DIY Repairs

This page is intended to give some guidance to anyone wishing to attempt their own repairs. It doesn’t detail everything possible and probably never will but it should get you started at least. The page does get updated occasionally as I get to record and write up more things.

Needless to say, anything you do to your camera is at your risk even if you are following my instructions.

What this page doesn’t include is any fault finding help (well, not much anyway). The Contax 139 service manual gives a comprehensive list of possible causes of various symptoms and I suggest you refer to that if the cause of your problem isn’t obvious. The Contax 139 Service and Assembly manuals can be viewed and/or downloaded from these links.

Repair manual

Assembly and parts manual


Most repairs will require some degree of dismantling of the camera so it makes sense to start with the basic top cover and baseplate removal.


Not a lot to say about this. There are three screws which, when removed, allow the baseplate to come off. The only things to watch out for are the rewind release button cover and the plastic surround from around the tripod bush, both of which are loose and will likely fall out once the plate is removed. The plastic surround was only fitted on later models so don’t worry if yours doesn’t have it.

Top Cover

First thing to remove is the shutter release button and ISO speed dial. The release button unscrews but, of course, there is nothing to catch hold of. The technique is to use a rubber pad pressed down against the button or, as I prefer, a latex glove stretched over the end of a finger, to grip the button and turn it. They can be difficult to undo, especially if they haven’t been undone for some time. If you find you can’t get enough grip onto the button, try a small piece of double sided sticky tape stuck onto the button.

If it’s still not possible to unscrew the button, try the following method. Rotate the compensation dial to ‘4’. Apply a piece of double sided sticky tape to the button, overlapping it onto the surrounding dial. Using a latex glove or similar for extra grip, press down on the button with your thumb and then rotate the whole dial counter-clockwise to the ‘¼’ position (you’ll need to hold in the compensation dial release latch while you do it). Most times, this will rotate the shutter release button as well. If it doesn’t do it at the first attempt, try it again with a new piece of tape. I’ve never yet had this method fail.

With the button unscrewed, the ISO dial assembly can be lifted out. There’s no need to dismantle the ISO dial assembly unless it requires cleaning or has some problem with it.

Next remove the rewind knob. This unscrews from it’s shaft. Undo the camera back and insert the blade of a screwdriver, or something similar, into the fork on the bottom end of the rewind shaft. This will stop it from turning so that the knob can be unscrewed. There is usually a washer under the knob though sometimes this maybe missing.

With the rewind knob removed, unscrew the three screws in the shutter speed dial and lift off the dial. It’s worth noting at this point what speed the dial is set at (I usually set it to 1000th) so that the dial can be put back on correctly.

Next remove the film advance lever. The rubber insert on top of the lever is stuck on. Lift a corner of it first and then pull the whole insert out. Undo the screw which is found under the rubber insert. This screw has quite a narrow slot so make sure you use a suitable screwdriver or you’ll damage it. This screw has a LEFT HAND THREAD so unscrew it CLOCKWISE. With the screw out, the lever can be lifted off. Underneath is a washer, it may be flat or domed, with two slots in it’s edge. One of the slots will have the end of a spring engaged in it. Disengage the spring and lift off the washer. Underneath is a collet with a slotted top. Unscrew the collet using a wrench. The spring around the collet is hooked into a slot in the top cover and will come out once the collet is unscrewed.

Remove the trim from around the remote release socket. Use a piece of rubber to press against the trim and then unscrew it.

Now remove five screws holding the top cover in place. One is near the shutter speed dial, two are either side of the viewfinder and two are either side of the lens mount. Note the two by the lens mount are longer than the others.

Now the top cover can be lifted off.

Lens Mount Trim

With the top and bottom covers off, the trim around the lens mount can be removed. Two screws at it’s bottom edge, normally hidden by the baseplate, hold it in place (later cameras often only have one screw fitted and I have found some with none at all). It’s not always necessary to remove this but, if the two front plates of the camera need removing then the trim needs to come off.

Front Plates

There is a plate either side of the lens mount that can be removed. To do so, the front covers need to be removed first. Under the right hand cover (looking from the front) is the exposure adjustment and also the flash voltage adjustment. The exposure adjustment has a hole in the front plate to access it so it’s not necessary to remove the plate. On later cameras, the flash voltage adjustment also had a hole through which it could be adjusted. There’s not much else under the right hand plate of interest unless you have shutter release problems which have been traced to the shutter release magnet. The connections for the magnet are under this plate and some checks can be carried out. But the magnet itself cannot be reached.

