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BetterSense
9-Oct-2012, 17:20
I have a flash system that has had a broken flash tube since I bought it. I bought a new tube for it and soldered it in, but it doesn't flash. It's possible that I got a bad tube, but it could also be something else. But there's not a whole lot else--just some resistors, a cap, and some weird cardboard coil thingy.

I'm suspecting that brown cardboard coil thing. I have no idea what it is but it looks like a coil of some kind. Maybe the electrolyte is dried out or something? Does anyone know what it's for?

photobymike
9-Oct-2012, 17:32
LOL bettersense.... be careful !! The voltage from these units will stop your heart.. literally... i work with my dad when i was a kid as a electrician helper... i have seen a fellow worker killed from electrocution. It was from hi amperage ... but the right hi voltage can stop your heart. It seems to me that it would be cheaper to buy a used working head.... just my humble opinion...

BetterSense
9-Oct-2012, 17:49
Don't worry; I'm a professional. I just don't know what I'm doing.

Leigh
9-Oct-2012, 17:52
II'm suspecting that brown cardboard coil thing. I have no idea what it is but it looks like a coil of some kind.
That's the trigger transformer. It's probably open. Fairly common problem, not related to the broken flash tube.

I suggest you send it to Novatron for repair.

- Leigh

ic-racer
9-Oct-2012, 18:12
http://www.ebay.com/itm/Trigger-coil-transformer-for-Flashtube-flash-tube-xenon-/110632978524?pt=LH_DefaultDomain_0&hash=item19c23d485c

$3.30

Scott Davis
9-Oct-2012, 18:53
I'd suggest skipping DIY fixes with strobe gear, ESPECIALLY Novatrons. They have a reputation for unintended discharges with less than fortuitous outcomes.

Leigh
9-Oct-2012, 19:16
Yeah, what he said ^^^^

Do not try to fix this yourself. You don't have the schematic, and Novatron won't give it to you, nor will they sell you parts.

The trigger transformer on ebay (linked above) is NOT the correct transformer for your head.

As i said before, send it to Novatron or an authorized service shop for repair.
I used to be a warranty service station for Novatron, so I'm reasonably familiar with their products.

- Leigh

Cletus
10-Oct-2012, 06:08
Just my two bits - because I'm bored and don't feel like working this morning - I am an electrical engineer and an experienced electrician to boot, and I wouldn't be fooling around with something with that much potential (literally) to do serious bodily harm. No matter your deep knowledge of tracing out circuits without a print, 'discharging' caps, grounding, etc., 500 to 1000v stored up in enough uFs is EASILY enough to KILL you.

I'm sure your head is disconnected from the source and you have no intention of....whatever. When you're troubleshooting, replacing parts and doing what you're doing, there will eventully come a point where you are at HIGH RISK of exposure and it ain't worth it!

Last thing I'll say, then quit my little warning lecture: I thought I was in high cotton, years ago, trying to "fix" an itty-bitty electronic flash unit. (Not a great big power pack unit) I was alone and evidently came into contact with an itty-bitty, harmless looking little cap. I'll never be sure what happened exactly, but I got up off the floor, missing nearly four hours and with absolutely no memory of what happened. I can only believe that I truly have a guardian angel and he was present and accounted for that day.

photobymike
10-Oct-2012, 08:29
I tried to warn ... even experienced people say its not worth it.... depending on your condition and circumstances we may be minus a LF member. I tried to fix a flash head long ago.... i plugged into the pak and blam !! the power pak blew up ..

oh well keep us up to date please.....

E. von Hoegh
11-Oct-2012, 07:02
Fools rush in, where wise men fear to tread....

One way to be certain would be to solder a jumper across the capacitor while you are working on the unit. Be sure to discharge the cap. first. The jumper is important because hysteresis of the electrolyte can allow the cap. the build up a charge all by itself, after you've discharged it.
That said, listen to everyone else and don't mess with it unless you know exactly what you are doing.

Leigh
11-Oct-2012, 07:57
One way to be certain would be to solder a jumper across the capacitor while you are working on the unit.
E.,

That's the stupidest idea I've ever heard.

Shut up before you kill somebody.

You have no clue what you're talking about!

- Leigh

E. von Hoegh
11-Oct-2012, 07:59
E.,

I suggest you shut up before you kill somebody. You have no clue what you're talking about!

- Leigh

Did you read the rest of my post? Where I said to discharge the thing first? At least this would allow the OP to replace other parts without danger.

And kindly tell me why this is a stupid idea.

Bob Salomon
11-Oct-2012, 08:11
Add my two cents. A friend was the factory service technician at Norman many years ago and he had a bad scar on a finger where he accidently discharged a cap in a head while servicing it. The damage went in one side of his finger and came out the opposite side. Scars on both sides. Not pretty and it was his job to repair them.

When I sold Rollei Studio Flash Systems; 250ws, 1250ws and 5000ws units I was demoing a Rollei E5000 unit (5000ws, required 220V 3 phase AC) at Armstrong Industries in Lancaster, PA. On the third shot the unit blew up because what they thought was a 220V line was actually 440V. Unit flew across the studio and crushed itself against the far wall. There is tremendous power stored in fully charged caps. Not a DIY project. Even if you think you are trained.

