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Chain Reaction of circumstances leads to repairs...


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#1 Alessandro Machi

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Posted 17 July 2007 - 03:58 PM

I recently purchased some new 12 V power supplies off of eBay. What I liked about them was that they had an internal quiet fan and came with a 4 pin cable.

When I tested the power supplies out I found that my voltage readings were around 11.5 volts, which made me nervous as I think lower voltage can do surreptious harm to certain equipment. The vendor tested the power supplies in their facility and claimed they were getting 12.0 volts out of the power supply. The problem with their test is if they reside in a business area the power they get may be stronger than what ends up in somebodies home.

This past weekend I fired up two HMI mini-arcs with these power supplies. I have had these 2 lights, one for about 8 years, the other one for about 5-6 years, and other than one time needing to resolder the power cord internally, they have worked pretty well.

I have a non-HMI light that runs off of 12 volt as well that actually has a volt meter built into the back of it and I put a 100W light into it, and then attached an external dichroic filter. This past Saturday the volt meter on the back of the light was showing me 11 volts. This concerned me, and although I had plenty of battery power in case I had to switch from the power supplies to the batteries, I MISTAKENLY figured that as long as the HMI mini-arc lights powered up, I would not have to worry about the lower voltage. It would either fire up the HMI light, or it would not. In addition, I should mention that the power supply outputs 9 amps.

After about 40 minutes, one of the HMI mini-arc lights starting emitting smoke from the mini-ballast located just under the light, suffice it to say it went DOA.

The other HMI mini-arc light seemed fine, so I made do with it and finished the shoot. The next day, within 10 minutes of firing up the one remaining HMI light, this time from a battery, it too went DOA.

So here's my chain reaction theory. The power supplies are made in China so perhaps they don't have the experience in making a power supply that works ideally with higher end camera and lighting gear. Instead of producing a more robust 12.5 to 13.2 voltage output, these power supplies top out at 12.0 volts when perfect voltage is coming out of a standard AC outlet. And therein lies the rub.

In Los Angeles, I think during the summer months voltage is running well below 12.0 volts. In time this could prove to be a sleazy way of selling more electricity to more people, but of inferior quality. I had a reading from this power supply in one location of 11.4 volts off of the meter on the back of the light on a Friday afternoon, and then this past Saturday in an entirely different location I was getting a reading of 11.0 volts.

I'd like to find out from those who know a lot more about electrical issues than I do if a more expensive, better made power supply can handle under 11.5 volts out of the wall, step it up to at the very least 12.0, without damaging either the light or itself.

Is there a standardized voltage cut-off point that is industry acknowledged? Is it 12.0 volts, or higher or lower than 12.0 volts? If I use a higher end power supply such as the anton bauer power supply that is a combo 1/2 battery charger and 1/2 power supply, does the anton bauer power supply achieve the higher voltage output by reducing the total wattage output it normally generates? The reason I ask is the anton bauer is supposed to output 70 watts but it shut off after a short amount of time while powering a 50 watt bulb. Could the reason be that to jump up the wall power from 11.4 volts to 13 volts it has to sacrifice some of the wattage it can output, whereas the lower cost power supply that may have had a hand in frying my light just keeps the power supply right where it is and isn't capable of adjusting upward a lower amount of voltage from the wall output?
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#2 JD Hartman

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Posted 18 July 2007 - 09:49 AM

Did the power supply supply have the word "regulated" in the description? There are different ways of achieving output voltage regulation in a DC power supply. The fact that they didn't read 12vdc on the meter under no load, would indicate that something internally isn't correct. But I don't see how a low voltage input to your 12DC HMI ballasts would ruin them, unless that caused a corresponding rise in current draw, which overloaded/fried some internal component. But that would indicate that the ballast was poorly designed as well. It should be able to deal with an input voltage that will vary as the battery discharges.
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#3 Phil Rhodes

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Posted 18 July 2007 - 11:46 AM

Hi,

> The power supplies are made in China so perhaps they don't have the experience in making a power supply that works ideally with higher end camera and
> lighting gear.

That's rather patronising.

Huge quantities of very competent and high end electronics are made in China.

But like everyone else, they're capable of building to a price.