The left hand front plate carries the exposure check button and self timer switch. A small PCB on the back of the plate makes contact with some spring contacts in the body allowing the plate to be removed. Removing this plate allows better access to the mirror damper flywheel which sometimes squeaks and needs lubricating. The shutter magnet (not the release magnet) is also under this plate if you need to access it.

Often, the front plates don’t need to be removed so leave them unless you really need to remove them.

Electrical Contacts

Electrical contacts are always a potential source of problems. All the contacts in the 139 are gold plated and are generally pretty reliable but I have seen some problems and always make a point of cleaning all of them if I repair/service a camera. I use a fibre glass pen made for the job. They are like a propelling pencil but have a bundle of glass fibres instead of a lead. When rubbed over electrical contacts it does a good job of removing any dirt and oxidisation. If you don't have one, cleaning the contacts with isopropyl alcohol (IPA) does almost as well.

Electrical contacts exist at the shutter speed dial, the ISO dial, the left hand front plate (exposure check switch and self timer) and the later versions of transfer switch under the base plate.

Shutter Speed Dial

Once the top cover is removed, the shutter speed dial click plate assembly is removed by removing the rewind shaft holder nut then disengaging the spring from the click lever assembly then moving the lever out of the way, or lifting it off, so that the click plate can be lifted off the shaft. Underneath is a PCB with several gold plated tracks. They all should be cleaned. Also the spring contacts which are attached to the underside of the click plate.

ISO Dial

The ISO contact plate assembly has three metal disks mounted over it. They are related to the exposure compensation setting and are referred to in the manual as Corrective Click Plate, Corrective Lever Guide and Corrective Lock Plate. They all have various cut-outs and notches in them and may look symmetrical, but they aren’t so before removing them I suggest marking the top side so that you know which way up to put them back on later. You can see the marks I’ve placed on them in the picture. (In the picture the top one has already been removed).

With the ISO contact plate removed, clean the carbon track with IPA. Don’t use anything abrasive on it like the glass fibre pen previously mentioned. Clean the spring contact on the underside of the contact plate.

This picture also shows the spring contacts that connect to the left hand front plate assembly. Clean the spring contacts and also the mating contacts on the rear of the PCB which is attached to the back of the front plate.

Transfer Switch

The transfer switch is located under the base plate. There are three different versions that I know of. The original one is a blue microswitch which is sealed and can’t be cleaned. The two later ones use open contacts and should be cleaned.

Shutter Release Switch

The shutter release switch consists of a domed metal disk sitting on a printed circuit board. The pin attached to the underside of the release button sits on top of this domed disk and, when pressed, causes the centre of the disk to come into contact with the PCB. Problems can be caused by dirty or oxidised contacts or by distortion of the domed disk.

If the shutter release needs excessive pressure to make it work, or it doesn’t work at all, then dismantling the switch and cleaning it is usually a first step. When dismantled, it’s also possible to check the domed disk isn’t distorted.

To remove the switch, the ISO plate needs to be lifted. Refer to the section on lifting the flexible PCB to find out how to do this. With the ISO plate lifted, the switch, which is on the underside of the plate, can be dismantled. First remove one screw that holds in place the row of contacts that mate with the front plate and move them aside. Then remove the two screws (usually sealed) that hold the switch cover in place. The parts of the switch, in their correct assembly order, are shown in the picture.

Film Advance (Wind-on) Mechanism

I don’t recommend anyone dismantle the film advance shaft assembly (parts diagram No 4 in the manual) unless absolutely necessary as there are several pitfalls to doing it (like a bunch of very small ball bearings that will shoot everywhere) and there’s nothing that is likely to go wrong with it.

The film advance mechanism is usually pretty reliable. I’ve rarely had problems with it.

Squeaky Shutter

Actually, the shutter doesn’t squeak - the problem is the mirror damper flywheel and the solution is to lubricate it. The flywheel is located on the left side of the mirror box. I lubricate both the flywheel shaft and the shaft of the gear above it. Use only very light oil.

Lifting the Flexible PCB

In common with many electronic SLRs, the 139 has a flexible PCB (flexi) which wraps itself over the top of the prism. This means it has to be lifted out of the way if access to the prism is required or to remove the mirror box. Here’s how to release and lift up the flexi sufficiently to allow either of these.

Before starting to release the flexi, remove the top and bottom covers, also the lens mount trim and the left hand (looking from the front) front panel. Also remove any batteries to eliminate power to the flexi.

Start by desoldering the wires to the shutter. There are three wires - brown, yellow and black.

While you have the soldering iron in your hand, also desolder the brown wire that comes up from the flash socket.

