Good day all.

Bought almost 20 years ago at a gadget store and recently failed, perhaps lack of use. Had it attached to my stereo rack as behaves like a huge VU meter, varying the length of light with sound loudness. Never seen another, ever. No brand, no markings, no nothing to identify. Would like to learn about it before handling it wrong in attempt to repair.



The gas / plasma/ whatever inside its clear tube glows red and has only one terminal apparently fed by some high voltage I prefer not to bite me supplied from the bottom base circuitry which includes a microphone and sensitivity potentiometer. Powers from a 12VDC plain wall wart. The red glow on the far right surface is just a reflection. Has nothing to do with LEDs It is gas glow.

What is it ? How does it work ? Any similar gadgets that you know of ?





Would these compare ? ----> https://www.alibaba.com/product-det...107.html?spm=a2700.details.0.0.1641404fS2cEX6

 

It looks like a neon glow tube, based on the color. I have used NE-2 bulbs as RF indicators, and they will also glow if I hold the tube between fingers and touch the leads to the 60 Hz mains.
So what you have is a high voltage RF power oscillator with the amplitude varied by the audio signal somehow.
So the very first thing to check is the power source and connection. That tube is probably not replaceable for any money, so treat it gently. If the supply is OK, then with the power off and disconnected, you can open it and check the oscillator parts. A failed resistor or transistor is my guess.
AND be very careful with that transformer/step up coil, the secondary will be incredibly thin wire.

 

It looks like Neon as was mentioned. You may want to try a Google of "nixie in-13 vu meter". What you have and the mentioned tube may be cousins. This is an interesting read on the aforementioned tube. The tubes I see are a three terminal device and you may want to measure looking for any high voltage like 150 VDC or typical Nixie Tube voltages.

Ron

 

possible sound effects renovation:

 

Never related this gadget to a 'lightsaber', but if was battery powered, would be nearly identical to the one on the movie. Been resoldering pads and testing transistor junctions, sketching its schematic but does not work yet. Once I measured 130KHz just by proximity to a probe, at 25Vpp 10 cm away from the glowing tube. Confirming there is only one wire connected to the base of the glow tube. The 'neon' glow tube is glass inside a sturdy plexiglass tube for protection.

Will search as 'lightsaber' for results...




DC in, 78L12, microphone, potentiometer, selector switch, LDR, 5 transistors, transformer...

 

I am sure that this device predates Star Wars by quite a few years. In the photograph, is that white on the PCB glare, or a white substance? It may be that one of those 2 components near the black wire fron the power connector has failed. AND, where did that wire from the glow tube connect to?It has to be connected for the tube to light up.
That white stuff may be a good clue as to what failed.

 

Star Wars was first released in 1977. That board looks about right for that era.
Interesting, I see a LDR next to the transformer, did it also respond to ambient light ? Slide switch shows 3 positions.

 

Certainly the slide switch is a suspect, they do develop poor contact problems. And still, where did that wire from the tube connect? That is an important connection. And really, that deposit of white stuff tells me that some component has failed and vented, unless it is control cleaner from cleaning that variable resistor (the control pot).

 

Thanks.
Cannot discern the 'white stuff' . There is an aluminium strip as heat sink for a 2SD882 on its right driving the transformer primary.
Leftmost on board is an electret and 470uF/16V electrolytic with flash glare around them. No goo anywhere. The secondary ends of the rightmost transformer connect to common negative and to the single wire for the neon glow tube.
Yes, the LDR is for one of the selector positions, other position is sound reaction.

 

Getting closer... found this :

 

While the circuit makes sense I don't quite get how it works less a ground and only that single wire? Unless the glow length is based on the RF energy much like placing a neon tube in the vicinity of a strong enough RF field.

Ron

 

The high voltage at a high frequency allows the neon gas in the tube ionize and act like an antenna, so that is where the power goes! quite simple but not obvious. And if the switch connecting the emitter of the #441 to common does not get it oscillating then the problem is i the oscillator circuit, The transformer, two resistors, and the transistor.

 

The high voltage at a high frequency allows the neon gas in the tube ionize and act like an antenna, so that is where the power goes! quite simple but not obvious. And if the switch connecting the emitter of the #441 to common does not get it oscillating then the problem is i the oscillator circuit, The transformer, two resistors, and the transistor.

So with that in mind does the strength of the RF determine how high up the tube the gas ionizes? What I suggested above? The drawing leads me to believe that. I just never saw one.

Ron

 

Exactly! The stronger (higher) the voltage the more the gas can be ionized because there is more current flowing. A graphic example of an antenna working, sort of. The transistor in the emitter lead serves as a series amplitude modulator. It really is cool!
That other transistor, designated "431", may be adjusting the base bias of the oscillator transistor. So the operation of the circuit is actually a bit complicated.

 

Pretty cool and something I never saw done. Like many as a kid into amateure radio I had to put a few small neon tubes on the end of my antenna. Was interesting to neighbors when running CW.

Ron

 

Pretty cool and something I never saw done. Like many as a kid into amateure radio I had to put a few small neon tubes on the end of my antenna. Was interesting to neighbors when running CW.

Ron

Seems to me if I remember correctly, there was a brand of CB antenna back in the day that had a neon stinger of its tip.

 

Seems to me if I remember correctly, there was a brand of CB antenna back in the day that had a neon stinger of its tip.

There was, I think it was mentioned earlier in the thread. I recall it may have been a Firestik antenna brand name.

Ron