Canon FTb(N) with sprocket issue (or: "how that QL feature is also a curse")

[Laurent]

Hello,

since I've been bitten by the camera repair bug, I tend to search for cameras with issues in the intent of fixing them.

So when I saw an FTb in a very good shape, and the seller saying "everything works except the broken sprocket", I could not resist!

Later I searched for documentation (which is a good thing, otherwise I might have refrained from buying this camera) and discovered removing the sprocket (or even accessing to it) is not a simple task due to the ... QL mechanism!

Documentation I used contains the Canon Service manuals (available in many places, including archive.org. Or ask me. I made a version with the separate guides in separate PDFs to ease navigation and allowing opening two at the same time). I also used the NatCam Canon FTb guide, but it is large and some information is lacking.

That "little" cover prevents any access to the sprocket. It is coupled to the QL articulated mechanism that makes the back impossible to easily remove.

The cover is held by screws, some of them being accessible behind the self timer mechanism, and some others behing the takeup spool...

The two screws behind the trigger bar have to be removed (self timer is already removed). This leads to removing the shutter trigger bar.

The trigger "bar" is in the little red rectangle...
Had I've been more clever, I might have saved some time... Note the "cam" at the bottom right corner has a notch in it, which allows triggering the camera but also allows removal of the bar without removing the cam...

The bar removal is somewhat simple, but it is needed to remove the "bird like" lever (second curtain release lever if I'm not mistaken) and the "Release lever". It will make your life easier if you note precisely how these relate to each other and to the rest of the camera.

Note that without this mistake my adventures would have been less challenging! My only regret is that I did not document each and every step, and it's hard to remember everything at the end.

Recommendation 1 (and note to myself) : if you want to fix a sprocket issue (or remove the QL mechanism) on a FTb, make sure the camera is wound before starting, and try not to trigger it.

Since I did not follow my own advice, I wanted to remove the cam, which turned when I wanted to remove the screw, which in turn (!) led to a camera in an undocumented state...

Recommendation 2 (and self note): be careful of the location of various parts, do not mislocate them (this sound better than "don't lose them").

 

[Laurent]

Once the trigger "bar" is removed, you can proceed to the next big thing: getting rid of the takeup spool.

(Late notice: I supposed you removed the winding lever and counter. If not, do it now.)

The spool runs concentric to the main winding axle, so the first thing is to remove this axle. For this, there is a small screw that serves as a coupling mechanism. it is visible just above the "E Ring" (I call them Circlips).

Then remove the E-Ring.Do not lose it, it may jump anywhere. If you lose it, it's no big deal, it's a pretty standard size.

The axle can then be removed.

The counter "cam" has to be removed, it's an easy job as there are three screws. Notice the position of the cam before removing it (or look at the NatCam guide to find it. ) Here it is in the red "box" I've drawn.

Removing the latch-release cam is necessary, so that the bottom nut can be reached. See step 114 of the NatCam guide.

Below is the "winding gear base" (Canon FTb Service Manual, page 30/31) that needs to go.

Finally (for now) the spool axle can be removed. You need two spanners, one of which has to reach deep enough to get the top part. Since I'm lucky enough to own a lathe, I made one myself. The interval between the pins is 9mm, pins diameter is 0.8mm 'cause it's all I had. 1 mm would do the job. I used Pliobond to keep the pins from falling.

Notice it has to be thin enough to get to the right place, and hollow so that the protrusion does not block the tool.

On the bottom I used my spanner wrench (the torque is a tad high, so it has to be held firmly)
The axle can then go.

Sorry, no image of this important achievement.

You deserve a break I guess!

 

[Laurent]

I just realized I did not cover the "basic stuff" like covers removal, or removing the mirror box. It's really the easiest part I think, so there's not much to be documented that's not covered in the recommended guides.

The FTb is very well designed, as for example the hotshoe connections use an intermediate PCB, from which you will desolder the 3 wires. There is a fourth wire (green) to unsolder, and this is an easy task.

I find easier to remove the selftimer/DOF/Mirror lift lever prior going further, a spanner wrench is needed to remove the screw. Do not lose the small parts (washers)

If you are better organized than me (not difficult, do not brag) you will keep the parts sorted in the removal order, so that putting them back is easy. Otherwise... you will lose time. The Canon guides show all the parts in the right order, so they are your friends.

Removing the leatherette has to be done carefully, I found isopropyl alcohol helps a lot, as does a painter's knife. I also used a very dulled screwdriver.

Once this is done (you need to remove the whole leatherette on the right side, I removed the whole leatherette on the rewind side but it's possible to peel it just enough to get access to the screws holding the mirror box) the mirror box can be removed, there are not traps there I think.

Screws are not all the same, one is visible when the camera is reassembled, so make sure you identify it.

To separate the mirror box from the camera, there is a tiny obstacle as the FTb(N) has a speed indicator, and the transmission cord ties the mirror box to the main body. Removing it is a bit fiddly but doable. At the end, you will have to reconnect it and reset the indicator.

I could have done without removing the prism but I wanted to have a look at the prism, and perform some cleanup. notice the "washers" (the red rectangles) position.

