24-105 F4 IS – damaged stabilizer

A few weeks ago I repaired a used 24-105 for myself. I have purchased it in a box in thousand pieces for a bargain price. Everything was ok – excepting a strange noice from the stabilizer when switching on and off. Does it work – yes.  Does it have any fault symptoms – not.

Excepting the fact, that the photos were blurred.

When I checked it thoroughly, I observed, that stabilizer was working only within  a tiny moving field. The brake didn’t engaged the moving of the stabilizing lens element. Checking this is not too difficult, and IS A MUST AFTER ANY REPAIR. Watch through the lens and the camera to an object, and move the body (like small oscillations with the lens up and down, or left to right. Case the shutter is not pressed, the object will move in the field of view. Case the IS works (button halfway depressed), the image will not move in the viewfinder, better to say, only after making a bigger amplitude.

Simple.

My one moved always, just after switching on the IS movement was a little bit less..

After disassembly of the lens: I have seen nothing. After disassembling of the IS unit, I had a feeling, that the small motor for the bake moves sticky.

   

And watching through my favourite 20x stereo microscope, i have seen, that the small white gear has been damaged. One teeth is deformed. And that was enough to stop the brake ring.

Fortunately I had an another bad unit in a box (electronic failure). So I changed the electronic/cable on them.

    

Is not too easy to get out the flex from this type of socket – I used some adhesive tape on the cables back, and I pulled then the tape, not the cable.

But be careful – the upper lens element has to be centrated after disassembly and assembly.

Just an another trick: the aperture flex cable always brakes in the same position.

At first, as I told in another post, cut the sharp edge of the last lens element to a round form.

Then put some textile-base adhesive tape on the flex cables back side.

 

 

Never forget to check on a repaired lens:

– the aperture on any zoom position
– the focusing on any zoom position
– the zooming
– the stabiliser switched off/on.

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Dust blow gun – compressed air

I know, that there is possible to work with a hand-pump too – but trust me, the difference is HUGE. If You work with 2-3 bar, or special cases 5-6 bars, any solid contamination will be eliminated.

At first, You will need an oil-free compressor, if possible a silent one. After this, a filtering – there are cheep and expensive solutions. then a flexible hose, and of course a dust blow gun too. (Before I had a normal one – placed in the basement because of the 97 dB (!!!) noise.)

Here You see, what I use at the moment, this is as noisy as a washing machine:

  

http://www.dolphincadcam.hu/HBM_Kompresszor.php

 

http://www.ebay.com/itm/311347833067?ssPageName=STRK%3AMEBIDX%3AIT&fromMakeTrack=true

 

 

http://www.ebay.com/itm/1-4Blue-Pro-Mini-in-Line-Air-Filter-Moisture-Water-Trap-Paintwork-Spray-Guns-/371415361828?hash=item567a14a924:g:NcoAAOSwPcVV0bJr

 

http://www.ebay.com/itm/Lightweight-Mini-Dust-blow-Gun-Dust-Blow-Removal-Model-Tool-Black-/302110408998?hash=item46572f0126:g:wt4AAOSwmLlYBRm9

 

Unfortunately the air gun is not a Swiss quality , so at first I had to disassemble and reassemble it.

The PH00 screwdriver – the MOST impotant tool for us

Theoretically Canon uses a JIS standard screwdriver. I had bought one for a LOT of money, and… it was worst, that the PH00 screwdrivers. So – nevermore.

But which PH00 screwdriver, if you need one?

 

Kopiowanie i przetwarzanie bez pisemnej zgody firmy http://www.tme.eu zabronione.

I can advice you this:  WIHA 00152  

Just to understand, in the last years I have tried a lot of different ones:
UNIOR – good price, small handle,
BETA – expensive, too harde, broken in a short time
some noname – nevermore
Neo-Tools – very good geometry, thick handle, but no possibility to by only the bit. The gibe 25 years of warranty 🙂 , and I changed back 2 times the bit after breaking it, which is a good sport, but too much time.

The WIHA has a good price – 5 EUR – and there is available in Conrad shops.

But for some special cases you will need a torque controlled screwdriver. Her is my newest tool – and it is WONDERFUL. You can adjust the max toque, when you reach that, will vibrate and will generate a beep sound, but if you turn more the screw, will display the maximum reached value. Is very helpful.

Sealey Torque Screwdriver Digital Readout 0.05 – 5Nm 1/4″ Hex Drive STS103

 

You will need a PH00 1/4″ bit too – try this:

Kopiowanie i przetwarzanie bez pisemnej zgody firmy http://www.tme.eu zabronione.

WIHA 31961

 

 

Polishing a damaged lens – cerium-oxide

Normally I repair only Canon DSLR-s – but sometimes I cant resist to other optical devices either.

