Replacing the main chip

  • One year back I was using DUET Wifi. Due to wrong PLA fan wiring, it got short circuit. Due to other works I forget that.

    Now I thought of repairing it. Any possibility of changing only the main chip?

    I hope the facility may be available with DUET3d itself. If I ship the board, is it possible to get it replaced and ship back to us. I am at Hyderabad, India.

    Now when connecting to board, all endstop LEDs are glowing.

    Please find the attached images for references.![alt text](WhatsApp Image 2019-10-04 at 5.37.51 PM.jpeg WhatsApp Image 2019-10-04 at 5.37.51 PM (1).jpeg WhatsApp Image 2019-10-04 at 5.37.51 PM (2).jpeg image url)

  • FYI, I’ve attempted to swap out the processor before on a board where the chip was damaged (failed to burn the firmware), and I failed pretty epically despite having a hot-air gun and the proper tools. The feet are so fine pitch it makes it difficult to get everything lined up properly.

    Also, with the lights stuck on, I’d be worried about a blown regulator or something as well. Might be a more intensive repair. But of course, I’ll defer to the duet3 team.

  • administrators

    @selva_tvi it does look like the main processor, at least, is damaged at first glance. one of the issues is if that has been blown, by excessive voltage on the 3.3V rail then there is decent probability that the other 3.3V supplied ICs such as the stepper drivers have also been damaged. that would make the board un economical to repair, especially if you were to ship it from India to our repairer and then ship back again.

    If you want to give it a go, the most economical option may be to source the processor locally and see if a local mobile phone or other electronics repair shop will swap it for you.

  • administrators

    The first 2 times I tried to replace a blown CPU, I failed because of PCB traces lifting. The next 2 times, I succeeded. My rules for success:

    • Use a proper hot air station with a square output nozzle
    • Put the board on a hot plate and heat it to 120C. This is pretty much essential when replacing stepper drivers, voltage regulators and other chips that are heatsinked to the PCB. Probably not essential when replacing a CPU, but it means less heat is needed.
    • To remove and place a large chip such as the main processor, a vacuum pickup tool is essential. Manual ones can be purchased very cheaply on eBay, although they tend to leak. I've now bought a small 12V vacuum pump to use with the pickup tool.
    • The hot air will loosen other components around the processor, so be very careful not to touch them or jog the board
    • Use a no-clean flux pen to put flux on the processor pins and the pads before putting the new chip in place
    • Ensure that the new chip is lined up perfectly before applying hot air to solder it
    • After soldering, check with a magnifier for unsoldered pins (fix with a fine-tipped soldering iron) and then for solder bridges (remove using solder wick).

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