Multiblitz IIIb

[iconoclastica]

This week I was offered an apparently rather old flash unit with few markings. I could get it for free, but I only accepted it reluctantly since it is a bulky and heavy apparatus. Now I am googling the thing, I am starting to think it may be more interesting than I thought.

This is how it looks like (top-part of controller shown only):


The controller screws apart into two separate units, the bottom one I think contains the battery and the top one is powered by the mains.

According to this one advertised on ebay it should be capable of emitting 10ns flashes.

It didn't come with the original power cable and the power connector is not one I recognise, so I can't test it right now. It may be possible to change that connector, although looking through the ventilation slits, it does seem somewhat integrated inside..

Apparently there is a manual abroad on the internet, I see one on Pinterest, but I yet have to see one that can be downloaded.

[apt403]

Nice score! 10ns certainly sounds interesting for freezing motion!

If you upload some shots of the back of the unit, maybe we could help identify the cord type. Wiring a new, more common plug should be reasonably simple as well.

[enricosavazzi]

According to the eBay ad, 1/100,000 s. This would make it 10 microseconds, not nanoseconds. Still much shorter than an ordinary electronic flash at full power, but only 100 times shorter.

[iconoclastica]

@#$%^!! I am going to avoid using those prefixes. I keep using them wrong...

[iconoclastica]

Nice score! 10ns certainly sounds interesting for freezing motion!

If you upload some shots of the back of the unit, maybe we could help identify the cord type. Wiring a new, more common plug should be reasonably simple as well.

The socket reminds me of the ones seen on old clothing irons from the 1950's. It has two flat connector pins and I hold it the case connects to the mass (or gound). Diagrammatically it looks like a C10 connector but I haven't seen the detail specs yet. Moreover, this German wiki states that it is not grounded.



It was fixed by two screws through a bakelite plate and I though it an easy job to get it out. But it turned out they are bolts with the nuts inside, so I couldn't get it back in. Nothing to it than to open the unit:





It appeared one of the pins had got disconnected. Perhaps it was like that, or I did it this morning. Having come so far, I think it best to replace the connector with a modern c14, so a wide range of cords become available.

Still desparate for a manual. It does exist.

[dickb]

This week I was offered an apparently rather old flash unit with few markings. I could get it for free, but I only accepted it reluctantly since it is a bulky and heavy apparatus.

This looks very familiar.. I for one am glad you took it, otherwise I would have had to lug it back again. Jan got it from the sale when the university discontinued its own photo lab. I already have a collection of Metz 60CT s, partly from the same sale. Good to see you getting to grips with it, your electronics skills are bound to be better than mine.

Groeten,

Dick

[iconoclastica]

What a surprise to meet you here, Dick!

Wim

[enricosavazzi]

The capacitor is massive. Some of the lettering on the capacitor may be hidden in the picture by reflections on the metal, but I seem to read 40 μF and perhaps 5 kV (very doubtful about the latter). If so, this is an unusually low capacitance and an unusually high voltage for an electronic flash. It might in turn mean that the xenon tube is unusually long (perhaps coiled many turns?). It also means that the high voltage in this unit is particularly, dangerously high. More so than in modern electronic flash units, which typically do not exceed 300-500 V.

You will need to be very careful not to electrocute yourself by touching something in this unit, even when powered off and even after firing the unit to discharge the capacitor. Also very careful to keep water away from the unit.

--AdminCS edited micron symbol

[dickb]

What a surprise to meet you here, Dick!

Wim

Indeed, although your location tag had warned me that I wasn't the only Wageninger here.

It might in turn mean that the xenon tube is unusually long (perhaps coiled many turns?.

It is, on first glance I thought it was a continuous light. The tube has at least six turns / coils.

[iconoclastica]

It is 40 muF indeed. I think the voltage is 2.5kV - I have just screwed the aluminium lid back so I can't check it now. On the non-reduced photo there seems to be a comma in front of the 5.
Yes, these values scare me. I once shorted a modern studio flash with a chrome-vanadium screwdriver, just before touching the same with my hand. I still hear the bang and see the smoking hole in the metal... The power socket is just about as much as I dare to handle. I am not even sure if I have the courage to connect the battery.

Yet it seems to me that someone has already tampered with it. Around the power socket is a backdoor that can easily be opened, as I know now. It appears that there are two measuring probes where the texts suggest there ought to be control lights. This is one of the reasons I very much would like to see the manual.

[iconoclastica]

I did some searching on the Bosch MP capacitors. The 40muF/2500V was not an uncommon type n the 60'ies and 70'ies. But it is an electrolytic capacitor.

Is it still wise to try to power it on?

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EDIT: It is not. The cap is maked 2/64, so it's exactly as old as I am. It has not been in regular use for over 20 years. I expect a big bang.

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EDIT2: The marking MP means metallo-paper, so a paper film/oil capacitor - not an electrolytic one

[dickb]

Is it still wise to try to power it on?
----
EDIT: It is not. The cap is maked 2/64, so it's exactly as old as I am. It has not been in regular use for over 20 years. I expect a big bang.

Things have started with the big bang, ending it that way doesn't sound too great. At least you didn't overpay. Perhaps someone sees a value in it as a decorative item?

[iconoclastica]

It's not the end of the story yet. It might be possible to reform the capacitors (yes, plural, for there isn't any battery at all, but a second nearly identical capacitor in the bottom unit). Only I think I wil build a trickle charger for that purpose that can power the unit on with shorter pulses and much more patience than I could do it by hand.

Don't expect me to have it running next week ;-)

[iconoclastica]

Once I got convinced the caps are not the explodig kind, and having measured the resistance non-zero, I gathered courage to power the unit. I hid from direct view nonetheless, but the unit behaved gentlemenlike. There's a test/release button on the head and when pressed, the head emits a bucket of light with a loud popping sound.

I haven't figured out yet the use of the bottom part with the second capacitor: more light? faster reload? extra ballast?

Compared with a speedlight, the light intensity roughly equates GN 72.

How could I estimate the duration of the flash?

[mawyatt]

Felix,

Good work!!

An easy way to "see" the optical burst is to make a simple optical detector.

Any silicon diode will work if not sealed from light, the 1N914 or 1N4148 will work, also an LED will work.

Shunt the diode with anything from 50~100K ohms and connect to an oscilloscope with waveform storage, reverse the leads if the waveform is upside down.

Place the diode in the optical path and trigger the scope from the channel the diode is connected to. Use Single Sweep positive edge trigger (~200mv), set the Vertical Scale to ~500mv/div and Horizontal Scale to 10us/div since this is a fast strobe. Adjust accordingly.

You should get a waveform that looks something like this.



Best,