Cletus
11-Oct-2012, 08:28
Exactly! There are very specific procedures for discharging high energy caps and "sticking a wire across the terminals" is likely to result in an explosion in your face. At the very least, a resistor (or some unknown value) needs to be included in the discharge circuit and there's most definitely the potential for a hysteresis charge building back up in the cap after it's been discharged if this isn't done correctly, or the wrong value resistor is used in the discharge circuit.

Add that to the fact there are probably many caps in a Novatron pack arranged in an array, so it's more than just a simple matter of "jumping out a cap" to make it safe. And most dangerous of all, at some point, the repairer will need to power everything up again, which presents yet another risk of deadly electric shock or explosion if something hasn't been done correctly, or some value has been changed - say, installing an unknown inductor in a head, or something like that.

Bottom line - too risky to fool with and for the $60 a good used head is likely to cost, it's not worth it!

Leigh
11-Oct-2012, 08:30
Did you read the rest of my post? Where I said to discharge the thing first? At least this would allow the OP to replace other parts without danger. And kindly tell me why this is a stupid idea.
I'll repeat my previous post.

YOU DON'T KNOW WHAT YOU'RE TALKING ABOUT.

- Leigh

E. von Hoegh
11-Oct-2012, 08:30
Fools rush in, where wise men fear to tread....

One way to be certain would be to solder a jumper across the capacitor while you are working on the unit. Be sure to discharge the cap. first. The jumper is important because hysteresis of the electrolyte can allow the cap. the build up a charge all by itself, after you've discharged it.
That said, listen to everyone else and don't mess with it unless you know exactly what you are doing.

There, for those who cannot be bothered to read.

Cletus
11-Oct-2012, 08:31
My last point - which everyone knows already anyway - these studio strobe packs are designed to release VERY large amounts of energy in MICROSECONDS! Think about that!

rdenney
11-Oct-2012, 08:53
E.,

That's the stupidest idea I've ever heard.

Shut up before you kill somebody.

You have no clue what you're talking about!

- Leigh

It's not that dumb, but I agree it is potentially dangerous advice, because the precondition to installing that jumper (full discharge) is not at all trivial, no matter how much E.v.H. boldfaces it.

Large amateur radio amplifiers that use vacuum tubes that are biased by high-voltage power supplies that have huge filter capacitors use two strategies to discharge and then ensure that the caps and tubes stay discharged: They use a large ballast resistor, of sufficiently high resistance not to undermine the voltage being supplied during use, to bleed off residual charge. And then they have a mechanical shorting bar that collapses onto the high-voltage bus when the case is opened. The voltage in question for those amplifiers is usually in the 2000-3000V range for equipment radio amateurs use.

Not all of them have the shorting bars, but they all have the bleeder resistors.

Sometimes those resistors are opened, and sometimes the diode strings used to rectify the power supply output are opened. In those cases, the charge may not be bled off. The shorting bars are deep inside the case and short long before one's hands can get near it, but a significant discharge using the shorting bar is still a memorable event that can cause further ruination. The power head for a studio flash system is just not much different at all from the power supply used for a radio amplifier. My Speedotron power head has bleeder resistors, and after a minute or two the capacitors require a complete recharge when the head is next turned on. But portable flashes usually hold the charge to minimize battery consumption and don't have bleeder resistors.

The standard tool for ensuring that the charge is bled off is to use a "chicken-stick", which is a probe with a high-dielectric insulator about a foot long as a handle. It has a metal tip that is grounded by means of a jumper wire. It's a safety device intended to be used only after an orderly discharge of the capacitor, however, like the shorting bar. I measure the voltage at the danger points using a 6000-volt probe (which cost more that the Fluke meter it connects to), but if there is high voltage present, there's a real question about how to get rid of it.

And therein lies the danger. Discharging a capacitor suddenly might have really spectacular results, including spraying bits of it all over the room. And the tool used to discharge it works because it provides a path to ground for those hundreds or thousands of volts, with the attendant risk that the person holding that device is in that path.

The injury severity issue is related to how much of a person is in that path, and that's what will determine the damage it does. Bob's technician acquaintance demonstrates what one finger in the path means. Most apply the "one-hand" safety technique, to minimize the probability that the really important bits (heart, etc.) are in the path, but it's not easy to predict what that path will be or what part of the body found itself unintentionally attaching to the ground path. I was fiddling with a Rollei potato-masher flash some many decades ago, and got just a part of the jolt from the flash capacity as I was attempting to discharge it using a probe. I was heavier than the flash so it was the flash unit that took the horizontal trajectory to the far wall. But the muscles in that arm were sore for several days.

The danger, then, is that 1.) it isn't easy or obvious to discharge a capacitor of that size, and 2.) if one does not know or have a way of measuring the charge state, there is considerable risk resulting from placing that shorting jumper across the capacitor leads before soldering it. And the consequences of a mistake are potentially severe.

The correct way is using a hi-pot probe with a discharging bleeder resistor to measure the drop in voltage until it reaches something safe to handle (under 40-50 volts with dry fingers).

