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Apparent mismatch of socket with GE#5 bulb adapter
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Henry



Joined: 09 May 2001
Posts: 1442
Location: Allentown, Pennsylvania

PostPosted: Mon Mar 03, 2008 10:08 pm    Post subject: Reply with quote

I used to fire 5B bulbs reliably in my Ultima flash with folding reflector, using a 22.5 volt battery, Mallory M-215. The equivalent battery is available today from Radio Shack, Eveready M412, rated at 140mAh. I don't think current supply would be a problem with the 3x9v cells I'm envisioning!

Incidentally, that Mallory M-215 lasted forever. I must have fired off several dozen bulbs over a period of several years, and it just wouldn't quit. That's not heavy use, I admit, but believe it or not I still raise a tickle on the voltmeter with it today.
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Polaski



Joined: 06 Jun 2005
Posts: 21
Location: Philadelphia, PA

PostPosted: Tue Mar 04, 2008 1:12 pm    Post subject: Ag1's Reply with quote

I checked last night, and the Minox flashes use a 15v battery. The original is of course no longer available, but good old Radio Shack has equivilents.

And of course the Minox flashes were designed for AG1 bulbs, although I saw one recently that has a fan reflector much like that of the Tilt-a-Mite.

It's a bit odd that I am in this discussion, since I almost never depart from available light. It's just that using this old technology makes me smile.
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robcruickshank



Joined: 25 Feb 2008
Posts: 19
Location: toronto, canada

PostPosted: Wed Mar 05, 2008 7:17 pm    Post subject: Reply with quote

The problem with using 9v batteries, or 22.5v ones, for that matter for flash applications, is the internal resistance of the battery itself. These are true batteries (ie, a stack of 1.5 volt cells), and have higher internal resistance than a single cell. 3 9v batteries in series will provide 27v open circuit, but since the internal resistance of the batteries is added together in series, you will gain voltage, but not current.
I did a quick experiment, and found that an alkaline 9v battery on my desk will deliver a short-circuit current of 1.5 amps, max. This means the internal resistance of the battery is about 6 ohms. So if you stack two 9Vs, you get 18 volts, but the internal resistance of the stack is now 12ohms, and you'll still get only 1.5 amps, assuming the bulb is 0 ohms. As someone pointed out, a single alkaline 9v can reliably flash a bulb- using a higher voltage won't give you more (or less) current without a capacitor. Add a cap, however, and your current will be determined by the energy stored in the cap, rather than the resistance of the battery. That's why it's useful to use a lightweight, low-current battery, and a good cap, rather than a big heavy high-current battery.
Oh, and single malt scotch will improve the performance by at least an amp or so, two amps for an Islay.
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C. Henry



Joined: 13 Dec 2005
Posts: 359
Location: North East Georgia, USA

PostPosted: Wed Mar 05, 2008 8:27 pm    Post subject: Reply with quote

Similar tests on a single carbon/zinc "C" cell (good but not totally fresh) gives a dead short current of 2.25 amps for an internal resistance of 0.66~ ohm, an alkaline "D" cell (also good but not totally fresh) read 3 amps for an internal resistance of 0.5 ohms.
If I recall correctly the old carbon/zinc cells (which were all we had in the 1950s) had a lower internal resistance than the modern alkaline cells but became exhausted with a lot less total use than the alkaline cells. I was surprised that the "D" cell that I tested did not have that much more dead short current than the "C" cell, probably supporting my recollection of the difference between the two types of cell.

C. Henry
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robcruickshank



Joined: 25 Feb 2008
Posts: 19
Location: toronto, canada

PostPosted: Wed Mar 05, 2008 9:27 pm    Post subject: Reply with quote

Apparently there were special zinc-carbon batteries just for flashes:
http://en.wikipedia.org/wiki/Photoflash_Battery
I've seen these referred to in old manuals, but i guess I'm too young to have ever seen one, although I remember my dad's flash with a 22.5V battery.
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Henry



Joined: 09 May 2001
Posts: 1442
Location: Allentown, Pennsylvania

PostPosted: Wed Mar 05, 2008 9:51 pm    Post subject: Reply with quote

I'm concluding from this discussion, incl. the Wiki article, that fresh alkaline D cells will work just fine in my 2-cell Graflite. What say?
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robcruickshank



Joined: 25 Feb 2008
Posts: 19
Location: toronto, canada

PostPosted: Wed Mar 05, 2008 10:06 pm    Post subject: Reply with quote

Henry wrote:
I'm concluding from this discussion, incl. the Wiki article, that fresh alkaline D cells will work just fine in my 2-cell Graflite. What say?

Should be just fine. I often use plain old carbon-zinc batteries with no trouble, although I'm typically only shooting maybe 6 bulbs in a session.
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C. Henry



Joined: 13 Dec 2005
Posts: 359
Location: North East Georgia, USA

PostPosted: Wed Mar 05, 2008 10:28 pm    Post subject: Reply with quote

Fresh alkaline "D" cells should be OK, carbon/zinc "D" cells might be better for photoflash use (Rayovac Heavy Duty is one brand) and are cheaper to buy but will not last as long.

C. Henry
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