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Kraken de Mabini

A Tour Inside the Sea&Sea Yellow Sub 50 and 60 Strobes

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Tour Inside the Sea&Sea Yellow Sub 50 and 60 Strobes. 


The YS-50 and 60 underwater strobes were designed for the Nikonos V film camera, with flash control via sync cord. The strobe case and electronics are simple, the only strobe control is a switch for Off and TTL. 

The Sea&Sea YS-50 underwater strobe has accessible electronics that implement an early version of TTL.

The case and boards are accessible and repairable if parts are available.

An understanding of this early strobe may help in dealing with the problems of the newer YS-D... series of Sea&Sea and similar strobes.-

A number of Wetpixel members have posted their underwater strobe problems and some ask how to open and how to repair a strobe (refs). Most of the posts seem to refer to Sea&Sea strobes, maybe because of their popularity. Some of the concerns with strobe performance and quality are discussed in 'Our Strobe Problem' (1). 

Information to develop a practical approach to these problems includes a description of a strobe's insides. For this, Sea&Sea strobes are convenient as they are built in a logical manner and can be opened easily, plus early Sea&Sea strobes such as the Yellow Sub 50 are simple and understandable. I start with the anatomy of this simple strobe, and hope to expand the discussion in a later post, in an effort to first understand and then begin to deal with the following issues: 

.UW strobes fail, often from minor defects,

.No official circuit schematics or repair manuals are available,

.Dealers rarely want to or can repair them (In ref 3 I list many of the world’s repair sites, but from what I have heard and seen,  I suspect most do not accept burned out or non working strobes), and

.Some of us want to repair them but have no source of information or parts. 

Strobe Case

The Sea&Sea Yellow Sub 50 case is a cylinder with front and back halves that plug into each other, held together by three 1 mm cross-head Phillips screws. A 3 X 74 mm Buna-N O-ring waterproofs the joint (same case construction and O ring size are used in the YS-110, -D1 and -D2 strobes) The halves are designed to be easily separated and reunited.  

The transparent front half has a clear front lens.  Its under side is a molded slot for the YS or ball mount, with a matching slot in the rear half to hold a rectangular metal plate to which the strobe mount is screwed. There is no spot light, photo diode trigger or fiber optic connector. 

The rear of the strobe case has the plug-in contact for the sync cord, with its screw-on cap. On its back is the rotary Power Switch for the Off, On and TTL settings, an indicator light and the battery compartment opening and cover. The Power Switch protrudes inside the main compartment, and is retained by a circlip; it has a cam to actuate the two on-off push button switches on the electronic board. 

TTL Sunc Cord:

Strobe TTL is controlled by a Nikonos V camera via a sync cord with four wires: red, white, green and yellow,  connected internally to a socket in the electronic board. 

The Battery Compartment is molded into the rear case.    


 Fig. 1. A thin printed plastic ring with 'Open, Lock, On, TTL' printed on it, is glued around the battery compartment opening. Under this label, eight small screws secure a plastic ring with three square tabs that lock closed the battery cover.   

The battery compartment has no battery dividers, no water sensor. At the bottom is a spring metal strip that connects in series two of the batteries, and two round head bolts with a hexagonal neck which pass through the compartment's bottom, each sealed by an O-ring and retained by washers and hex nuts, to  connect the four AA batteries via a red and black wire to the internal electronics. 

The battery cap is simpler than the current cap for the YS-110, -D1 and -D2 strobes, has 4 coil springs instead of the newer leaf springs to connect the four batteries in series, and no high pressure gas release vent. 

The Main Compartment has the flash tube, capacitor and electronics. (It is a good idea to remove the batteries and discharge the photo capacitor when opening and examining a strobe's electronics). 
 The electronic board assembly is L-shaped, with a semicircular horizontal board (63 mm diam), connected edge to edge to a flat square board (63 x 95 mm). The horizontal board has the xenon flash tube and reflector, while the vertical board carries the electronic circuits to flash the xenon tube. 
 The flash tube is U shaped and held within a tea cup shaped, circular paraboloid reflector; + and - wires are attached to each end and the bare copper trigger wire is connected to its middle.                           


 Fig 2. Circuit board of the YS-50 showing the clear labeling of the solid state components, the H5G2E1 thyristor is upper right, the two push button switches are the black boxes near the bottom center. The main capacitor is on the under side of this board. The nut and bolt construction allows one to open and reassemble the strobe with ease.

 On one surface of the vertical board is mounted a large photo flash capacitor, CE62P of 1100 uF and 330 V, the electronic components are mounted on its other surface. This design allows the observer to draw a diagram of the circuit (Fig 2). For the YS-50 and YS-60 strobes the circuit diagrams were published by D W Knight and Laszlo Kalmar in the Russian log 'Impulsite - Pulsed Light in Photography' (4).



Fig 3.  Sea&Sea Yellow Sub 50 TTL-II electronic diagram, by Knight and Kalmar (4)

_ _ _ 


Fig. 4.  Sea&Sea Yellow Sub 60 electronic diagram, by Laszlo Kalmar (4)

 Although no microcomputer is present, this and similar S&S strobes with TTL have a basic electronic circuit, based on the H5G2E1and similar thyristors (now obsolete) with timer capability, to process the TTL signal provided by the camera and translate it into a useful strobe flash.

 The camera's TTL pulses are sent via the sync cord to the strobe's electronics and H5G2E1 thyristor to control the flash's duration. 


 A notable feature of Sea&Sea strobes such as the Yellow Sub 50 and 60 is that early in the evolution of underwater strobes, their designers incorporated TTL flash handling electronics based on an insulated gate bipolar thyristor (IGBT) to translate the exposure information from the camera into an appropriate light pulse, a precursor to the microcomputer of later S&S strobes such as the YS-110.
 Another feature of these early S&S strobes is that their modules are built to be easily accessed and replaced. 
 An understanding of these early strobes may help us begin to deal with the problems of the newer Sea&Sea and other makes of strobes.  

- - -


1. Legend has it that brothers Masaoki and Masateru Yamaguchi of Sea&Sea designed the first mass produced underwater strobe in 1972 and named it "Yellow Sub" in honor of the classic Beatles song.

2. Our Strobe Problem. https://wetpixel.com/forums/index.php?/topic/63956-our-strobe-problem/&tab=comments#comment-405732

3. World List of UW Camera Housing and Strobe Repair Sites. https://wetpixel.com/forums/index.php?/topic/64815-world-list-of-uw-camera-housing-and-strobe-repair-sites/  

4. Knight, D.W. and Kalmar, L : Sea&Sea YS-60 and YS-50TTLII circuit diagrams.  https://impulsite.ru/viewtopic.php?t=1249

Edited by Kraken de Mabini

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Rather than say it's good idea to discharge the capacitor - I would say it is essential.  A 50 W-sec flash with that energy stored at 330V could fatal in the right circumstances.  Don't fiddle unless you know what you are doing.  Shorting such a capacitor could vapourise the wire used to short it and even cause the capacitor to explode.  You also need to be sure the capacitor does not build charge again once discharged normally.

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I have an opened up S&S YS-D2 strobe if you want photos of that as well. The non-J model.

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