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Busch B-C Flashing Unit help-

 
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JohnRichard



Joined: 22 Aug 2009
Posts: 6
Location: Lexington, KY

PostPosted: Fri Sep 04, 2009 1:42 pm    Post subject: Busch B-C Flashing Unit help- Reply with quote

Greetings!

So, now I know more than I did, but that still doesn't help me.




Ok, so as you can see, those that have told me to use "D" cell batteries; they will not fit. That metal post is in the way. Besides, I believe I could only fit one battery in there anyhow, and I don't think 1.5v is enough to set off a #25.

Someone suggested an Eveready 412, 22.5v. This will not work either, because the physical dimensions of that battery are almost identical to that of the standard 9v. I do want to use this flash. If we can't come up with something, then I am going to have to buy a new flash, which I don't want to do.

My current line of thought is to build a battery pack consisting of 4 "AA" batteries, hardwired into the unit. 4 "AA"'s is just about all that will fit in the base of the unit, and have the cap be able to screw on. So, those kind souls that are racking their brains trying to help me make this work, keep that in mind.

Thoughts?

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JohnRichard



Joined: 22 Aug 2009
Posts: 6
Location: Lexington, KY

PostPosted: Fri Sep 04, 2009 4:28 pm    Post subject: Reply with quote

Ok, That didn't work. I still can't believe that is takes 22.5 volts to fire a flash that I can fire hard wired to a 9v.
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C. Henry



Joined: 13 Dec 2005
Posts: 360
Location: North East Georgia, USA

PostPosted: Sat Sep 05, 2009 11:32 am    Post subject: Reply with quote

John;

The critical factor is the current through the primer of the flashbulb.
According to the Photo Lab Index the voltage range for a #25 flashbulb is 3-45. Some big bulbs (like a #50) have ratings up to 3-125!
Your unit is called a "B-C" unit which means that the battery charges a "condenser" or "capacitor" then the charge in that is dumped through the flashbulb to fire it. This was done so that a low current battery could fire a flashbulb on time rather than late as would happen with limited current from a small, weak or stale battery.
While three volts will fire a #25 flashbulb if enough current is available, more voltage up to the high limit of the bulbs rating will add reliability to the timing of the bulb.
A "B-C" unit will always fire a bulb "on time" if it fires it at all, while a straight battery flash unit may fire the bulb late if the current supplied to the bulb is low.

C. Henry
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C. Henry



Joined: 13 Dec 2005
Posts: 360
Location: North East Georgia, USA

PostPosted: Sat Sep 05, 2009 11:44 am    Post subject: Reply with quote

John;

Other possibilities for the battery on your unit are 15V #220 and #504, both of which are smaller than a #412
Watch the polarity as many of the capacitors used in "B-C" units are very polarity sensitive and can be destroyed by reverse polarity!

C. Henry
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Les



Joined: 09 May 2001
Posts: 2682
Location: Detroit, MI

PostPosted: Sat Sep 05, 2009 12:17 pm    Post subject: Reply with quote

Another concern is the existence of the condenser. Back when BC flash units were common, condensers / capacitors were made much like batteries that used spring contacts rather than something soldered in.

If the battery went in on top of the spring in the photo, it's possible the capacitor occupied the other side and is now missing. Is the bright spot deep inside the flash unit a contact? Is there anyplace else in the unit where they could have put the condenser?

If not, you've got another hurdle to jump--finding a capacitor to fit. Electronic Specifications for the capacitor aren't critical. Something around 270uf @ any voltage above 22v will work. (Condensers work with the battery voltage, so a condenser that's rated at 460v being fed by a 15v battery will be 15v)
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JohnRichard



Joined: 22 Aug 2009
Posts: 6
Location: Lexington, KY

PostPosted: Sun Sep 06, 2009 10:23 pm    Post subject: Reply with quote

Well, I decided to get a 3 cell flashgun, rather than trying to figure out how to fix this one. I need a fully working camera with flash bulbs for a shoot at the end of the month. I think I got a really good deal on the gun, as I can load it up with "D" cells, and it comes with a PC cord as well as a bipost cord so I can use it with my 135 equipment too.


As for your questions: I also believe that the thing on the other side of the battery spring is a contact for the capacitor. Sadly, I do not have it. Every time I purchase something, it saddens me a bit more when I have to 'find' parts to make it work.


Maybe someday I will figure out something to make this work, but for now, I'm just going to use my new 3 cell unit.
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