Rick "properly afraid of high-voltage work" Denney

Leigh
11-Oct-2012, 09:02
Discharging a capacitor improperly can KILL you.

IT WILL EXPLODE.

E. It's obvious you're more concerned with your own ego than with the safety of other members.
You should be ashamed of yourself.

- Leigh

E. von Hoegh
11-Oct-2012, 09:59
Discharging a capacitor improperly can KILL you.

IT WILL EXPLODE.

E. It's obvious you're more concerned with your own ego than with the safety of other members.
You should be ashamed of yourself.

- Leigh

Fine. I'll never comment on anything potentially dangerous again, since too many are willing to read parts of a post and ignore other parts.
I hadn't noticed anyone mention the fact that hysteresis in the dielectric/electrolyte can cause the capacitor to "recharge" itself and deliver a nasty shock - or much worse in the case of a studio flash. Temporarily shorting a high voltage/high capacity capacitor is the only way I feel safe around one, it's not unheard of for them to build a charge from static electricity while on the shelf.
I had assumed that my final sentence was warning enough to anyone with the ability to read.

Rick, thanks for pointing out the use of bleeders and chicken sticks.

Once again, as I wrote in my first post: "That said, listen to everyone else and don't mess with it unless you know exactly what you are doing".

Cletus
11-Oct-2012, 10:23
I don't think anyone should be arguing or putting anyone else down over this. I'm pretty sure the OP got the point and either chose to take the advice here, or not.

Either way - and I'm afraid I contributed to this too - there's no reason to continue this pissing contest over who knows (or thinks they know) more about capacitors and the hazards of working with them, then the other. There are many ways to skin a cat and everyone's experience is different. I don't think anyone's advice to the OP was intended to do anything other than dissuade someone from getting into something that could seriously injure, or kill and it seems that was accomplished.

Personally, I've never even seen the inside of a Novatron pack, so I should have probably cooled it on all my righteous "advice" a while ago. I just know that capacitors can be dangerous to work around, even when you do know what you're doing, and leave it at that.

(listen to be being all diplomatic...I'm sure I'll catch hell for that now!)

BetterSense
11-Oct-2012, 10:36
Did anyone read my original post? I'm not messing with the pack. I'm only working on the head, which has one measly 100uF capacitor in it.

Leszek Vogt
11-Oct-2012, 10:44
Although I've heard about the dangers of messing with flash units, at least in anecdotal sense, it's helpful to have this discussion. Perhaps I should add:minus the chest thumping. Appreciate the info.


Les

Steve Smith
11-Oct-2012, 11:07
I'm only working on the head, which has one measly 100uF capacitor in it.

Do you mean 100nF rather than uF?


Steve.

Cletus
11-Oct-2012, 11:33
BetterSense -

Against my better judgement, I'll chime in one more time. I think everyone understands you're just working on the head and not the pack. This discussion spun out of control awhile ago, including me and with varying degrees of knowledge and experience, chiming in their two bits about how risky it is to work on studio strobe gear in general and the inherent dangers of capacitors.

In my opinion, which really is NOT an expert one, despite my earlier remarks, the danger lies when you start plugging in the head and testing it after your repairs. Or also, as Rick Denney mentioned, the chance that there is another capacitor in the head that you may have overlooked that could store up quite a wallop. You said there is a 100uF cap in the head, which is more than enough, depending on the voltage (the rating printed on cover notwithstanding) to deliver a pretty serious electric shock.

Also, if something doesn't work as expected, or even if not, there's still a considerable risk of shock when charging the pack, plugging and unplugging the head to take it apart again, etc. On top of that, the fact that Novatrons are (from what I've read and heard) notorious for discharging unexpectedly - especially if it decides to discharge, at any time, to the case or the metal head plug with you electrically connected to it!

Just be careful and good luck getting your head working...

Steve Smith
11-Oct-2012, 12:03
You said there is a 100uF cap in the head, which is more than enough, depending on the voltage (the rating printed on cover notwithstanding) to deliver a pretty serious electric shock.

If it's that dark red component in the pictures, it's either 100nF rather than 100uF or it's of a fairly low voltage.


Steve.

Steve Smith
11-Oct-2012, 12:04
I suspect that as the trigger capacitor is in the head, then the capacitor which is discharged into it to create the triggering pulse is also in the head and this is it. If so, it will be in the 10nF to 220nF range.

Whilst this capacitor can also charge up to a couple of hundred volts, the energy stored is small. It does no harm to the contacts in a shutter.


Steve.

E. von Hoegh
11-Oct-2012, 12:09
Although I've heard about the dangers of messing with flash units, at least in anecdotal sense, it's helpful to have this discussion. Perhaps I should add:minus the chest thumping. Appreciate the info.


Les
Too bad they don't get so upset about driver safety, or the importance of being an informed voter.

jnantz
11-Oct-2012, 13:28
hi bettersense

you might consider just sending the light to novatron ( they are in TX )
getting it repaired by them, or getting a refurbished one
directly from them, they are pretty inexpensive and will have a warrantee .
the batter pack novatrons don't really put off very much light from what i remember,
at least the old ones that were like 200WS split between 4 heads ...

good luck!
john