Canon Pixma MP640 - won’t turn on

PeterBJ

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With a DMM, some electronics knowledge and some DIY test cables you can test the PSU. See this thread and also this post for the adapter cable. The operating voltages for this PSU are 24 and 32 VDC. The standby voltages are lower. Here is the pinout from an extended service manual for the MP640:

MP640 PSU.jpg


This is the pinout for the power connector, on the PSU pin 1 is a control input, pin 2 and 4 are grounds, pin 3 is +24 V out and pin 5 is +32 V out.

The pins are small and closely spaced so the use of an adapter cable is strongly recommended for testing as a short circuit could ruin the PSU.
 

PeterBJ

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I have a working MP640 and as the PSU is easily removed by loosening two clips so I tested the voltages in standby and operate mode. The test cables can be made from control LEDs and reset switches from old computers as in this thread. Ignore the smaller connectors in this post, they don't fit this PSU.

The pin 1 control input is the top pin in the connector. Ground pins 2 and 4 are internally connected. Without control voltage on pin 1 the PSU is supplying the lower standby voltages when connected to the mains. I measured +8.3 VDC on pin 3 with pin 4 as ground and +11.0 VDC on pin 5 with pin 4 as ground. With +3 VDC on pin 1 with pin 2 as ground you get the higher operating voltages. I measured +24VDC on pin 3 and +32 VDC on pin 5, both with pin 4 as ground.

I got the 3 V control voltage from two alkaline AA cells in a battery box.

The specs on my multimeter is +/- 0.5% +/- 1 on last digit. I used the +200 VDC range for all measurements. If your PSU gives the same voltages +/- a few tenths of a Volt it is OK.
 
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