I had to clean a DLP (!)  video-projector for my sons school – it was terrible, a half kg of dust in a small box, lenses, the rotating colour filter – EVERYTHING full of dust. After compressed air i used some alcohol, to clean the optical elements. In normal cases I use pure methanol, its cheaper than ethylic alcohol, and much better  properties. And I always check at first the surface, if tolerates the solvent. I have done exactly so – excepting the LAST lens – a very funny lens, which is part of the condenser lens system.

I shouldn’t. It is a plastic lens – and immediately after wiping with the cotton swab has got a matt surface. And I observed this only on the second surface.

Hrrrrrrr. The lens has a special form, no chance to purchase a used one.

So, there was only one possibility remaining: to polish the damaged surface. Unfortunately one surface was non-spherical.

 

You can see the scratches on the surface – and some waveforms too – so it was absolutely unusable.

One thing was to get back the shiny surface – the second to get out the waves. I needed a negative form for polishing, plus a polishing material. The ordered cerium-oxide didn’t arrived at time – but i have found a 3M material, which I have got months ago, without any technical specification. Worst could not be – let’s try it.

To make the negative, I covered the lens with a thin polyethylene bag, and as a form material I used Poxipol, a cheap but very good 2K epoxy-glue.

  

You can see in the section, that one surface is spherical, the second not.

  

The foil has protected the surface. I wanted to make the polishing with rotation – so I used a small grinding stone on a shaft as a support.

   

The glue hardened in a short time (10 min + 10 min for security), and after separating them, and peeling off the foil, I have a PERFECT negative of the lens. As You can see, the lens is not completely symmetrical – but this will not count, as I will rotate it, so the lens will be polished on the whole surface.

  

I used an optical cloth for a polishing compound carrier, the green fabric.

  

The small tool has 130 W power (230V), and is not the best quality, but for that price it’s perfect. after the rotating polishing, I had to make it manually too, on certain points of the lens. And yes, after doing this, I was like a pig on a farm. Just white.

The polishing compound is: 3M 60150, used in the car industry, for window repairs.

And the lens is PERFECT, the projector works, and I am happy .

F-words repairing Canon lens

F like F…. FLEX. The f.cking flex.

I had to repair a 17-55 with aperture problems. The lens started to close the aperture more and more at certain zoom values.

Simple case, isn’t it? You have to change the flex. As on the shelf I had only 1 pcs of this cable (there are not too many such cases), I worked very carefully. Before disassembling the aperture module, I made a small testing assembly: the board, the stabilizer and the aperture module, connected to a camera (an old 40d) wih an extension cable. Be careful: by this lens the aperture will not work without the IS connected!

The aperture was not working, better to say, working only when the cable was bent in certain manner. So, broken cable. (by the way: absolutely no visual signs of broken lines!)

I changed the cable, cleaned all the elements, degreased and re-greased the whole assembly. I always check the coils with the multimeter. (ca. 17 – 19 ohm)

After finishing the WHOLE work, I have done the final check: aperture was not working. F.ck, f.ck, and again f.ck! I have no time at all, and now I have to disassemble it again.

I had an another old aperture unit, which was considered bad and replaced with a complete one. Has the flex too (just not in perfect condition, as it has been disassembled from the lens.

I checked it with the “test bench”. Not working – but in an other way!

The aperture has a small stepper motor, and an optocoupler,  which gives the ZERO (open) position. The basic position is the most open one – and then the small black “flag” interrupts the light.

There can be 2 possible failures:

– No interruption at all (when sensor is dislocated, as the flag can not interrupt the beam). In this case the motor will bring it back to the start, but, as gets no ZERO signal, is buzzing till the electronic timer will stop it.
– ZERO signal all the time: for example no grounding of the interruption signal, because a damaged optocoupler – or a broken wire.   The optocoupler is in fact a npn transistor without a base. In this case the motor will try to open more and more the aperture, as the feedback line gives the information that is at the starting time all the time.

The disassembled old unit had a dislocated coupler. I pushed it into it’s place – and was working perfect.

The repaired lens module was bad with the symptom 2. – I was sure that the coupler didn’t survived the soldering.replace the repaired modules cable to a new one – so I desoldered the cable from the bad one, resoldered on the other (as I had no second cable, as i told)

(By the way: I tried to replace the bad optocoupler with one from an old 18-55 lens. On the photo the left one is from the 18-8, the right one is the original 17-55 assembly. It does not fit 100%, there is ca. 0.3 mm difference, but after working on it with some sandpaper was ok. I am sure from the function they are similar. At the end although I decided for the complete replacement)

I am a convinced atheist, but I must say THANKS GOD there was there the test bench. I checked it – not working.