As a general comment, I think I've been too "shy" when opening the top, as the meter linkage rack tends to get in the ways, so I should have removed it at the very beginning. Same for the finder's lens. I ended up removing them at some point, so next time I'll save time and get them out at the beginning.

 

[Andreas Thaler]

 

[Andreas Thaler]

You can clearly see how high-quality SLRs were made at the time.

Metal throughout, which doesn't mean that plastic is worse.

That also explains the weight of these beautiful cameras.

 

[Laurent]

Trying to get back on track... I hope I do not forget too many steps...

So when the takeup spool and trigger "bar" are removed, it is now possible to remove the quickload mechanism after having removed the 4 screw that hold it.

Notice the mechanism is held in place by two cylinders that engage in two slots in the mechanism (see image below, the two lines point the cylinders). Using a screwdriver as a lever really helps removing the mechanism.

The back itself is held by three screws that are normally hidden under the leatherette.

The "fix" was easy there, as the sprocket issue was due to a screw gone "wild" (I found it at the bottom of the camera) and all I had to do was put it back. You can see it in the sprocket's slot in the first image of this post. I told my son at the beginning of this repair that I'd bet on a screw having gone loose and I was right...

Now we have to put everything back in place, and the real fun begins...

I took the opportunity to look at the various light traps, and changed one on the mirror box, as well as replacing the mirror bumper which really needed it.

 

[Laurent]

Reassembling is mainly putting things back in the reverse order, so I won't have too much to say.

I took the opportunity of a dismantled camera to clean as much dust as I could (surprisingly little, except at the very bottom of the camera, which had some sand there. Note that this is the third camera I open which has sand in the same place. Don't drop your cameras in the sane!)

An issue I had was that there are little ways of testing during reassembly as the camera is not in an operating mode and you don't want to mess things up too much (this was not my case, for example I had a cam rotate while removing a screw, so my camera ended in an undocumented state which caused issues later)

 

[Laurent]

Putting the mirror box back in place is a straightforward task, juste make sure the the screws are the right one (I wrote directly "small" for one screw on the mirror box, it's the smaller screw below the leatherette). The screw that's visible on the black painted part of the box is the one with a dome head.

The CdS cell has to be put back in place. Do not lose the ND filters, and make sure it goes all the way down.

The finder "window" can be put back in place.

The meter "rack" gets back in place, make sure to align the screw, the "scribe hole" in the rack and the hole in the pinion. This is true for a speed dial set at 1/1000s at ISO 100.

At the bottom of the camera the aperture striker has to be put back in place. Prior to this we need to replace a light baffle at the bottom at the mirror box:

Then we can put the lever in place.

I noticed the prism holder had a degraded foam, and also the prism "etching" had started to happen. So I made sure the foam was replaced (I use 2 mm foam from the light baffle kit) after the prism, its holder and the prim cover were perfectly clean.

The prism is then put back in place.

And finally locked by its holder.

I'll break there as the post becomes too long and harder to edit...

 

[Laurent]

A somewhat touchy part is putting the speed indicator (only on FTb(N) ) back in place.

The indicator is based on a small "chord" that links the speed dial to the indicator. Normally is you removed the chord you did it from the speed dial (note Canon recommends to avoid removing this, as it is an additional step to reset the indicator properly).

Make sure the dial is set to 1/1000 of a second.

Start by "charging" the indicator : turn the indicator wheel 3 turns in counter clockwise direction. Then you can release one turn while letting the chord wind around it.

The tricky part is to keep the chord wound while you put it around the pulley and then couple it with the dial. The path is: counter clockwise around the indicator's pulley, the "relay" pulley and the speed dial. Look at image below for an idea (sorry, it could be clearer. the chord is the white thing that goes around the pulley at the right bottom of the image)

Normally, when you are done, the indicator should be "somewhat" exact, but most of the time it will not be precisely set. The pulley is mounted on an excentric so that it can be adjusted.

I made myself a tool, as I had no wrench capable of fitting the pulley's excentric:

The tool is 0.5mm thick, 1 mm could do but I had that steel ribbon. It's a bit fragile, so 1mm may be a better idea if you plan on fixing several FTb(n)s.

To check the setting, I had the prism in place, and I checked the speed was properly shown from Bulb to 1/1000

I don't know is this indicator is a gadget, some people tend to say they prefer the FTb "Old" because it has less plastic parts. But I wouldn't be happy with a poorly set indicator.

Note that I had to remove the indicator again, and it seems to be harder to set, so the chord may need a replacement. Will see next time if I am to open this camera again.

 

[Laurent]

The DOF preview / Mirror / Self-timer lever has to be put back in place at one moment...

Start by putting the locking lever in place. Make sure it is in the right position (it clicks in place)

The NatCam guide advises to charge the self time in order to have the lever being "caught" when the mechanism is triggerred. You can also make sure you know what position it is in, that works. Then you can put the slotted washer in place, and then the lever.

Finally (sorry, no image) the stack of washers, the "indicator " dial and the screw that holds everything in place.

 

[Laurent]

Putting the top cover back is easy, there are a few details to take care of.

