View Full Version : Old Braun Hobby EF-300 Flash rehab

Mike Wilde
12-13-2007, 11:01 AM
I like taking photos with older gear, and getting great photos with it. If I can bring the gear back from the dead, so much the better.

I guess it is a revenge move against the other types of photo that any monkey can make with a digital camera.

Lighting indoor portrait scenes with flash bulbs is nice, but I try to save them for special events, because... they just are not being made in the sizes I use any more.

Shoe mounted electronic flash units have their limitations when I shoot medium format and want some depth of field for a group portrait- not enough umpf. I do have a Metz 60CT1 that I use often, but a second unit giving a similar whomp of light would be nice to use as a fill or main.

I was given a derelict Braun Hobby EF-300 pack and handle mount head rig last month from an older member of a camera club whose meetings I sporadically attend.

He had emigrated to Canada in 1969, and the flash rig and his old 35mm camera were all the photo gear that he moved here with; he had sold up all of his other gear back in Ireland before departing. This flash sat unused in his basement for many years because he could no longer find replacements for the wet cell batteries that ran it.

I took the unit home for a work over.

Once down in my work shop, and out of its carry case, the rubber insulated coiled power cord that linked the power pack to the flash head crumbled as soon as it was extended.

It has been replaced with about 15' of 'toaster type' flexible heater wire - a 16 gauge twin conductor cable with a heavy tough rubber jacket. It was the only wire that I had on hand that was suitable for not having its
insulation break down under the dielectric strain that the 500V DC output that the power pack can generate. The power cable was made up to be long enough to allow the head to reach out onto a boom stand, is otherwise neatly coiled up and held in place with a Velcro tie located near the plug for the power pack. Just enough wire is left uncoiled to allow the flash head to be held up at the end of my out-stretched arm, with the battery pack hanging off my shoulder.

An internal examination of the power pack revealed no sign of any oozing capacitors, etc, and showed a manufacture date of 10 Okt 67.

The OEM style wet cell batteries indeed are no longer attainable. I ran extension wires from the old battery connecting terminals and hooked them to a 6V source. There was a convenient hole in the case from where a cracked battery in the past had leaked acid that ate a nice hole in the side of the battery housing. The wire went out that hole.

The source for the initial bench test power was a 6V AGM type battery of the sort that would usually power a small UPS, and which for me which also does backup studio shoot duty with my Metz 60CT1 pack when its normal dryfit goes flat and is being charged.

I turned the Braun unit on with the test battery connected, and the old pack began to whine as the oscillator powered up for the first time in likely 35 years. I left it charging for half an hour to allow the electrolytic capacitors in it to re-form.

After leaving the unit to charge for a while, the flash tube fired without a problem when the test button was depressed. It is still a powerful unit. The calculator dial indicates it has a guide number of 160 at full power, and 80 at half power (ISO100, rating in feet).

A test with my flash meter shows that light output is still up to those levels, There is no thyristor controls on this unit. It dumps the whole charge. Half power cuts the voltage that the capacitors fire up to to about 340V. With the 6V cell powering the unit the recycle time from a full dump was about 20 seconds, a bit slower than I was initially hoping for.

The AC power cord was plugged into the unit, and it's charger functionality was verified. The charger circuit does constant current charging at approximately a C/10 current rate for a 5 Ah battery. The AC power will also charge the capacitors in the power pack, albeit very slowly.

The down side at this stage was that the charging voltage being impressed on the battery suggested that the power pack wanted to be fed more than 6V in battery voltage.

Originally the unit had two wet lead acid cells, and it looked like they had each been two cell units, that together delivered 8V. I guess 40 years ago there were not the plethora of battery powered devices like today, so using a non standard battery voltage was no big deal. Or alternately maybe they wanted to capture all future battery replacements by making them an item that you could only buy from the OEM.

I wanted to go with a sealed lead battery, since they keep their charge for a long time. NiMH batteries are good if you charge and use them regularly, but that is not how my photo flash gear usually gets used.

A web search turned up 2V AGM sealed lead acid cells, marketed under the trade name Cyclone. They looked good, so I ordered 4 of the 2V 5Ah units online, for about $100Can including shipping. So far this was the only money that I had put into this rehab, and if it worked, perhaps the bug to buy a used studio flash rig will be quenched for a while longer.

After about 6 days, inlcluding a weekend, my batteries arrived!. I made up a wiring harness after work the day they came, and left the new batteries to float charge over dinner and the time spent getting the kids to bed. When I came back to the workshop, all was ready. Testing with these batteries show that at full power recycle time is about 5 seconds. We were in business.

I made up a new case to carry the 4 new cells under the original power pack, since the form factor of the new cells precludes fitting them into the original battery compartment. The case was made from the ever versatile combination of 1/4" foam core board and clear packing tape. There is no end to the uses that I put foam core to. I took care to make sure that the wiring harness cannot short any of the terminals. These batteries, that are called x-cells - they have two push on terminals on the top, and are kind of like oversized D-cells on steroids. If shorted, they can deliver 65 amps!. No wonder the flash recycles fast with these things. Right after the tube fires the oscillator circuit draws about 6 amps from the batteries.

I have used the flash once at the camera club to show off its rehabbed state. We were doing a macro workshop, and it was certainly nice to be able to bounce this off a foam core reflector, and allow the lens to be stopped down to f22 to improve on the always limited depth of field when macro is the genre.

Last night was the first time I put the now functional flash to good use for the distance of flash it allows. I hooked the bracket for the head onto the bottom of my trust old Minolta SRT-101, and hooked on a 70-210 F4 lens for taking pictures of my youngest son's first Christmas recital at school. The power of the flash allowed me to shoot effectively with 400ASA film at f5.6 for the 50 feet or so from the stage that I was shooting. It is now ready to do duty this weekend at a shoot I am doing for front of house photos for a community theatre group play. These always seem to bring in more head shot and portrait work, so the $100 spent on the thing might be recovered soon.