Phil
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#4 Ralph Keyser

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Posted 18 July 2007 - 12:01 PM

Also, you might take a look at the rated current for those power supplies. Many 12v supplies are designed to drive electronics with fairly low current requirements, and your lights might be looking for more than they can provide. Well designed power supplies, however, should provide stable voltage throughout their rated load range regardless of the incoming AC voltage. Within the US, because the power systems are so widely interconnected, the standards for AC voltage and frequency are pretty tight, and the various power companies keep a close eye on each other. I doubt that your wall power is so far out of spec that it should lead to low output from the DC power supply.
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#5 John Sprung

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Posted 18 July 2007 - 12:51 PM

In Los Angeles, I think during the summer months voltage is running well below 12.0 volts.

The standard for public utilities here in California is that they are to be within 5% of the nominal voltage, as measured at the service entrance (your main breaker right after their meter). So, 114 to 126 volts is the legal range. Your building wiring, per the National Electrical Code, can drop the voltage no more than another 3% getting it to the wall socket. If that happens on one side of a shared neutral, the neutral could get pulled up 1.5% relative to the other side. So, 110.6 to 127.9 is what you should expect there.

Another thing to consider is the quality of the measuring instrument. Cheap ones may show you nice LCD digits, but not quite the same numbers as a good Simpson or Fluke.



-- J.S.
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#6 Alessandro Machi

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Posted 18 July 2007 - 06:03 PM

Hi,

> The power supplies are made in China so perhaps they don't have the experience in making a power supply that works ideally with higher end camera and
> lighting gear.

That's rather patronising.

Huge quantities of very competent and high end electronics are made in China.

But like everyone else, they're capable of building to a price.

Phil


If you noticed, I SPECIFICALLY mentioned one PARTICULAR segment of Chinese production that is made to interact with sophisticated and potentially delicate EXPENSIVE equipment.
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#7 Alessandro Machi

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Posted 18 July 2007 - 06:29 PM

Did the power supply supply have the word "regulated" in the description? There are different ways of achieving output voltage regulation in a DC power supply. The fact that they didn't read 12vdc on the meter under no load, would indicate that something internally isn't correct.


The light that has the built in volt meter only gives me the voltage when the light is on, and it's not a digital readout but an analog readout with an actual needle that with a range of 10.0 to 15.0 volts. It seems to be pretty accurate, when I hook up a dionic or an anton bauer power supply the needle goes to between 13.0-14.5, when I use deep cycle lead acid batteries it reads 12.5-12.8 on the high end, then settles in around 12.0 for a quite while. I didn't have a way to actually measure the power supply with no load, but the power supply can output 9.0 Amps, so a 24 Watt HMI mini-arc should be well within what it can handle.

The specs on the power supply are... AC INPUT 100-120V/200-240V ~ 50-60HZ 3.0A/1.5A, DC Output +12V---9.0A

There's also another place where it states all of the above plus 230-286 VA.


But I don't see how a low voltage input to your 12DC HMI ballasts would ruin them, unless that caused a corresponding rise in current draw, which overloaded/fried some internal component. But that would indicate that the ballast was poorly designed as well. It should be able to deal with an input voltage that will vary as the battery discharges.


Yeah, I think this is the crux of the issue. The question is, just how low and for how long should a ballast "tolerate" lower voltage? When I use batteries to power the lights, perhaps they eventually output voltage as low as this power supply, but they started with higher voltage and it's just a relatively short time in which they are at the lowest voltage before the light shuts off, whereas with the power supply, it apparently outputed low voltage for a long enough period of time to damage an internal component.

----------------------------------------------------

Follow up question, lets say later versions of this same light handle lower voltage better, does a lower voltage still eventually affect the internal component no matter how well it is re-designed? And if the answer is yes, does that then mean there is a voltage cut-off point that ensures the internal components will last longer?
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#8 Alessandro Machi

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Posted 18 July 2007 - 06:37 PM

The standard for public utilities here in California is that they are to be within 5% of the nominal voltage, as measured at the service entrance (your main breaker right after their meter). So, 114 to 126 volts is the legal range. Your building wiring, per the National Electrical Code, can drop the voltage no more than another 3% getting it to the wall socket. If that happens on one side of a shared neutral, the neutral could get pulled up 1.5% relative to the other side. So, 110.6 to 127.9 is what you should expect there.

