More Home Camera Repair

Posted 2009.10.16 16.55 in Hobbies, Photography by Stephanie

The codeine buzz didn’t last long, so in an attempt to draw my attention away from the unbearable seething agony in my mouth, I decided to have a go at repairing another camera.

Hanimex RangefinderToday’s victim subject was my Hanimex Rangefinder. I’ve looked high and low on teh interwebz but have yet to find any more information on this camera. I’m confident that it works like the Hanimex zone focus ZF35, and is almost certainly made by whomever made the ZF35. I have parts of the ZF35 manual, and between that information and what I’d ascertained when I originally disassembled part of the Hanimex, I am confident that a) my RF35 is functionally equivalent, b) the mechanical shutter operates at full speed when there is no battery power, and c) the metering system (when it works) uses an electromagnet to delay the shutter closing.

In other words, the shutter is cocked and released in a fully mechanical fashion. However, there is a small electromagnet (basically a small relay coil) next to an armature which, when released, closes the shutter. This armature has a small steel weight attached. Without any power whatsoever, the armature moves unimpeded and its maximum speed is probably 1/300th of a second. When the small coil is powered, this magnetically holds the armature in place until the current is removed. This delay is what allows the camera to employ slower shutter speeds.

There is no computer chip in the camera; the amount of time the coil is energized is determined via fairly straightforward discrete electronics. The ‘electric eye’ CdS is a light-sensitive varistor. Film speed and aperture settings are ‘programmed’ by moving small shutters with varying degrees of transparancy. For instance, at ISO 100, only 1/4 the light gets through as does at ISO 400. The same thing with apertures. So the light that reaches the CdS is mechanically filtered based on film speed and aperture.

The amount of resistance in the CdS then controls a capacitor which in turn controls the duration the shutter delay coil is energized. The camera also has a ‘test’ button which will light up one or two small lamps by the viewfinder – when the ‘test’ button is pressed, this simply measures the power through the CdS against a fixed value (possibly a pair of Zener diodes) and if there isn’t enough light then one indicator is active, and if there is too much light then the other indicator lights up. If neither lamp is active, then it’s safe to take a picture. (Or the battery is dead!)

So, enough background already! The part of my Hanimex that was broken was that all the electronics seemed dead – brand-new battery, yet the indicators would not light and the shutter would not change speed. I suspected that it was simply a broken wire from the battery compartment. However, getting inside the camera was quite tough – no manuals, no way to know how to approach it… like one of those puzzle boxes, where if you undo the wrong thing or something in the wrong order it breaks.

Exactly like that, in fact.

SurgeryI tried a number of approaches, including removing the lens section (one piece at a time…) but eventually I discovered that the problem was some screws were hidden under plastic that I didn’t realize was just glued in place. So I put together everything I had torn apart, and just focused on the area I needed – the top plate. This meant removing the winding lever, removing the rewind knob, and removing some glued-down plastic, then finally getting the top plate free.

Yes, I did undo one screw I shouldn’t have. You know you’ve made a mistake when you remove a screw and a) what you expect to happen, doesn’t happen, and b) something inside that you haven’t got to yet, goes “pop, click, rattle.”

Anyhow, with the top plate finally off, I was able to inspect the battery connections. At first glance they looked fine. I decided to find and fix the pop/click/rattle. This turned out to be a special two-ended nut that a) put spring tension on the winding lever so the lever returned to normal position after cranking, and b) held in place a spring that tensioned the counter reset, so when the back was opened the counter reset / when the back was closed, the counter functioned.

It only took me three tries to figure out how to put that back together. Not bad, I think, considering I’d never seen what it looked like intact. That done, it was back to the main problem.

Sometimes, I have to come right out and say that something is poorly engineered. Not often, and having no real engineering training myself, it is perhaps a bit presumptuous. Nonetheless, there are times when something is just plain wrong. This is one of them.

The main connection for the positive battery, was a solder joint between a brass strip, and some chrome-plated metal. This solder joint had failed. Why? Well it’s very, very hard to solder to chrome plated anything! And if the metal underneath the chrome is steel, nickle, or some alloy thereof, forget it. Further complicating things, the camera’s top-plate is made of plastic. This means if you get it hot enough to get a good solder joint, odds are the metal bits are just going to fall out as the plastic fails.

Fault

I’m no world-class expert solderer but I know what I’m doing. I managed to repair the joint with a minimum of plastic disruption. I added a bit of copper wire to provide extra strength and support, and it seems to have done the trick. Once the camera was reassembled, I tested it and everything seems to be functioning now – the exposure indicators, the shutter speed. Slowest speed seems to be about 1 second.

Damage to the camera itself has been minimal – I lost a little ball bearing that makes the film speed setting go ‘click click click’ (I just hope I didn’t drop it inside the camera.) And part of the decorative trim was buggered up and won’t go back on. Ah well. I’m pretty sure that aside from those very minor complications, the camera is now back to full working order.

Hanimex Rangefinder

p.s. my tooth still bloody hurts! Distraction failure.

4 Comments

  1. Oswin Dotzauer says:

    Hi,

    could you tell me, which battery needs the hanimex rangefinder?

    Best regards

    Ossi

    1. Dave says:

      Hi, I also need a battery for this camera. If you find out what battery it takes please let me know. Thanks.

  2. Dave says:

    Stephanie! Could you please tell me what type battery the RF35 takes. Thanks.

  3. Stephanie says:

    Hello Oswin, Dave,

    Oswin, sorry I somehow missed seeing your comment.

    I have a “28A” battery in there. This is an alkaline 6v battery, it’s about 13mm in diameter and 25mm long.

    I don’t actually know if this is the ‘correct’ battery. It fits ok and the camera appears to work correctly.

    Cheers!

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