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 Post subject: Photoflash Capacitors Question
PostPosted: Jul Sat 14, 2012 2:21 am 
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Location: SOUTHLAKE, TX, USA
HI ALL:
Are Photoflash electrlytic capacitors acceptable for radio restoration purposes? What's the difference between a Photoflash and a non-Photoflash electrolytic? TIA
BOB


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Sat 14, 2012 2:28 am 
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Location: DFW Texas
Photoflash capacitors have a much lower internal resistance so they can dump their charge instantly from what I understand. Experimenters on other websites are using them for any and all uses.

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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Sat 14, 2012 2:43 am 
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Woudn't trust them. Lowest hours standards Disposable cameras are nearly obsolete . Don'd do it.


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Sat 14, 2012 2:55 am 
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Joined: May Tue 30, 2006 4:46 pm
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Location: Santa Rosa, CA
Quote:
Lowest hours standards Disposable cameras are nearly obsolete . Don'd do it.


I don't think the original poster referred to a cap from a disposable camera.

Professional strobe and flash equipment uses caps designated for hi pulse currents and fast discharge. I would guess such caps are expensive, but should be OK for radio filter applications.

http://www.hitachiaic.com/products/phot ... capacitors

Rich


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Sat 14, 2012 3:15 am 
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Location: SOUTHLAKE, TX, USA
To further clarify, the ones I'm looking at are described as used in Kodak Strobe Units. Was not aware that Photoflash caps differed depending on their application. Specifically, these are 100/330V offerred by Electonic Goldmine for what seems to be a good price (I have not looked for same specs. in my Mouser catalog).
BOB


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Sat 14, 2012 3:40 pm 
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As the saying goes, it's a short life and a merry one.


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Sun 15, 2012 3:05 am 
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Location: SOUTHLAKE, TX, USA
I imagine, based upon Alan's semi-obtuse comment, that it is not a wise idea to use Photoflash caps in radio restoration. Too bad. They are readily available (free) from those who process single use cameras.
BOB


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Sun 15, 2012 3:32 am 
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I can't recall ever having a use for a 100uf / 350 v cap in an old radio. If i did, I certainly wouldn't cobble one out of a disposable camera or dead CFL bulb with 1/8th inch leads.
If you need to save 50 cents my friend, just let me know and I'll send you a cap. You pay postage. :)

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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Mon 16, 2012 1:49 am 
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Those caps have a high ESR which doesnt affect a pulse application but when run at the listed voltage in a standard PS can heat up quite a bit from the ripple current.

The rule of thumb in HV supplies is to run at half rated voltage but monitor the case for overheating.

Carl


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Mon 16, 2012 4:34 am 
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Interesting, Mallory says they are low ESR.

Photoflash electrolytic capacitors are specifically engineered for electronic photoflash and other low impedance rapid discharge applications. Capacitors feature high instantaneous discharge currents, low leakage current, high reliability, long shelf life and low ESR.

http://www.duracap.com/electrolytic_cap ... /flash.htm


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Mon 16, 2012 7:50 pm 
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Define LOW and compared to what. That link does neither.

Carl


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Mon 16, 2012 9:15 pm 
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If Mallory says they are low ESR, I think I will have to take their word for it, unless someone can prove them wrong.

What is your definition of high ESR, please state temp and frequency also.


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Mon 16, 2012 11:56 pm 
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The data sheets don't seem to show Esr, but this app. note helps.

Looks like about 100 milliohms at 100HZ.

http://www.cde.com/tech/strobe.pdf

Rich


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Tue 17, 2012 3:30 am 
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Location: Pocasset, Cape Cod, MA
The particular ones in disposable cameras are naturally designed to be cheap, and to pack the maximum charge into a small space (as high a voltage as possible with little safety factor or surge rating). They're rated for a relatively low temperature (no one is going to be taking pictures at 85 degrees C) and they don't have to last very long.

You can probably get away with using them at half of rated voltage, but why take a chance?


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Wed 18, 2012 3:29 pm 
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Quote:
What is your definition of high ESR, please state temp and frequency also.


The accepted evaluation is temperature, if they become uncomfortable to the touch when run at full ratings the ESR is high unless you know of something else that can generate heat in a capacitor.

Carl


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Wed 18, 2012 5:25 pm 
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Location: Minnesota
Burnt Fingers wrote:
Quote:
What is your definition of high ESR, please state temp and frequency also.


The accepted evaluation is temperature, if they become uncomfortable to the touch when run at full ratings the ESR is high.

Carl


Kind of a crude way of checking ESR, that must be your "accepted evaluation" checking the ESR by feel.

Most of us will go by the manufacturers specifications and use one of the many available ESR testers.

Dave


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Wed 18, 2012 6:45 pm 
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Rediculous thread IMHO. Decent caps from reputable dealers are available cheaply and easily had. That being said, I do test them under voltage on a bridg, electrolytic or not, and do find more than 1% questionable or bad ones, which in the old days would be intolerable. Then again I do not use as many as I did a few years ago, so my occasional find of a bad one may be way off in terms of statistical significance.

Before causing more harm than good I do a reasonable amount of inspection and testing of discrete components before replacement of old ones. Good old fashioned heat absorbing clamps as used on ancient transistors (AKA Nerd Roach Clips) keep those little precision resitors in spec especially in tight quarters. Alligator clips can serve same purpose in a clinch (couldn't resist.)


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Thu 19, 2012 11:54 pm 
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Location: Central Pennsylvania
I have used photo flash grade capacitors I bought a few years ago from Electronic Gold mines in a pulse discharge service- with very high discharge currents and they have held up for three years under very light service. I have done testing consisting of 400 high intensity discharges with no noticeable problems. The caps I used may or may not be the same as the ones Electronic Goldmines is currently selling. I'd say if you want to use these for radio repair- well sure why not. The low pulse discharge impedance which may or maynot be equivalent to low ESR is not going to hurt. True photo-flash caps also have larger than ordinary internal electrical connections so that they do not open up like a fuse during short, high current discharge events.

Having said that the other commentators who caution you against the use of these caps also have a point. If you buy these caps from Electronic Goldmine you will have little or no knowledge of their background or origin. They might be really high grade, high reliability photoflash grade caps, which are worth a small fortune new intended for use in professional grade photo-flash equipment, or they might be the out of spec rejects of cheapest grade of caps intended for use in single use disposable cameras. That is how the electronic surplus market works. No disrespect to Electronic Goldmine intended.

To my way of thinking I would prefer to buy new stock caps from Mouser or Digikey made by a name brand vendor. This gives me some piece of mind I am installing quality capacitors with know origin, known specifications and know expectation of reliable service.

On the other hand if you get a great bargain on surplus caps and you are not bothered by a lack of knowledge of the capacitor pedigree, and an occasional failure will not be a problem, sure go ahead and use them.


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Fri 20, 2012 2:43 am 
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Posts: 14393
Location: Southern NH, 03076
Quote:
Kind of a crude way of checking ESR, that must be your "accepted evaluation" checking the ESR by feel.

Most of us will go by the manufacturers specifications and use one of the many available ESR testers.

Dave


Without the benefit of an expensive ESR tester that works at the caps rated voltage its a test experienced people take seriously while others are primarily keyboard experts.

YMMV based upon your lack of that experience. Manufacturers only list specs for the rated service but Im not surprised you didnt realize/understand that.


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 Post subject: Re: Photoflash Capacitors Question
PostPosted: Jul Fri 20, 2012 4:49 am 
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Location: Minnesota
Carl you never fail to amuse me. Reading your posts is better than a joke book.

Dave


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