Also desolder the green wire from the remote release socket. Once that’s done, the exposure compensation indicator arm needs removing by releasing the snap ring fitted to the top of it’s pivot. Before removing the arm, note how the hair spring that protrudes from the arm engages with the indicator flag.

Next remove the metal clip that retains the wires that go to the shutter and also acts as an anchor point for the spring that is attached to the exposure compensation lock lever. When removing the clip, unclip the spring from the lever (green arrow below) and leave it attached to the clip.

The ISO dial plate needs to be released by unscrewing the three retaining screws and also the exposure compensation indicator arm pivot. Note the spring hooked around the larger, black, screw. The spring won’t come completely off so no danger of losing it, but just note it’s position.

Now the ISO plate is free and can be lifted but the flash contacts are still preventing the flexi from being completely lifted away. (Note the contacts hanging from below the ISO plate. These contact the front plate. They are delicate and easily bent so be careful).

To release the flexi at the flash contacts, first remove the viewfinder surround by unscrewing the two screws and pulling it away (note that the viewfinder lens is now exposed so take care not to scratch it). Once the viewfinder surround is removed, unscrew the three screws holding the flexi in place.

Now pull the SPD out of its slot then lift the flexi off the three pegs that sit up inside the three springs.

The last thing to remove is the viewfinder display LED assembly that is attached to the side of the prism assembly. There is one screw holding it in place. The two slotted screws that can be seen either side of the fixing screw are used to adjust the position of the assembly to align the LEDs with the viewfinder mask.

With the fixing screw removed, fold back the flexi and gently lift the LED assembly out of its slot.

The flexi is now fully out of the way of the prism and mirror box assembly.

Reassembly is reverse order. Adjust the viewfinder display LED position by adjusting the slotted screws previously mentioned while looking through the viewfinder with the LEDs lit. Check the top most and the bottom most LED.

Removing the Mirror Box

It’s necessary to remove the mirror box assembly to get access to the shutter or to carry out repairs to the mirror mechanism. The most likely reason for doing it is to get access to the release magnet which is underneath the mirror box.

Remove all the covers including both front panels. Release the flexi as described above.

Unsolder the wires found underneath the right hand front panel. The red wire can be left connected but all others need to be disconnected from the flexi.

Unscrew the two black screws under the lens mount.

Unscrew the two screws either side of the viewfinder.

The mirror box can now be pulled forward. It may need a wiggle to get it clear.

Replacement is the reverse order but, before refitting the mirror box, cock the shutter by using the film advance and cock the mirror by pushing the lever shown in the next picture in the direction shown until it locks into place.

Cleaning the Release Magnet

The release magnet is a combination magnet (common in electromechanical cameras) which consists of a permanent magnet but with a coil as in an electromagnet. The field created by the coil is in opposition to the permanent magnet so effectively cancels the permanent magnet. This arrangement is often used to hold a mechanism in a particular state without the need for continuous current flow. A pulse of current is used to cancel the holding magnet and so release the mechanism.

A common problem with combination magnets is the armature sticks to the magnet due to dirt or contamination. When this happens, the armature fails to move when the magnet is turned off and then nothing happens. This is one of the more common problems with the 139.

To clean the magnet which is under the mirror box, refer to the previous sections to remove the mirror box. With the box out, underneath you’ll find the magnet covered with a plastic cover.

Unclip the plastic cover and cock the mirror (see previous section). It should now be possible to move the armature away from the magnet but remember the permanent magnet is still holding it and, if it’s also contaminated, it may need a little force to move it.

Now clean the mating faces of the magnet and the armature. The following pictures show a contaminated magnet armature before and after cleaning.

Refit the cover to the magnet before reinstalling the mirror box.

Addendum: There are two versions of the mirror mechanism (that I know of) so what you see under the mirror box may be slightly different than that shown above - but the principle is the same. The later mechanism has a cover on the magnet that can’t be totally removed without further dismantling but it can be unclipped from one side and moved forward enough to clean the contacts.

Manual Shutter Release

A little known fact is that the 139 has a mechanical shutter release. It’s only there for service use and isn’t something that can normally be accessed - but I thought it worth mentioning here.

The release is under the mirror box but can be accessed without too much dismantling. The bottom cover and the lens mount trim need to be removed to access it.

The release is a small lever that protrudes from just under the mirror box, towards the front, on the right hand side when looking at the front of the camera.

Here’s the lever shown with the mirror box out of the camera. Move the lever in the direction of the arrow to release the shutter. This basically does what the release magnet armature would normally do.

This is what it looks like with the mirror box in place.