After a half an hour of desperate measuring I had the explanation: the BRAND NEW cable was defective.

Now I am here, crying on the edge of the table, I will have to spend the whole time again for this work (totally: 3 complete repairs!!!)

 

When the brand new flex should be checked for continuity that is the end of the world.

I am sad.

 

Appeal:

Dear friend! When You reached the end of the page, means that you are interested in this subject. Case You are a native speaker, and You would like to help me spending some time, may I ask You to help my work by correcting the text from the point of view of the English grammar? If yes, just email me the corrected text – You would make me very happy.

Glued screws – when the serviceman get’s angry

I have got a Sigma 300 mm F2,8 lens from a customer, which has some dirt in the inside. A lens element was dirty or some fungus on the surface. (As a supplementary information I was told, that on the lens somebody made a “screw-exchange”. Ok.)

Not a big deal.

Normally.

When I wanted to open the screws which hold the barrels on the back side, I have seen, that the 3 screws are of 3 different types. Hmm.

Unfortunately, the head of the screw was not too strong. After a few trials broke the head – without any movement of the thread.

  

And after this I observed, that the screws were glued into their places. Beautiful.

As at this moment I had to take out them anyway, started a fight against the glue. After approx. 20 minutes one screw was out – and another has no more slot in the had. And I had less with one expensive screwdriver bit, which also has broken during the operation.

Now there was only one way: to drill out the head without PH slot. No space – and no possibility to stop the metal particles in falling in the inside of the lens.

After another 20 minutes the screw was away, and the inside of the lens full of debris. But I could separate the barrel.

Another surprize: under this other 3 screws were glued too. Hrrrrr.

 

The broken screw, the drilled screw and the normal thread.

As next I had to eliminate the debris. At first I tried it from the front. It’s  huge front lens – and no visible method for disassembling.

I tried to rotate the inner ring in the front of the front lens – but was stuck.

And then came the secret weapon: a little bit of alcohol (in my case methanol) between the internal and external thread (has a pitch of 0,75mm).

This helps always. (You can use it by stuck filters for example – and any liquid could work, vodka or whiskey, whatever). The ring came out, the front lens came out – but no further possibility. At this moment I had to clean the lens, and to put it back.

In such cases with big and heavy  lenses I always use my home-made suction tool.

  

To eliminate the broken screws I use my brand new small (Chinese) milling machine. At first milling the screw with a tungsten-carbide end milling cutter, after that making a centre of the drilling, then the drilling itself. A spiral drill bit would never stay in the middle of a M2,5 screw, without a centering bore.

     https://youtu.be/vPoilxqQODk

  After this I drilled the holes 15 mm deep – and I cutted ca. 12 mm long thread instead of the original 6-7 mm.

In the meantime I cleaned the lens internally and externally, mounted together the parts. The “dirty” lens element has not been cleaned as it should be – but even after cleaning with white spirit, alcohol, methanol etc., etc. remained on it a bigger spot, which was visible only after  breathing on the glass.

Here are the screws which I user (with Torx-slot,to be able to take them out later), and the mounted barrel. By the way: I always lock important screws. But always with a material which makes possible the disassembly later. Like Loctite 243 for example.

(“LOCTITE® 243™ is designed for the locking and sealing of threaded fasteners which require normal disassembly with standard hand tools. The product cures when confined in the absence of air between close fitting metal surfaces and prevents loosening and leakage from shock and vibration”)

 

After assembling, cleaning etc the lens, I went on the internet, just to see, approximately how much is the value of that lens.

 

My dear god…. Approx 3000 euros.

 

I have never drilled a hole in a piece of metal with that value. Great feeling!

7d flash overexposure – RTFM, RTFM, and again: RTFM

I repaired a 7d for somebody (a faulty rotary switch, and a general internal cleaning, with glueing the flying screw, which was of course on the side of the shutter motor), and after assembling it I checked the general functions of the camera.

And I have found, that the flash makes always overexposed photos, and there is no preflash possible (you know, that one which you can trigger with the “*” button. OK, I disassembled it again. No sign of any damage or fault. Assembled again – no preflash. Hrrrrrrr.

As the camera has been purchased recently as a used one, I was on the limit to give it back to the owner, mentioning that the camera has this small deficiency – but then i started to go through the menu – and i have found of course,that on these cameras there is possible to set E-TTL or manual flash, with different flash intensities, etc. Ouups. OK, I made the basic setup – and the flash was ok again…. 

 

The relevant information from user manual of the 7d

 

But what about the 40d?

The 40d has the same Menu item – but is greyed out!

So on the 40d it is not possible to set up the flash. Just on or off. 

 

Note: RTFM means https://en.wikipedia.org/wiki/RTFM