Braun F 245 LSR flashgun: Dissection

[Andreas Thaler]

A Braun F 245 LSR flashgun, behind whose flash reflector glass there was a suspicious trickle. That’s what corrosion sounds like!

I didn't find a battery compartment, but I did find some screws.

I wanted to see how the device is constructed and what electronic components can be found.

From the way the device presented itself, the flash capacitor must have been discharged long ago, but I still approached it carefully.

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Before you open an electronic flash, please consider this:

• You should only open flash units or cameras with inbuilt flash if you know exactly what you are doing. The main capacitor of even small electronic flashes can charge to a dangerous voltage.
• High voltage is dangerous!

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The cover, all internal parts are already removed.

The main electrolytic capacitor, which I checked for voltage immediately after opening the housing.


There is 13 mV voltage between anode and cathode.

This is far away from the operating voltage of 300 V or higher and is harmless.

Nevertheless, I only touched the circuit board with my combination pliers, which were insulated to 1000 volts.

Because I didn't know whether I could rely on my voltage measurement. Since there was corrosion, the measurement could show low voltage due to oxide layers on the connections.

In any case, a good exercise in the safe handling of high-voltage devices

Using the insulated pliers I cut the cables from the electrolytic capacitor to the circuit board.

I want to keep the fat guy at a distance

There are obviously two leaking batteries on the bottom of the circuit board.

Here I measured an equally safe 44.5 mV.


However, it is not clear to me how the two batteries are connected to the circuit board.

So it's better to stay away. Although I don't suspect any dangerous voltage here.

Overview

Details

You can see, among other things. analog electronics with capacitors, resistors, glow lamps, trim potentiometers, coils and a beautifully, I suspect, hand-soldered circuit board.

Everything is in a rotten condition caused by leaked battery acid.

So thanks for the insights and off to the sack for the electrical bulkhead.

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Conclusion

• Corrosion caused by leaked battery acid and electrolyte is the number 1 enemy of photographic device electronics.
• Even if the devices look good on the outside, things can be different on the inside.
• For devices that you want to keep for years to come, a check is recommended.
• The electronic components alone are interesting. But it is their interaction as a circuit that gives the device function. It would therefore make sense to show the circuit diagram here, unfortunately I don't have it.
• To put it simply, voltage from batteries is transformed into high voltage in the flash unit. This high voltage is then discharged through a glass tube filled with inert gas, creating a light pulse known as lightning.

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All information provided without guarantee and use at your own risk.

 

[Kodachromeguy]

Interesting, 1960s discrete components electronics.

Many (most) Leica MR-4 CDS light meters were similarly ruined by leaking batteries. Repairing these MR-4s might be a lucrative business venture. They were quite handy because they coupled with the speed dial.

 

[Andreas Thaler]

Interesting, 1960s discrete components electronics.

Many (most) Leica MR-4 CDS light meters were similarly ruined by leaking batteries. Repairing these MR-4s might be a lucrative business venture. They were quite handy because they coupled with the speed dial.

This is all manual work in assembly.

Unimaginable today.