Canon printer - no power up

Discussion in 'General Electronics Chat' started by ozzie_fred, Jun 21, 2013.

  1. ozzie_fred

    Thread Starter New Member

    Jun 21, 2013
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    I'm having a problem with a Canon PIXMA iP4000 printer not powering up. It had been working perfectly but has refused to power up.
    I have the power supply out and the primary side of the switch mode PS is fine and the two output feeds are 8 and 10 volts. I have read elsewhere that pin 5 of the output connector brings back a low voltage (3volt?) that tells the PS to increase these outputs to the rated 24 and 27v.
    I haven’t traced this sense circuit yet but presume that it is not supplying the required “bias”.
    Can anybody help with any experience as to common problems with this sense wire’s circuit, or where I can get a schematic?
    (BTW the power board has 2 numbers on it, PS-A126 and P1222)
     
  2. ozzie_fred

    Thread Starter New Member

    Jun 21, 2013
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    Following on advice gleaned from another site, I have disconnected the printer from the PSU and put a dummy load of about 20% of the supply's rating and applied an externally sourced 3 volt to the sense wire (pin5) of the PSU output and the PSU then increased its outputs into the dummy loads to 28 and 24.3 volt. So the PSU is OK.
    It's a bit of a crummy design that shuts the system down to such an extent that it can't even report its problem!
    I am tempted to apply the 3v to pin 5 with the PSU connected to the printer to see if I can at least get the error codes and address the underlying problem. Any thoughts on the wisdom of doing this? I'd probably play safe and cut the circuit to inject the 3v (or could I just connect it onto this circuit through something like a 1k resistor?)
     
  3. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    look for a switch that is activated when the printer head carriage is located in its 'home' position. This may be what is keeping you unit from working. If this switch does not change states the unit thinks the motor is locked up and will not supply voltage to it.
     
  4. ozzie_fred

    Thread Starter New Member

    Jun 21, 2013
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    Thanks Kermit2. I couldn't find such a switch, but looking in that area, I decided to take the print head out and found that it had suffered a rather severe burn. Reconnecting power with the head out gave a normal power up (and an error code that means print head problem (an understatement)).

    I see that replacement print heads are available (not cheap) and one site that has refurbished ones warns that new ones can burn out immediately if the main board is faulty and they warn customers to check their main board.
    1. I wonder if anybody knows how such a check could be done?
    2. I also wonder if a new one may burn out if it is used before the ink had had a chance to get into the new head, allowing it to overheat because it was still dry?
    3. Has anybody on this forum had the experience of a replacement head burning out immediately?
     
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