I'm an amateur film-maker, currently planning a story which involves a scientist and his "time machine". I'm building this prop using various bits and pieces of electronic gear that I have accumulated.

I want to depart from the cliched look that most of these sorts of "machines" usually have, by making it a kind of hybrid of modern equipment and older electronics. I have a box of old radio/television vales that I picked up at a garage sale, and I will build them into the design.

There will be various LEDs sticking out at different places to simulate electrical activity, but what I really want is to have the valves, (which will be visible on the exterior of the machine), shown glowing, as if they are powered.

I wonder if anyone knows a way I can use batteries or perhaps a DC adaptor to energise the valves for this effect?

Thanks.

You can use batteries but the voltage you require will depend on the type of valves you have accumulated. Most of the radio valves from around 1939 onwards have 6.3 volt filaments though there are exceptions. A valve with 6.3 volt filaments will light up fairly well with a 6 volt 'dolphin' battery.

You would also need to consider how many valves you want to use. Four or five might get you two hours from the battery mentioned above but any more valves than that and you can cut that time back by a long shot.

If you let us know the numbers on the valves we can give you more precise information. One other thing to remember is to keep the valve power supply sperate to that powering the LEDs - a LED hooked up to 6.3 volts won't last long.

Thanks for that, Brad.

The valves are of various types and sizes. The biggest ones don't have any numbers but just "Super RADIOTRON" printed on th bases. They're 5-pin.

The other ones are smaller, about 2-3 inches, and have 9 pins. Some of the numbers on those are;

6CM5/EL36
Philips 6CM5
RCA 34/73? 6GW6 6DQ6B RC
Mullard 6CM5
Miniwatt 1B3GT

The rest are much smaller, have 9 pins, and have numbers like 6DS8 and Electron tube 4C printed on them. These also have a glass extended tip.

If it is possible to power these up using DC current, I can try different combinations of battery connections until one works. I can certainly have several batteries on hand.

Probably all I need to know is which pins to connect up, and which to avoid. I guess even a 12V battery could do some damage if it sent juice in the wrong way?

I would forget about the 1B3 and probably 34 as it is a 2V filament that is unlikely to put out any significant glow.

If you want significant glow you need something like an 01A (UX-201-A) with precautions ...5V.

The octagonal based 6CM5 and 6DQ6 are 6.3V and will draw slightly more than 1Amp.

Bases are available and the heaters are pins 2 & 7, these being the second pins from the spigot.

6GW8 is also 6.3V however its heater pins are four & five, looking at the base end. Still needs around 3/4 of an Amp

You can find the heaters with an ohm meter.

If you are only powering up the heaters with a 6V battery (if they have not failed) there is no major risk, as getting the pinouts wrong will only mean, no heaters.

With the 6.3V valves as long as the voltage is correct it maters little if you use AC or DC in your case.

There should be no strobing with AC as they are high thermal inertia heaters.

Marc

Digressing slightly, but sort of on theme, this thread reminded me of the granddaddy of "lab" effects which was auctioned off some years ago:

http://www.youtube.com/watch?v=edozYtAZx_w

IMHO, it has never been topped.

Marc,

Thanks for that info. I should mention I'm clueless when it comes to the technology of radio valves. I bought the valves from a garage sale, thinking that I migth have a use for them to use them in a film or stage prop, (which I make for an amateur theatre). And now I am.

I've got a bunch of AC and DC adaptors and I've tried several of the valves, by touching the wires from the adaptor to each pin in turn. In several cases, they glowed quite brightly. But only when a particular pair of pins was touched.

For one of them I used a 10v AC at 300milliamps, and it glowed quite brightly. I left it on for about an hour, just to see if it would keep working, but unfortunately it seems to have burnt out now. Good thing I've got plenty more.

In each case, I simply attached the pos and neg wire to only two of the 9 pins. Only a specific combination of two pins worked.

So, is it the heater that actually provides the glow in a valve?

You can see I'm a complete novice!

Thanks for your help, Marc.

Couldn't agree more, GTC. That's scene is the benchmark for "mad scientist's" laboratories in film.

Even though it could be recreated easily today with particle software, I think the atmosphere and intensity of the scene was unique. I haven't seen a movie scene since, that quite captured the same intensity.

And how many people have mimicked that manic line, "It's alive!", in that "insane" tone that Colin Clive used?

One of a kind.

Tank,

A valve is basically a switch. To explain things is simply as possible there are two electrodes (plate and cathode) inside a valve and a heating filament is placed close to one of them. There is a vacuum inside the valve envelope to stop the filament melting. Then one of the electrodes, known as the cathode, is heated by the filament an electric current is forced toward it, or as is said in some tutorials - electrons are forced away from it.

Further control, such as amplification of an audio signal, is permitted when grids are placed between the plate and the cathode. As mentioned by Marcc, pins 2 and 7 are usually the heater terminals on an octal valve. The other pins are for the plate, cathode and grids and on some valves there are pins that are not used. In your applications only the filament pins will be useful.

The heater filament is usually the only part of a valve that glows and is the only part of most valves that operates at extra low voltage (32 volts or less).

You mentioned that you have some plugpacks handy. Make sure these deliver enough current to run the valve filaments or you will overheat the plugpacks. I would actually recommend you run the valves from a 6 volt gelcell battery similar to those found in alarm panels with an amp/hour rating of at least 10Ah.

One thing a valve won't tolerate for long is being fed too many volts. A typical 6.3 volt filament will have a warm glow but if the orange turns to yellow then you'll run into problems eventually.

The filaments/heaters in valves are the things that glow red. The vast majority of valves you'll find these days give a clue to the filament voltage in the first digit of the valve's type as stamped on the glass.

For instance, a 12AU7 has a 12 volt heater, a 6X5 has a 6 volt heater, a 5Y3 has a 5 volt heater, etc.

As mentioned above, don't run the heaters at voltages higher than required, or they will burn out pretty quickly.

Brad's idea of a battery is good one because heaters draw comparatively high currents and as you add more to the circuit so the current draw grows cumulatively, and a battery is a better source of low voltage high current power than a plug pack. Here's an example of the battery Brad suggested:

http://www.batteriesplus.com.au/pd/815/273/century-ps6100/.

Of course, if you go the battery route, you'll eventually need the appropriate charger for it.

As you may have already noticed, the heater glow from some valves is more evident from the top of the tube, whereas other valves have a blackened top thus the glow is more readily apparent from the side view, so that may need to be taken into consideration for your filming.

Now that you have proved that over voltage kills the heaters.

I would suggest that you take serious note of the previous posts.

You will, as noted, need around 1.5 Amps per valve say 10VA. If you need a transformer the more amps the dearer they get.

You can put heaters in series i.e. use two valves and a 12V Battery. Consult someone with electrical knowledge if you are not sure.

With the 6CM5's to make a series 12V circuit: connect say, pin 2 of the first valve to Positive pin 7 to pin 2 of the next valve then pin 7 of the second valve to Negative.

For pinouts (which are taken looking at the base) refer to "Franks Electron Tube Pages"

http://www.tubedata.info/.

Marc

Guys, I'll answer all your posts in one go.

I now know what I needed to know, thank you all very much.

I think I'll just get a few dolphin 6V batteries and hook up only two valves to each of them. They won't need to run for any significant length of time, (just long enough for the shot, and that's usually less than ten seconds.)

As for the visibility, I will do a close up shot and them dolly out to a mid shot, so the glow of the valves will only need to be visible for the start of the shot.

Thanks again for your help. I'm now a smidgeon less ignorant than I was!