Cleaning the Focus Screen

When looking through the viewfinder, any specs of dust that are visible and are sharpley focussed are on the top of the screen or the underside of the prism. To clean these off requires removing the prism. Any specs that are visible that are not in focus will be on the underside of the screen and it may be possible to remove them with a blower. Any smudges are likely to be the result of someone making an attempt at cleaning the screen in situ. Usually the fresnel lens, which is on the underside of the screen, becomes damaged and nothing can be done with it.

Any sticky marks, possible caused by perished mirror damper foam, can usually be removed but the screen should be completely removed from the camera first.

The focus screen is not user removable and to remove it requires the flexi PCB to be lifted and the prism removed from the top of the mirror box. The prism comes out in a frame which also holds the focus screen. The prism needs removing from the frame (it’s stuck in place) and the screen can then be removed for cleaning. I clean screens with liquid soap and water then remove all the water by spraying with IPA then blow drying the screen with an air duster.

NEVER try and clean the screen in situ. You’ll only make it worse.

Mirror Stop (and Focus Errors)

The mirror stop is located in the mirror box (arrowed in picture) and the mirror rests against it when in the down position. The position of the stop is adjustable to make fine adjustments to the focus. The stop has a rubber (maybe plastic) piece around the end of it for the mirror to rest against and this can sometimes come off.

I’ve seen several instances where it has split and so become loose and then fallen off.

If the rubber piece is missing, there will be a serious error in the focusing so, if it’s found impossible to focus on infinity, check this piece is in place. The other problem, if it’s missing, is the mirror will hit the metal part of the stop if the shutter is fired and this can result in a broken mirror. Here’s the evidence…

and so to…

Replacing the Mirror

This section has been deleted and a new page about mirror replacement has been added to the side menu.

Adjusting the focus

Note: If adjusting the focus after mirror replacement, use the method described on the mirror replacement page to check the focus and use this section for how to make the adjustment.

It’s rare that the focus should need adjusting but it’s worth checking after replacing the mirror or if the whole mirror box has been replaced. Check the focus using a focus screen or a ground glass screen at the film plane, checking it against the focus seen in the viewfinder.

WARNING: getting the focus correct is extremely difficult. I suggest not attempting this unless you are absolutely sure there is a problem.

To adjust the focus, remove the base plate and the cover from around the lens mount, also the right side (looking from the front) front cover.

It’s not absolutely necessary to remove the cover as the focus adjust screw can be seen without removing it, but access to is much easier if the cover is removed to give extra room.

The focus adjust screw can now be accessed.

NOTE: There are two screws close together. It is the bottom screw to adjust focus. DO NOT adjust the other screw as this changes the angle of the mirror.

This shows the position of the screw more clearly.

Shutter Second Curtain Brake

There is one issue I have experienced with the shutter on a couple of occasions but the symptoms can vary. The problem is with the catch, or brake, that catches the second curtain at the end of its travel to stop it bouncing. If it isn’t working then, obviously, the curtain can bounce and can cause a band of overexposure along the top of the negative (bottom of the image). The other symptom can be that the mirror fails to return. This happens if the catch prevents the curtain from completing its travel so the shutter never gets to the point where it releases the mirror.

This picture shows the shutter cocked and the catch (ringed in red) open.

This is after the shutter has been triggered with the catch closed as it should be. Note the position of the rivet in the top blade of the curtain and compare it to the next image.

This is the catch not fully closed and preventing the shutter from fully closing. See where the rivet has finished up.

The solution is to remove the catch by unscrewing the screw (note the washers and their positions) and cleaning the faces of the catch and the washers as they will probably be gummed up. Note that the catch needs to be tight for it to work correctly just not too tight. If, when you get the screw set correctly for the catch to work, it seems too loose, put some loctite (threadlock or similar) on the thread to stop the screw coming undone in the future.

The above can be done with the shutter still in the camera once the mirror box has been removed but below is how to remove the shutter if you need to.

Shutter Removal

Remove the mirror box as detailed above. There are three screws holding the shutter in place. Two are accessed from inside the camera and one from the back. See the two pictures below.

Note that one of the two screws inside the camera is coverd by the multi-exposure arm so remove this first by unhooking its spring and removing the screw.

The shutter can then be removed.


Reassembly is, generally, the reverse order of disassembly but there are a few of things worth specifically mentioning.

Alignment of viewfinder LEDs.

