Danger of using old strobes?

[argos33]

I've always heard that old strobes can be very dangerous but cannot remember exactly why. Is it just because they do not have as many safety features preventing accidental shock? Or because cords can get old and expose wires, etc? Anyone want to shed some light on the issue?

I am thinking about playing around with an old 800W speedotron and well....don't want to die.

Thanks for any input/advice

Evan

[Peter De Smidt]

Well, any of the electrical or mechanical parts can go. Seeing one start arcing can be quite the sight. Black line packs are very rugged, although I don't know if that's what you have. I've used some that are older than me, and I'm not that young Look for areas of damage, especially around the sync plug and the plugs for the heads. If there is some, get it fixed. Be careful when you turn it on.

Never unplug/or plug in heads with the power on with Speedo equipment.

[Richard Wheat]

I use three old flash units fairly regularly for extra fill. As far as I know, old strobes can be dangerous for three reasons.

A) the general electrical condition of the unit - eg. frayed power cords, earthing, damage to the unit which may have compromised its electrical saftely, etc.

B) the trigger voltage present

C) the condition of the flash tube

The first can be mitigated by submitting the unit to an electrical safety test and inspection. In Australia you could have the unit certified electrically safe against an Australian standard.

The second is only a problem if you are using modern electronic equipment to trigger the flash - eg. a digital SLR - and in this case you can obtain some sort of slave circuit to go inbetween which can handle the high voltages present. Just don't connect an old strobe directly to a modern camera. I have made a couple of circuits to go inbetween modern cameras and old strobes - they are quite simple - but you need to get them right.
If you are triggering directly from a large format mechanical shutter - no problem. As these are a mechanical switch, there is no danger from a higher trigger voltage.

The third I have no experience with but I believe that older flash tubes are liable to explode.

I also understand that an older flash tube may give you a different temperature of light - ie. one that you may find it hard to balance with a 2nd unit. I have never had this problem though. I use two modern Bowen heads with three old Courtney units and have not had any problem.

Hope this helps,
Richard.

[Jason Greenberg Motamedi]

The capacitors of any flash unit can carry enough power to kill, even when unplugged. Never open a power supply unless you know what you are doing. From what I understand, the newer ones automatically discharge the capacitors once turned off.

[Kirk Gittings]

Not sure what you mean exactly by old. I use

old strobes

weekly. 30 year old ones to be exact. Many of them I am the original owner. Old Normans actually. Like my old bones, they work fine with a little TLC. Hear a weird noise? Smell something funny? Run it in to the repair place.

[ic-racer]

Not sure about old strobes in particular, but the thing to remember with any strobe is that unlike a regular light bulb, the voltage is already applied to the leads of the bulb before you turn it on.

[Frank Petronio]

I've regularly used unmaintained cheap beater ca. 1979 Dynalites without problems.

What happens with a lot of older strobes is the connectors will get compromised or some fool will unplug a live cable from a pack and you'll get arcing and explosive discharges that will send the cable through drywall on the other side of the studio (or through you...) Speedotrons, Ascors, Normans are all noted for this.

I think the European and Asian packs are safer in this regard but it's a good habit to turn them off before swapping cables no matter what.

[Struan Gray]

I have an old Courtenay unit that I regard with deep suspicion, but which has yet to give any trouble. Golden rules seem to be to turn it off before plugging or unplugging anything, and to let it discharge for a long time connected to ground before doing any McGyver stuff with the case open.

In fact, unless you have a background in electronics, and high-voltages at that, I would say don't ever take the top off. The capacitors are lethal for some time after turning off, and they're more lethal than other commonly available HV sources like vacuum-tube TV screens. Proper repair shops have a shunt to discharge them safely, but it's not something you want to jury-rig.

If you do have electronics experience it's worth having a look inside because the capacitors are the elements that are most likely to have gone wrong in long-term storage. Check them over carefully for any signs of leakage or corrosion.

That said, the only bad point on mine was the lead that connected the pack to the head. The insulation was completely shot - dry, hard, cracking - and it obviously had to be changed. The plugs were also brittle, but they were commonly-available valve-base plugs so were easy to find replacements. If you have, or can get hold of, a HV insulation tester, it would be well worth checking your cables.

[Sascha Welter]

Broncolor units have a flap over the cable connectors. When you lift the flap to swap a cable, the unit is turned off. Of course... lift it just a little bit and wiggle the cable and you will be able to disconnect the cable with the unit still on. Wiggle space probably gets worse as they get older.

[rdenney]

I've never opened my Speedotron 1600. But the general theory behind fixed-ouput strobes is that they charge a very large electrolytic capacitor, and the discharge it into a xenon tube at very high voltage.

The danger is in the electrolytic capacitors. A capacitor is a storage device for electrical charge, and it can store that charge for quite a while. The charge that can be stored by the large capacitor in a flash unit (or in power supplies for devices that use vacuum tubes that require a very high biasing voltage) can kill you. Do not work on one unless you know what you are doing, such as how to discharge a large cap with a grounded high-voltage probe. They may be equipped with bleeder resistors, and the cases may have a shorting bar for safety. If you don't know what those are, step away from that screwdriver.

The electrolytic capacitors can also die of old age. They work by coating aluminum foil with a layer of oxide that acts as a dielectric, and then rolling it up so that the dielectric is between layers of the foil. They require a basic voltage to be applied to maintain the oxide layer. When they are left unpowered for very long periods, that dielectric layer can sometimes degrade, which allows the layers of the foil to touch, shorting out the capacitor. This results in a loud bang, followed by the release of smoke. The smoke cannot be reinserted, unfortunately. But you'll know if this is a problem--just set the power unit (no heads plugged in) in the middle of your garage, walk away from it, and then plug it in. If the cap is shorted, you'll hear and see the problem. Send it to Mr. Speedotron to have the smoke replaced.

If you don't get fireworks, then just let it sit, powered up, for a couple of days, and it should be good to go. If you haven't bought the unit yet, ask for a demonstration. If it works in the demo, then you should be good to go, at least as regards the electrolytic capacitors.

Very old capacitors used waxed paper as the dielectric, and those dry out and short. But I am sure that predates any electronic flash system.

The trigger voltage on these is about 300 volts. Speedotron makes a low-voltage switch interface that you should buy before using this with any electronic camera, though it should be fine with mechanical view-camera shutters. That device is only about a 1" cube and plugs into the dual-spade receptacle for the sync cable. Note on that receptacle: It looks like a regular 120VAC plug. BUT IT ISN'T. Confusing the two can have disastrous consequences. I bought one of those interfaces from B&H a few years ago and have used my 1600 Brown Line head with digital cameras with no issue. Install that device and leave it--it will work fine with all shutters.

I would not worry about the flash tubes. I suppose they can get old and gassy, but I've never seen it and mine are still perfect even after periods of both intense use and inactivity. Also, the tube itself is enclosed in a glass enveloped that will at least eliminate any reference to the word "shrapnel". Flash tubes can always burn out, though. Tubes for the MW3R and the M11 heads are still made and available from B&H, as are all the accessories for both the Brown Line and the Black Line. But if your power supply is an 800WS model, I'd be willing to bet it's a Brown Line.

Finally, check the extension cords for the heads. If they are cracked, replace them. They carry high voltage and cracks will give that voltage a place to leak out if there is something attractive (like your hand) to leak to.

Rick "whose Speedotron 1600 system has been a real workhorse" Denney