16 tháng 4, 2010

Cách tháo máy canon a550

I bought a two month old Canon A560 camera from ebay with a broken battery door, and broken tabs which hold the door down. After registering the camera, Canon customer's support gave me the phone number of Canon's parts sales department. I was really surprised how cheap the parts were (almost half the price of OEM parts). Canon customer support were really helpful, and from my explanation, suggested that I needed to replace the front of the plastic outer casing, the battery box, and the battery door. Including shipping, that was coming to $40. However, they said that they will not be able to give me repair/ service manual.

Further research indicated that there wasn't much difference between A550 and A560 body parts. From different photographs that I saw on internet, I figured that apart from the LCD, there wasn't much difference, at least from the outside. So I took the chance, and bought a broken A550 from ebay for $20, including shipping.

I did the project quite late at night, so couldn't be bothered to use a tripod to reduce camera shake. Some of the photographs are a little blurry. However, you should get the general idea of how to open the camera.

The following picture shows the A550 camera how I got it from ebay. From the seller's explanation, and the physical appearance, it seemed that the lens assembly was damaged:
NOTE 1: Be very very careful. The camera has components (for flash) which store high voltage. If you're not careful, the shock that you might get is not powerful enough to kill you, but definitely remember it for a long time. Despite being warned by many people on the internet, I got the shock anyway, but I thought that I'll still warn you anyway. My writing these notes is proof enough that it's not strong enough to kill you.
NOTE 2: I took these photographs just as sort of breadcrumbs to guide me back in assembling the camera if needed. I have tried to capture every detail, but if I've missed something, I'm quite sure that these notes give you enough information that you'll figure out what to do in order to take it apart.
My aim was to salvage the battery box, the front plastic casing, and the battery door. The battery door was hinged in the battery box, so I figured I need not disassemble it.
Even though I just needed the battery box, I decided to dis-assemble it completely to see how it's been put together.
First of all, you need to open the camera. For this, you have to unscrew the screws on the outer body. I took the bottom screws out first:
Next, the screws on the sides come off:
 The screw on the other side:
This is the tool that is recommended to open the equipment (being plastic, won't harm the plastic body), but I seldom use it:
 Once having removed the screws, you need to take the front and  back cover off. The battery box is a good starting point. Force the front and the back cover apart by applying force in the direction shown. You won't be able to open it using your forefinger and thumb, as shown in the pic. This is just for illustration. I held the camera, and applied (restricted) force by both thumbs, and forced it open:
I say restricted, because I just opened it until the latches holding it let go. Then, using a screwdriver, I wedged the other side open. You might have to use some "persuasion" for it to open up :-) Don't be afraid to use some force when it is required. What do you have to loose? It's already broken
Still, don't force it open all the way. Here's how much you should open it once the latches holding the two halves let go:
Using only slightest force on the top of the camera will make the front of the camera come off. Be careful in putting it back on, though. The part indicated by the arrow consists of a very thin copper plate. It can easily bend (happened to me), and will cause the zoom button stop working. You will then have to straighten it again.
Next step is to take the back plastic case off. You can start on the end shown. Put the screwdriver (small one) in as shown, and wedge it open as indicated below. Also note that the camera strap will have to be taken off. Otherwise, the back cover won't come off.
Again, don't open it all the way, because the camera mode select button will still be held to the main body by a cable ribbon. See the hole indicated by the arrow? Put a needle in the hold, and pull the cable ribbon away from the camera to dislodge it. 
And the back cover comes off:
Next, I wanted to take the main ribbon cable assembly off. For this, I had to remove the shield holding it down. The top of the shield is held down by the screw indicated here. Once the shield is off (not shown here), I had to pry the cable open with a watch screwdriver. The cable was being held down on the battery box with several plastic tabs. Slightly prying the cable (as being shown) will make the cable come off. 
Part of the shield is being covered by the buttons PCB (left side in the pic below). To remove it, the LCD had to be taken off (secured with two screws indicated below): 
The LCD will still not come off, since it is attached to the main PCB via a ribbon cable. Prying open the flap (indicated with the arrow) will make the ribbon cable come off with a slight pull.
Next, unsrew the two screws shown encircled, and then after that, the only screw securing the shield will be the one indicated with an arrow.
The shield will come off as shown below. Next, you'll have to open the flap shown to dislodge the buttons PCB being held to the main ribbon cable assembly (indicated with arrow in the pic):
Next, you need to take the two screws at the bottom:
To take off the main ribbon cable assembly now, pry it by inserting watch screw driver under it in the places indicated. You'll also have to pry the LED (rightmost arrow). The arrow shown in below indicates that here, the ribbon cable might be secured down with a bit of glue. The ribbon cable won't be damaged if you put a screwdriver under the cable assembly, and slightly push it up to dislodge it.