The speed dial couples with the white weel using a notch. The 1/1000 and 100ISO setting makes it couple with the front notch. Normally this was marked at the factory (the four notchs are not symmetric). In my case, I marked it again as the original mark was fading.

ng.

I started by the winding lever. Put the decorative disc in place (I used Pliobond to keep it in place)

Then put the coupling disc. Notice the small washer on top of the disc.

Then the winding lever.

Then the stack of washers and the nut that blocks everything in place.

The I put the speed dial back

and the holding screw

And finally the trigger lock lever. It is held by two screws.

On the rewind side, simply put the rewind lever in place.

 

[Laurent]

Soooo... as I said earlier, be careful not to jam the camera by moving any cam. If you did not, the you will end with a jammed camera and have to find a way to unjam it.

In my case, I used the working TX as a model, and tried to do my best. What follows is more a discussion than a guide, and I do not guarantee the chronological order, nor the method.

In the image above, the TX is at the bottom (marked on the tripod plate). Notice I broke a screw on the FTb (top camera, right part of the image). I therefore used the "sacrifice" camera as a donor (it's another FTb I bought for the prism and which has too many issues for being repaired, from a broken mirror, twisted mirror frame, to corrosion in many places, to damaged light condenser in the finder, and a shutter into someone seems to have pushed a finger...)

The "only" issue is that by breaking the screw (my intent was to free the place so that a lever could be put in the right place) I had to remove the gear that carries it, which in turns makes me remove some other levers... The winding cam was also removed, and is already in place here.

some levers are missing in the middle...

As there are several levers stacked together, and some springs, the exercise is interesting... I found easier to put everything together outside of the camera before getting them back.

They will do everything they can to get loose again... be warned! Most of the time, I find MUCH easier to put the assembly in place with "uncharged" springs, then charge the springs later.

Notice the position of EVERY lever. The one at the top of the image is barely visible as its pivot is on the front of the main casting, but it has to be below the big one in the middle of the camera, and below the very small one at the left near the trigger post.

You can see it from another angle, the pivot is not in place, nor is the screw that holds it

The small spring that pulls the two levers in the winding cam (center of the image) was secured with Pliobond, so I put Pliobond to hold it in place.

I'll assume that, if you managed to jammed the camera, you now have a working camera!

 

[Laurent]

... in my case, that lasted until I ran a few tests, and got the winding lever blocked, with the shutter half cocked.

The culprit was the winding cam, which move as I did not lock the nut tight enough... It took me a few hours to find out, until I noticed the "clutch release lever" (the very small lever near the trigger post), that the cam was no longer properly seated in place.

Sorry for the bad quality, I noticed it later, and will definitely NOT jam the camera again for a better focus

So I removed the small lever, then the second curtain winding cam (small cam below the spring) then the nut could be retightened. I marked the different positions before removing the parts, and put them back in the same position. These camera's design is so good that the mechanism went back in sync after that.

 

[Laurent]

Sometime during this process, I replaced the foams, and this is another reason why the QL can be a curse! The foam near the hinge of the back interferes with the QL plates, so it is a bit tricky to put it there.

Leaving the paper on most of it really helps, then you can peel it from the foam and put it in place.

Before removing the light traps from the back of the camera, I protected the shutter with a piece of business card, as the gunk is not easy to remove and I fear damaging the shutter cloth is not a good thing...

At this stage, the camera was (notice the past tense!) ready for a test.

If you've seen my other post about FTBs being noisy when winding, you may foresee a sequel, as I have to fix the takeup spool...

 

[Laurent]

So... this is the sequel!

The morale first: next time I'll be more cautious... the coupling between the takeup spool and the axle uses a specific washer, which has to be nested in the spool. I guess I did not put it properly, which may explain why I had issues putting the "E-ring" back when I reassembled the winding mechanism. I "solved it" by tightening the nut, but I guess this interfered with the clutch that makes the spool slip when winding or rewinding.

On the image above the slot is obvious...

Since I removed the spool again, I took the opportunity to clean and adjust the clutch.

(That one is for @Andreas Thaler , it shows one of the signs of wear on the camera... there aren't a lot!)

Then I reassembled the mechanism.

The little screw locks the nut in place. When testing was satisfying, I locked it using some screw securing "glue" (Frein Filet in French, ref 243)

The "scientific" test used some string, a fisherman's lead, and a vise. I checked the spool could barely hold 290g (the manual recommends 280 to 400 g and I wanted to stay on the safe side (and had no appropriate lead for more than 290)

The final test was that I ran a film through the camera, and when I was happy I did the same but with the back open so that I could mark the distance and check afterwards...

I put some film though it again, just for a final check, and this is THE END for this project! (Next project should be another FTb, not "N" this time, that should become a "Panda" (black FTb initialy, top cover badly damaged, the plan is to use the cover and base of a chrome FTb that already gave parts to my TX and this FTb)

If there is something this project taught me, it's that a CLA is worth every cent, even if it costs more than what the camera is "worth".

(The camera is now for sale, I'll put an ad on Photrio also, of course)

 

[Andreas Thaler]

Excellent work!

 

[Laurent]

Excellent work!

Thanks!