Broken digital camera short circuit problem

Discussion in 'General Electronics Chat' started by hazim, Jul 20, 2010.

  1. hazim

    Thread Starter Active Member

    Jan 3, 2008
    419
    13
    Hi all,
    I have a Canon digital camera to fix. The camera stopped working, it totally doesn't turn on. I opened it and found an unattached screw under the screen and on an SMT board. I then said that it had made shorts on the circuit board. I think that transistors around the screw should be first tested. According to their codes I found that they are BJTs (only 3 ones on the screw side). I tested them on board since they are very tiny to my iron to detach... My DM give readings around 250 instead of something around 700 (PN diode testing..)
    Other that that, nothing looks to damaged on the board.
    Any help would be greatly appreciated.

    Regards,
    Hazim
     
  2. tom66

    Senior Member

    May 9, 2009
    2,613
    214
    Does your meter have a transistor test (H_{fe} mode)?

    Can you give us the part numbers for these transistors? It could be that they are difficult to get hold of, but you could substitute them for equivalents.

    I would also ask, do these manage power or do they do something else? If they don't do power management, then it is unlikely that they are the problem. It is quite likely they manage power if they are near the batteries or a DC input socket.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    If you're getting 250mV in diode test mode, sounds to me like you could have BE or BC shorts. You should be getting around 600mV-700mV or so.
     
  4. hazim

    Thread Starter Active Member

    Jan 3, 2008
    419
    13
    3D, H2 (BC557B) and 6B (BC337). There are more but far from the area were the short accrued or the voltage source. Also I found one part with code "2.3" connected like a fuse directly after the +ve terminal communig from the battery, there are similar parts on the board (2.3 also and 1.2) they are connecting but the first is open, I replaced it with a 1Ω SMD resistor but the camera didn't worked, I shorted it.. the same.
    I can't know if the resistors manage power or what, it's a complicated SMD double face board, but I know that the short due to the screw was near them. I'll check the camera later and look to your suggestions and try to find some replacements for the transistors.

    Yes I think the same.. Also there are packages of two transistors were the reading from one transistor is about 700 while the other is about 400 :confused:
     
  5. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    what camera model are you working on?

    There are typically 3 or more fuses coming off the power board. You should use a replacement fuse, even if it's hard wired off board, to avoid further damaging circuitry.

    These cameras require certain switches to be made before they'll power up. The battery door and the memory card switches are two of them. The keypad subsection must be plugged. On the 510/20's, you should be able to power up without the flash subsection and without the LCD plugged in.
     
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  6. hazim

    Thread Starter Active Member

    Jan 3, 2008
    419
    13
    It is Canon PC1225. Yes I found 3 SMD fuses, the fuse directly after the positive voltage coming to the board is open, I can't find a similar one for now, I first used a 1Ω resistor but the camera didn't worked, I shorted this 1Ω resistor and also it didn't worked.
    If it's required to make certain switches can you please give me a link or explain tell me which switches and what to do with them?
     
  7. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    I know of no links that can help, although there are many that play around with camera assembly / dissassembly. With the cost of such cameras, in non working order off of Ebay, it wouldn't hurt to have a couple of the same model, to explore thier operations.

    I use these cameras for the game cam scene, and have probably 40 of the 510/520s, which I like for the fact that they can be controlled via USB. There are a couple of typical problems that these units run into, and are repairable for the most part.
     
  8. hazim

    Thread Starter Active Member

    Jan 3, 2008
    419
    13

    Ok but you said that these cameras require certain switches to be made before they'll power up. What are these switches? and do you mean there is a specific switchs combination to power it for the first time after repairing:confused:??
     
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