Next, you need to unscrew the screw shown on the left side. This is the last screw you have to remove in order to take the battery box off, but since it was more of an exploratory mission, I took the screw on the right side off too. This secures the lens assembly to the main body.
As I said, you need not have take the screw on the right side off. The only two screws that were left that need to be taken off to remove the battery box are indicated in the pic below (already removed here):
Next, flip up the flap indicated below to remove the ribbon cable. The portion of the ribbon cable assembly which has two LED's will be held on to the body with plastic tabs, and you can slightly push under it with a screw driver to dislodge it: 
The following photo is overexposed (forgot to turn the flash off), but shows me flipping the latch open on the socket:
And off comes the ribbon cable assembly:
You'll have to remove the screw (not indicated here, but shown removed on the top left corner, just below the flash bulb. The plastic cover of the flash has been removed too). You can just pry open the top which has the flash and the viewfinder assembly:
In order to remove the lens assembly (not done now, but later), you'll have to push it here to dislodge it:
Even when the battery box comes off, you'll have to desolder the two wires indicated in the picture below. This is supplying the main circuit board power from the CR1220 battery.
Next, you'll have to desolder the main battery wire terminals (indicated below). You have an option to either do that, or completely remove the main circuit board, and then desolder the wires from there. But I preferred not to do that, because I didn't want to open the other camera all the way. 
The picture blow shows the battery box held to the rest of the camera through these wires only:
Remove the tape first:  
Then desolder the wires:
This is enough to take the battery box off, but I went ahead to disassemble the rest of the camera. The following picture shows where I desoldered the CR1220 battery wires:
The battery box, which I really needed. You can see the wires, which go through a hole in the battery box to the terminals. These had to be pulled slightly to take them out. They were being held behind the plastic tab (shown with yellow arrow). This is quite clear in a picture above where the camera is still hanging on to the main board through these wires.
Next, the plastic piece on the other side can be taken off with a little "persuasion".
In order to take the main circuit board off, you need to remove the screws shown encircled, and flip the catch holding the ribbon wire (indicated with red arrow):
At the back, it's held to the lens assembly with another cable. Flip the catch on the socket as indicated to make it loose, and then pull the ribbon cable out:
So off comes the lens assembly. This assembly is the biggest problem with digital cameras. Even though the picture is not clear, you can notice the sand particles on the lens assembly. If you're not careful and go to the beach with the camera, and drop it in sand, this is what will happen. And if you try to repair it yourself by knocking it, as indicated in some places on internet, look at the first picture of what could happen :-) Knocking it might dislodge some sand particles that might be clogging the gears, but it won't correct the problem. The particles will still be there, and will again clog the wheels later on. Opening up the lens assembly is a separate project.
Ok, now to the other camera. The damage to the camera has been indicated. The two out of three tabs which hold it down were broken. the third tab was intact, but the part of the battery door which holds on to this tab was broken.
Opening up the camera in the same way as A550 was opened revealed that the front is almost exactly the same, but there were differences on the back side. The LCD screen is larger on this guy, and is held to the main board through not just the ribbon cable, but also a couple of wires (red and black, most probably supply power to the LCD backlight). The additional bracket to hold the LCD is also shown. The screws that I needed to take out, and the two wires connecting the CR1220 battery to the main board are also shown. 
From the front, I needed to take the screws off, and desolder the wires connected to battery terminals after removing the tape: 
After removing the shield, took off the ribbon cable assembly. The battery box was removed carefully, and replaced with the one from other camera (the operation not shown here, since it was simple). A couple of things to note. It wasn't easy to put the battery wires back through the hole. Second, the piezo-electic buzzer caused some problems while putting the battery box back in place. Since I didn't take the main body bracket out, I had to bend it slightly to take the battery box out. Didn't have to do it so much as to bend it permanently, though. Other than that, it was simple.
Here's another tip. I put the screws on a white paper, and mark it where they came from. You can see the screws from the bottom, front, switch PCB, top, shield and casing. There were a couple of more screws from the LCD, but they were put on another paper, not shown here. This helps me not mixing the different sized screws, and I now seldom have any extra screws left over. I do the same sort of labeling for the parts that I've taken out.
Ok, here's the working camera. The front of the camera now shows it to be an A550, since I had to replace it (one of the tabs that was broken was on the front body casing). However, it doesn't impact any of it's operation, since except for the label, the front is exactly the same.
Update: I've received a lot of emails asking for a particular cable. In the initial instructions of taking the camera apart and putting it together, I'd missed out information about it. I'm now including pictures on where it goes:
The LCD ribbon cable has not been disconnected.
With the LCD ribbon cable removed, it can be clearly seen how the cable is connected.
This screw holds the copper tab. Once it is removed, the cable can be taken out.
The removed cable. Follow the reverse process to put the cable in place.

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