If you lift the flexi to get access to the prism or to remove the mirror box, you will have removed the screw that holds the LED display in position. The two, slotted, adjustment screws don't need to be touched and the display might go back into it's original position - or it might not. Once the camera is in a state that the LEDs can be turned on, check they align with the viewfinder mask. I find the best way is to set the shutter speed to B so the lowest LED is turned on, then point the body at a bright light so the uppermost 'Over' LED also comes on. You can then make any necessary adjustments if the two LEDs are not fully in view. There's more information in the service manual regarding which adjustment screw to turn to move the LEDs in a given direction.

ISO dial assembly

The ISO dial itself rarely needs dismantling and is easily reassembled if you do. But the various plates that fit under the ISO dial are less intuitive to reassemble and, unless you take careful notes when removing them, you will likely not get them back in the correct position. So here's a step by step reassembly guide.

It easiest to reassemble the plates under the ISO dial before refitting the top cover. The ISO dial itself has to be fitted after the top cover.

Hold the two pawls out of the way and fit the plastic contact carrier.

Fit the Corrective Lock Plate making sure the lower pawl engages with the slot. Also make sure the shorter of the two curved slots in the plate is nearest the prism.

Fit the Corrective Lever Guide as shown.

Finally fit the Corrective Click Plate, again making sure the shorter of the two curved slots is nearest the prism. Apply a little light grease to the edge of the plate where the pawl engages with it.

Now, temporarily, fit the ISO dial. The white alignment mark points towards the prism.

Make sure the tang that hangs below the ISO dial couples with the slot in the plastic contact carrier. This makes sure it will re-engage when you fit the ISO dial after fitting the top cover (assuming the contact carrier doesn't move of course).

Now remove the ISO dial and continue with fitting the top cover.

Multi exposure switch

The multi-exposure switch, which also unlocks the exposure compensation dial, engages with two levers, one for each function. When refitting the top cover, it doesn't always fit in its proper position behind the two levers but instead gets caught up on top of them. Check the switch moves freely when the top cover is refitted and, if not, try again or use a thin tool through the ISO dial hole to move it into place.

Note: a recent instance of this gave the symptoms of the camera failing to fire. This was due to the multi-exposure lever being caught up and stopping the film advance mechanism from fully returning to its normal position.

Fitting Covers

The final thing to do after most repairs is to refit the covers. Or maybe you just want to fit new covers. They’re not difficult to fit but I’ve seen many that have been badly fitted so this is how I do it. I generally use self adhesive covers but, if not, I use double sided tape to stick the covers on, applying it first to the cover, then trimming around it, then applying it to the camera.

Remove any old adhesive and clean the surface with an alcohol based cleaner to degrease it.

I start with the right front cover (looking from the front) as that’s the easiest. Remove the backing paper and wet the adhesive surface slightly (I use a licked finger) of about half of the cover that will be nearest the lens mount. Slide the cover up against the lens mount and make sure it’s square and sits between the two edges neatly. If it isn’t, lift it and try again (the wetting of the surface will allow you to lift it or make small adjustments before it completely sticks). Press down the cover working towards the corner of the camera. Press the cover around the corner but not completely. When the cover is nearly all the way down, press the corners of the cover into position then smooth the cover in towards the middle. This ensures the corners and end of the cover fit neatly.

The left front cover is the same procedure but it’s a bit more difficult because of fitting around the meter button and self timer. Making sure the back is slightly wet makes a big difference here because you need to slide the cover into place.

The back cover is the most difficult as it fits around the film memo holder. The cover needs to fit under the edge of the holder and the original covers were thinner so they could fit. Replacement covers are often thicker and are difficult to get under the holder. Check the fitting of the cover first to see if it will tuck under the holder easily. If it does, then, again, making sure the adhesive is slightly wet will make fitting the cover much easier and it may be possible to get a god result. However, I always remove the film memo holder completely before fitting the cover. The holder can be quite easily removed using a flat, blunt, tool (I use the handle of a pair of tweezers. Slide the tool into the top of the holder and twist it to lift the holder.

Work your way around to lift all four corners.

With the holder out of the way, fitting the rear cover is much easier and there’s no risk of getting it kinked trying to get it to fit around the holder.

Fit the cover starting from the middle. Position the cuttout equally around the memo holder fixing holes (remember to wet it first).

Once you’re happy it is central and square, start pressing it down towards the outside edges and finish it off in the same way as the front ones.

To refit the memo holder, clean up the plastic rivets that will have pulled through the holes. Press the holder back into place making sure the rivets fit back through the holes and the holder is all the way in. Remove it again and apply a small amount of glue to each plastic rivet then refit again. I recommend a glue such as Evo-stick as it allows the holder to be removed again if needed in the future. Whatever you use, don’t use Super Glue (Crazy Glue).