-- J.S.



I'm assuming I just move the decimal point over one spot from the numbers you provided.

So if the back of my light was reading 11.0 volts, and I know there is a drop of about .2 to .25 volts that was directly related to the length of 4 pin cable run from the power supply to the light that I was using, would 11.25 volts out of the wall socket fall within the acceptable range?

-------------------------------------------------------------------------

So perhaps this was a combination of two older lights that probably have somewhat worn down internal components that have lost some of their tolerance for lower voltage as time goes on?
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#9 John Sprung

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Posted 18 July 2007 - 07:09 PM

I'm assuming I just move the decimal point over one spot from the numbers you provided.

So if the back of my light was reading 11.0 volts, and I know there is a drop of about .2 to .25 volts that was directly related to the length of 4 pin cable run from the power supply to the light that I was using, would 11.25 volts out of the wall socket fall within the acceptable range?

-------------------------------------------------------------------------

So perhaps this was a combination of two older lights that probably have somewhat worn down internal components that have lost some of their tolerance for lower voltage as time goes on?


Yes, 112.5 Volts at the wall socket would be OK by the Public Utilities Commish and NEC.

As for tolerance for lower voltage, most things have no problem with it. The exceptions are inductive things, like motors, transformers, and some ballasts. To get the same power at a lower voltage, they have to draw more current, which makes them run hotter. Motors in particular are much more forgiving of a little higher voltage than a little lower. That's why they're often rated for less than the nominal supply, like 115 instead of 120. Incandescent lights are the opposite, no problem with under voltage, much shorter life on over voltage.



-- J.S.
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#10 Alessandro Machi

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Posted 18 July 2007 - 11:24 PM

Yes, 112.5 Volts at the wall socket would be OK by the Public Utilities Commish and NEC.

As for tolerance for lower voltage, most things have no problem with it. The exceptions are inductive things, like motors, transformers, and some ballasts. To get the same power at a lower voltage, they have to draw more current, which makes them run hotter. Motors in particular are much more forgiving of a little higher voltage than a little lower. That's why they're often rated for less than the nominal supply, like 115 instead of 120. Incandescent lights are the opposite, no problem with under voltage, much shorter life on over voltage.
-- J.S.


Could be time for a whisper quiet mini-fan installation in these units.
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#11 JD Hartman

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Posted 19 July 2007 - 09:18 AM

Without trouble shooting both the 12v ballasts and determining what components that failed, all the posts on this thread are simple conjecture. If you knew the failure mode of the ballast(s), you would have some clues, indicating what was wrong with the power supplies. Taking one last guess, if due to poor design, the power supply failed to hold the output voltage steady at 12vdc, it might also be deficient in filtering the AC ripple component from the DC output. You would need an oscilliscope to view the waveform of the power suppply. In theory DC would appear as a flat line above the 0v point on the scope. The amount of AC ripple in the output would be clearly visible as a jagged line. This AC residue may have damaged your ballast.
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#12 timHealy

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Posted 19 July 2007 - 09:43 AM

best

Tim

Edited by timHealy, 19 July 2007 - 09:44 AM.

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#13 Alessandro Machi

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Posted 19 July 2007 - 09:47 AM

Without trouble shooting both the 12v ballasts and determining what components that failed, all the posts on this thread are simple conjecture. If you knew the failure mode of the ballast(s), you would have some clues, indicating what was wrong with the power supplies. Taking one last guess, if due to poor design, the power supply failed to hold the output voltage steady at 12vdc, it might also be deficient in filtering the AC ripple component from the DC output. You would need an oscilliscope to view the waveform of the power suppply. In theory DC would appear as a flat line above the 0v point on the scope. The amount of AC ripple in the output would be clearly visible as a jagged line. This AC residue may have damaged your ballast.