03-06-2008, 11:36 PM
Nice job, I'm in the process of rejuvenating an even older Braun Hobby EF3. The 2 cell 4 volt lead acid batteries were standard units way back then, although in 67 that would have been towards the end of common usage as nicads and lead acid packs were available for the Braun F 800.

They were high power units but when high speed slide film was ASA 25, you needed it. :)


05-27-2009, 04:08 AM

I have been thinking of repairing my fathers old Braun Hobby flash. So far I havent found the model, but it had a 4V Sonnenschein battery in it.

Was the battery charged simply by plugging a cord to the power pack or was there a charger? Is it possible to run the flash directly from AC-cord with out a battery?

05-27-2009, 07:40 AM
I used to own a Braun Hobby flash, with wet cells as you describe. It was indeed a very powerful flash; I often used it to take yearbook pictures of high school basketball games in the late 1960's. One interesting design aspect is that the flash tube is offset somewhat within the covering glass envelope. This allows you to turn the reflector one way or the other around the tube, thereby changing the nodal point of the flash vis a vis the reflector, thereby throwing either a wide-angle or more narrow-beam flash. And you could pull the reflector entirely and go bare bulb -- which makes for very interesting photos when used in a room, so you get reflected light from all directions.

05-27-2009, 09:57 AM
SMN, yes to both your questions.

05-27-2009, 10:09 AM
I have an Ascorlight 1600 that the battery pack was no longer avalible for and after looking for years I found and purchased the 1/2 D cell rechargeable cells to make a new battery pack. it worked fine But now the battery holder cap has fallen apart and my atempts to repair it have failed. Wish I could find a suitable replacement! This was every bit the equal to the Metz back in the day when I purchased it well actually traded a Rollie E36 RE unit and some cash for it. The Rollies had a under rated transistor that burned out and was pretty much impossible to get. Unfortunately like many things Berkley marketed they did not stick with the very fine Ascorlight very long.

Mike Wilde
05-27-2009, 12:01 PM
consider self amalgamating ruber tape. Also fimo modelling clay, and hot melt glue to reinforce it where required. or coated to waterproof it. With foam core thown in, I can bring almost camera gear that has physically broken down back to life. It may not look as pretty as when it was new, but that is a lot like me at middle age too.

05-27-2009, 02:25 PM
Thanks for the ansver Mike.

I thought it would work this way. I have heard a few rumors concerning condensators this old burning and wanted to be sure before trying.

Nick Con
05-09-2011, 06:37 AM
I know this thread hasn't been touched for a while, but it is the first thing that Google throws up when you search for the Braun Hobby 300 - so this seems a good place to post additional info about the thing.

Anyway. I refurbed one of these units about 8 or so years ago now. Mine was fitted with the original lead-acid "dryfit" cells when it came into my possession. Needless to say, the cells were all shot and rotten. Mine had a completely solid battery door, but I believe there was an earlier version which took wet lead-acid cells and the battery door had slots in it through which could be seen some coloured float balls indicating the state of charge of the batteries. Phew! Sorry about that over long sentence.

So, cell technology has moved on, and I didn't see any reason to stick with the old lead-acid technology. I found that 6 C size Nicad cells would easily fit into the space left by the original batteries. I wired two sets of 3 tag-ended C sized NiCads in series and attached the original wired plugs from the old batteries. I was a bit fearless and didn't do any pre-testing; just turned the old thing on. A reassuring whine followed and eventually the neon indicator came on. The test button was pressed and an impressive burst of light shone forth.

To cut a long story short the NiCd cells worked a treat and the unit behaved as if there was no difference in voltage - even though the NiCds theoretically feed it a slight undervoltage. The built in charging worked as it should as well. The 2 sets of 3 C cells were taped together to make a jam fit into the battery compartment and the cover held them in place nicely. No hole or taped-on box needed! (with apologies to Mike, the OP)

As I say, this was 8 or 9 years ago, and a recent investigation has revealed that the NiCd cells have all grown nice furry beards in the meantime. I think I'll try Nickel Metal Hydride cells this time around. They're cheaply obtainable in the common C size with a capacity of 4 Ah or more. If all goes well I'll post back.

BTW, thanks to the OP for pointing out that the voltage of the unit is 500v. I was going to use it to power an old 6 inch diameter "Minicam" brand flash head, but I think the head was designed for only around 350 volts or so. It might be time to get fearless again!

Mike Wilde
05-09-2011, 10:32 AM
I have since made a few other changes. I had the local emergency exit lighting maintenance contractor come around the office servicing their DC power packs. A few had packs with a battery string that had failed. I asked for the dead battery packs, with the deal that I would pay him the scrap lead value of any I kept. Well, I don't need 24V, and found that in most the failure was down to infant failure of a single battery in the string. So I brought my battery conditioner/charger in and charged up pairs in 12V configurations to see which were still healthy, and which were sulphated, etc.

I ended up with four functional 6v 10Ah batteries all less than 2 years old, that were very lightly used, for $5, and gave the other weaker unti back to the contractor the next day.

I now have the Braun running on 2- 6V10Ah, and 2- 2V 8Ah cells to give heaps of capacity before the need to charge them. I usually stand mount the head firing it into a 24x36 soft box, and hang the accumulator and batteries pack half way up the light stand to stabilize the whole affair. It makes a great light for shooting portraits on location at a theatre during rehersals for head shots of performers. Print of these photos end up being posted on the front of house display board, and scans feed to the program bios area.