USAAF X-Ray Warning Light

[YoungManGW]

I have acquired a freestanding industrial X-ray warning light of the late 1960s, a large 'cone' with Lucite panels. These are illuminated from within. A flashing (rotating) red lamp on the top further attracts attention.

The light operates on 115v 60cy. Inside is a transformer, although the voltage this steps down to is unknown (X). Power is provided, I think, by way of either a three pin Hubbell connector (male) or a two pin US socket (female) - there are both, presumably to allow a chain of such lights to be set out around a working area.

I obviously want to get this working. To be able to determine the transformer's output I'd first need to acquire a 240v to 115v transformer and connect this to the light by way of the connector or socket.

What strikes me is that it's a bit silly to end up with two transformers. If I could determine the output (X) of that inside the light, I could instead rewire in one step with a 240v to Xv transformer.

Does anyone near to me, please, have any means of hooking the light up to a 115v input so that we can determine what X is, such that I can acquire the right new transformer and make a more elegant job of things? I don't have such means myself.

It's an interesting piece, and deserves to be lit. I am in Oswestry, Shropshire. Costs and tea requirements met of course. Very many thanks.

Regards,
Richard

[Station X]

Could you use a Variac?

[YoungManGW]

Yes, that's what I'm thinking, but I don't have access to one myself.

Regards,
Richard

[M0FYA Andy]

Have you tried removing the bulb to check for voltage markings? Sorry if this is a silly question.
Andy

[cheerfulcharlie]

You might be able to obtain a 115v out transformer from a site involved in selling/hiring secondhand power tools....some industrial/building areas use 115v drills etc.

They and the C form cable connectors are usually coloured yellow.

Another place to look is somewhere involved in scrap film projectors as some Bell & Howell projectors were direct imports from the US and thus needed a step down transformer

[turretslug]

A bit of a bodge- but surely a forum like this is the home of the work-around!- do you have an appliance with a 230/115V primary (dual or tapped) transformer of around 100VA or so, e.g. a hi-fi amp, biggish thermionic apparatus etc? That could be requisitioned in-situ with flying leads in auto-transformer mode with connection between 0V and 115V tappings to provide 115V power for secondary-side measurement.

100VA is just a number off the top of my head to allow a safe margin for loading and regulation, but a lower VA should be OK for judging from a quick measurement.

[russell_w_b]

Are you in a position to remove the lamp and connect it to a battery or LV power supply (train set transformer) or what-have-you? If you start low and look for a glow, you'll get some idea of the voltage by the brilliancy of the lamp.

Even if the lamp doesn't glow, or glows dimly, it'll give you some sort of idea of where you need to go next.

[Terry_VK5TM]

Disconnect the secondary of the transformer and feed a low voltage into it.

Measure the voltage on the secondary and then measure the voltage on the primary.

Calculate the turns ratio, from which you should be able to work out what the secondary voltage would be with 115v applied to the primary.

[russell_w_b]

The other thing you'll need to determine is whether the reflector rotator motor is the same voltage as the lamp. You may still need 115V.

[YoungManGW]

Thank-you for these helpful thoughts. Unfortunately, there are no bulbs to remove to check them for the voltage, and I don't have the means to feed in an increasing voltage. The notion of hunting down a power tools transformer is a good one, although I don't have a means of testing the internal transformer's output voltage once connected. Good point about the rotator possibly being 115v and the lamps being something else. Anyone nearby with a Variac and test gear?

Regards,
Richard

[broadgage]

The presence of a transformer MAY mean that frequency is important as well as voltage.
Use of a transformer on a lower frequency than intended will increase the magnetising current, unless the voltage is also reduced in proportion.

Many transformers are designed for operation on 50 cycles or 60 cycles, but it may be unwise to count on this.
A minority of American transformers were designed to operate over a range of 25 cycles to 60 cycles since there some 25 cycles supplies.

Use of a building site transformer may be OK since these have a nominal 110 volt output not the 120 volts for which American equipment is probably designed. The reduced voltage will PARTIALY compensate for the lower frequency.
I would try it, but keep a close eye on the transformer temperature.

The bulb is probably a standard vehicle type of 6 or 12 volts. These are preferred over line voltage lamps due to greater resistance to vibration and a more compact filament.

[TonyDuell]

Can you trace out the wiring to see just what runs off the secondary side of the transformer, and what runs directly off the power input? The motor for the rotating lamp might be 115V, it might be lower voltage running off the transformer.

Other than that, I go along with the suggestion of a power tool transformer, at least to test it and measure voltages.

[YoungManGW]

Yes, going to do that later today Tony. Will report back.

Regards,
Richard

[Al (astral highway)]

Have you opened it up? Many bulbs have voltage and current marked on them , so worthwhile removing the cover to inspect the bulb itself l! Then do the turns ratio calculation already mentioned above ...

[M0FYA Andy]

[See my post #4..............

[GrimJosef]

And the OP's post #10 where he says

"Unfortunately there are no bulbs".

Cheers,

GJ

[dave walsh]

Hi Richard. I'm not sure that the additional TR is such a bad idea [you seem to have a large case available-if it comes off]. I've got a few 240-120v [poss 115v] TR's [unsed and of a reasonable size] one of which might do FOC but they are only 50 c/s I'm afraid [joke] and they live in Rammy, whilst I'm "down sarf" for the forseeable. Of course it all depends on the wattage needed by the bulb but will it be that much? You might need to employ builders box TR but the death ray light doesn't look that hefty.

I've got a large industrial light [I suspect ex Salford docks boundary] that we used to illuminate the bonfire at one time! There was a huge bulb [now defunct] in a large aluminium shroud but it WAS 240v. I plugged it in with some trepidation but it worked fine. It's stripped down now and awaiting conversion into an "industrial chic" item. The "works" sealed into an epoxy filled die cast box were about 80% of the weight so it will be more manageable without that chunk.



Dave W

Bexhill

[dave cox]

Take the transformer out first. Do take some photos first so you know where all the wires go / went, as you are going to replace it anyway with a 240V you have to do this anyway

Unless there is someone nearby with measuring kit you could then post it to someone who can make the measurments safely !

dc

dc

[emeritus]

You could test it without using a transformer. Some years ago, to check if a set of UK electric hair curlers would work on 115V US mains for cousin who was abut to go on holiday there, I connected a couple of parallel-connected GLS lamp bulbs in series with the curlers, measuring the voltage to ensure that 115V appeared across the curlers (they did work OK with, as expected, an increased heating time). If you still have some old-style tungsten filament GLS lamps, then you could use the same technique: connect a number of BC lamp holders in parallel, connect them in series with the load, and add lamps until you get 115V across the equipment. You could then measure the no-load voltage across the lamp socket. It is essentially the same principle as the old use of a lamp board to charge accumulators in the days of DC mains, and the use of a resistive mains dropper in old AC/DC radios.

[YoungManGW]

Yes, it is possible to take the Lucite panels off - they are screwed to a metal frame. I have done so, and thus discovered inside the transformer and the absence of any bulbs. DaveW - maybe I'll get a cheapy 240v to 115v transformer for the moment, see how far that takes me, if that proves necessary. What I was hoping to do though was figure out the output voltage of the existing internal transformer, so that I could get a 240v to required voltage transformer, and replace the existing with that in one step. May have to do it in two steps.

Regards,
Richard