I have sent both lights in for repair and I'll share the results once I know what they are.
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#14 Alessandro Machi

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Posted 19 July 2007 - 09:52 AM

...Taking one last guess, if due to poor design, the power supply failed to hold the output voltage steady at 12vdc, it might also be deficient in filtering the AC ripple component from the DC output. You would need an oscilliscope to view the waveform of the power suppply. In theory DC would appear as a flat line above the 0v point on the scope. The amount of AC ripple in the output would be clearly visible as a jagged line. This AC residue may have damaged your ballast.


Would a volt meter reveal the AC ripple that you speak of, and if the answer is yes, should I assume that it would be a volt meter that meters to a hundreth of a volt versus a tenth of a volt?
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#15 JD Hartman

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Posted 19 July 2007 - 11:34 AM

I don't recall there being any meter that will do so. If the ballasts are in a local shop, bring one of the power supplies with you when you pick them up. They may be willing to show you what its output looks like on a 'scope.
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#16 John Sprung

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Posted 19 July 2007 - 12:14 PM

Would a volt meter reveal the AC ripple that you speak of, ...

Sure -- All you have to do is clip together a little RC filter to block the DC and let you read only the AC. Better yet, look at it on a scope and see if the ripple is sinusoidal at 50/60 Hz from the line, or a higher square wave frequency from duty cycle regulation. Volt meter values would only be valid for sine wave AC.



-- J.S.
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#17 Alessandro Machi

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Posted 23 July 2007 - 04:24 PM

I just did a quickie test on the power supply. I'd like to see how others interpret the test and my interpretation of the test as well.

I hooked up a 100 Watt light to the 12 volt power supply and the voltage meter on the the back of the light was showing about 11.1 volts.

I then changed out the light with a 35 watt bulb, and the same voltage meter was showing me 12 volts spot on.

So somewhere between 35W and 100W there is a drop off in voltage of around .9 volts. Since the
power supply is rated for 9 amps, doesn't that pretty much indicate that this is in fact not a 9 amp
power supply since the voltage begins dropping somewhere just after 35W? Am I correct in simply
taking 35/12 to get an amperage rating of just under 3.0A?

If yes, then the power supply may output 9amps, but it may be that only the first 3 amps that can be trusted
as maintaining a 12 volt output out of the wall, is that a correct interpretation on my part, and is is common for
a power supply to work that way?
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#18 Richard Andrewski

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Posted 24 July 2007 - 12:48 AM

So here's my chain reaction theory. The power supplies are made in China so perhaps they don't have the experience in making a power supply that works ideally with higher end camera and lighting gear. Instead of producing a more robust 12.5 to 13.2 voltage output, these power supplies top out at 12.0 volts when perfect voltage is coming out of a standard AC outlet. And therein lies the rub.


Your theory doesn't hold. Higher end camera and lighting gear have the same requirements as lower end. They all need a certain voltage range to run in. Your high end gear is not so great if it can be damaged by a bit of underpowering--say at 11.5vDC rather than 12vDC. In addition, a drop in the wall voltage to even 90 VAC won't affect most DC power supplies. The reason their output voltage drops is not because of input AC voltage drop but because there is too much draw on their output--beyond their specs. If the input AC voltage drops too much, they'll likely just shut down and not output any power rather than lower the output. Your 9 amp power supply may indeed not be really rated for 9 amps so they fried with too much wattage draw placed on their output beyond their real tolerance level.

As far as China goes, you can get whatever quality level you like or are willing to pay for from China. I manufacture stuff regularly here and have no problems but then I specify in great detail. A great portion of the world's fluorescent ballasts are made here now so your theory is far off base. You can buy a cheap power supply made in China that doesn't hold the proper output because its regulator won't hold and you can find one made in the USA also. All depends upon design and components and you can get bad designs or components anywhere.

In Los Angeles, I think during the summer months voltage is running well below 12.0 volts. In time this could prove to be a sleazy way of selling more electricity to more people, but of inferior quality. I had a reading from this power supply in one location of 11.4 volts off of the meter on the back of the light on a Friday afternoon, and then this past Saturday in an entirely different location I was getting a reading of 11.0 volts.

I'd like to find out from those who know a lot more about electrical issues than I do if a more expensive, better made power supply can handle under 11.5 volts out of the wall, step it up to at the very least 12.0, without damaging either the light or itself.


