigger device, usually, as one example. + & -attached to the battery, and the inductor clamped to #1 cylinder spark-plug wire.

Peter Wieck Melrose Park, PA

As per Boris - yes, it could be a timing light - but definitely a stop-action device of some sort. I expect that there were other parts associated with it - strobe-type timing lights have an induction trigger device, usually, as one example. + & -attached to the battery, and the inductor clamped to #1 cylinder spark-plug wire.

Peter Wieck Melrose Park, PA

But there is no trigger electrode. It might be Neon. Can you hit it with some high voltage, maybe from a lawn mower spark plug? See what the discharge spectrum looks like.

Hmm OK, I could try that.

I'm a little leery of mixing electronics with my lawn mower. Way back when, a motor wouldn't start, and I convinced myself it was a spark problem. I couldn't see a spark after all. I wanted to see how much voltage I was getting so I hooked up my DMM (though a series resistor), Pulled the cord to turn over the engine, and promptly blew up my DMM. :^(

George H.

Really, really, cheap timing lights, like from the J. C. Whitney of old, were just two pieces of spark plug wire with a coiled neon tube in the middle. The spark plug and the coil were the current limiter. They were very dim, and you could get chopped up by the fan trying to get them close enough to the timing marks to see anything.

Jon

That too. But a trigger electrode could also be down in the base somewhere.

Back when I drove carbureted VWs, I used a christmas tree light for a stati c timer. Seemed to work fine. I also had a neon timer such as you describe

- and it had that big fat lens as in the pictures. The inductive lights did not. Might be as simple as a neon strobe head...

Peter Wieck Melrose Park, PA

Tom, Sorry I chickened out and didn't put it across any of my working motors. (The last thing I want is to blow out the spark drive... I'm not really sure, what I'm saying. Is it ok to put a dead short across my briggs and stratton?

George H.

Doesn't the spark plug do just that when it fires?

What damages magneto ignition systems is open circuit, wire off plug events. Then the coil arcs internally.

Don't you have any kind of transformer that could make a HV spark with say a

Yeah, I didn't say my fear was rational. I had a bunch of old engines, I think most were "re-cycled" this past summer. Hmm, OK I'll hook it up to my old tractor. (Ferguson to-20) If I blow out the coil it's easy to put in a new one.

I've got a 120-24 (6A) tranny, how much voltage would you guess I'll need? I could run that backwards from a Variac.

George H.

Just take clip leads to the highest voltage winding (primary?) to the tube. Then use the battery to "flash" the lowest voltage winding. Think about how the points work in an ignition circuit.

No, do not use a variac.

All you want is to get a discharge through the tube and see what color is produced. Red says it might be Neon, blueish white may be Xenon, other will be who knows.

Thanks Tom, I got nothing with my big transformer. (I don't have enough current to get any significant voltage across the low voltage windings. It could also be that the tube is dead. I'll try with my tractor at home tonight.

George H.

Just be careful. Getting hit with the HV can really hurt.

Be a lot simpler to just to use one half of the tranny and use the back EMF from interrupting the circuit instead. Breaking the current through the longest winding should give enough of a spike to see if the lamp flashes.

Yes, but if it's a neon type you might as well bin it; they're so weak as to be virtually useless. I don't think this one is though, from what I can make out in the pictures.

When you touch the battery across the low voltage winding, it builds up lines of magnetic flux around the core - when you break the current, the lines of flux collapse onto the core and induce a high voltage spike in the big winding.

Most 9V batteries are very low energy density and won't keep up the current through a low voltage winding - and doing that wouldn't serve any useful purpose anyway.

Hook one wire of the low voltage winding to one battery terminal, then hook a loose length of wire to to the other end of the winding and just flick it on the other battery terminal.

You might get a small back emf spark as you break the primary current, but you should be able to rig a gap for a half-decent spark from the big winding.

If you're trying it with a 9V radio battery - they can't shift much current.

One of those 6V 996 lantern batteries with the springs on top would stand more chance.

The coil from a relay might be a better idea than a tranny. Some of those have a great many windings of fine gauge wire which would put less of a load on a 9v battery. I've got some here showing over 400 ohms resistance.

Back emf is good - but a step up ratio is *MUCH* better.