I think you're mixing things up here. The voltage out of the wall is not 12v DC, its in a range from 90 to 130 or so volts of AC. As noted before, most equipment these days can adapt as can most power supplies.

Many fluorescent or HMI ballasts for instance can run in this range with no problem. Many universal voltage ones can run from 90 to 277v and automatically adapt. Mosts ballasts are AC input but your HMI's are DC input from what you've said so they can run off batteries. A DC ballast that can't run in a certain range of DC voltage is not a great ballast and I wouldn't categorize this as high end at all.

Is there a standardized voltage cut-off point that is industry acknowledged? Is it 12.0 volts, or higher or lower than 12.0 volts? If I use a higher end power supply such as the anton bauer power supply that is a combo 1/2 battery charger and 1/2 power supply, does the anton bauer power supply achieve the higher voltage output by reducing the total wattage output it normally generates? The reason I ask is the anton bauer is supposed to output 70 watts but it shut off after a short amount of time while powering a 50 watt bulb. Could the reason be that to jump up the wall power from 11.4 volts to 13 volts it has to sacrifice some of the wattage it can output, whereas the lower cost power supply that may have had a hand in frying my light just keeps the power supply right where it is and isn't capable of adjusting upward a lower amount of voltage from the wall output?


It all depends upon the watt hour rating of the battery. 70watts for how many minutes or hours? You have to know that rating as just wattage alone doesn't tell you enough to know if a battery will do what you want it to do. The charger should be able to handle fluctuations in input AC voltage within normal tolerances of 90 to 130v or so and that shouldn't affect output at all if the input stays in that range.

Edited by Richard Andrewski, 24 July 2007 - 12:51 AM.

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#19 Richard Andrewski

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Posted 24 July 2007 - 01:02 AM

I just did a quickie test on the power supply. I'd like to see how others interpret the test and my interpretation of the test as well.

I hooked up a 100 Watt light to the 12 volt power supply and the voltage meter on the the back of the light was showing about 11.1 volts.

I then changed out the light with a 35 watt bulb, and the same voltage meter was showing me 12 volts spot on.

So somewhere between 35W and 100W there is a drop off in voltage of around .9 volts. Since the
power supply is rated for 9 amps, doesn't that pretty much indicate that this is in fact not a 9 amp
power supply since the voltage begins dropping somewhere just after 35W? Am I correct in simply
taking 35/12 to get an amperage rating of just under 3.0A?

If yes, then the power supply may output 9amps, but it may be that only the first 3 amps that can be trusted
as maintaining a 12 volt output out of the wall, is that a correct interpretation on my part, and is is common for
a power supply to work that way?


Running a 100w 12VDC light off that power supply is darn close to the rating. 100/12 = 8.3 amps. That's not so far from the top end. But its not abnormal for a 12VDC power supply to operate in a range. As I said in my previous reply here, if your DC input ballasts on the HMI's couldn't handle the range of input voltage, they're not all that great. By the way, you never mentioned what the wattage of your DC HMI's is did you? Maybe I missed it. It's pretty relevant. If they were 100w then you've got the same 8.3a draw as the other 12v light you mentioned. If its 150w then you have a 12.5a draw, etc. If your running your DC power supplies over the 9a rating then you've got serious problems and its not unbelievable that you fried the ballasts as you may have damaged the regulators on the supplies (although usually they shut themselves down though before they can do serious harm to anything).
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#20 Alessandro Machi

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Posted 24 July 2007 - 05:25 AM

The HMI lights are 24 watts and I think they need about 28 watts to operate. They do need a lot more punch to get going however so a 3 amp power supply will not fire them up.

When I was stating 12 volts I was referring to the reading I was getting from the power supply to the light, I didn't mean to imply that the voltage coming out of the wall was 12 volts.

It seems like the industry in general likes above 12 volts rather than below. 13.2 volts seems to be the new 12 volt for different applications. Anton Bauer supports 13.2 volts.

As the voltage drops below 12 volts, some equipment seems to be more susceptible to "browning out". Maybe it would be correct to say that "older equipment" is susceptible to browning out as the voltage drops?
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