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  1. #1

    Qidi X-Smart Not Reading Hotend Thermocouple Temperature - Please Help


    I have a Qidi X-Smart printer. It is not reading the temperature of the thermocouple on the hotend, or, rather, the software shows a temperature of 600+ degrees (fahrenheit) whether the thermocouple is connected or not.

    Remedies I have tried so far:

    1) Replace the theremocouple (first with a generic one from Amazon, then with an OEM replacement from Qidi). Result: No change
    2) Replace the breakout PCB board to which the thermocouple connects. Result: No change
    3) Re-seat the thermocouple in the hot end. Result: No change
    4) Replace the ribbon cable that connects the breakout PCB to the main board. Result: No change
    5) Software "factory reset". Result: No change

    Prior to experiencing this problem I had a blockage of filament in the hot end. Once I remedied that the current problem started.

    I took the printer to the local 3d printer repair shop. After a month they hadn't come up with a solution or even a diagnosis, so I took the printer back and tried replacing the parts listed above. I would think if the problem was something obvious, they would have figured it out quickly.

    Any help or insight or hypothesis to be tested will be much appreciated.

    All the best.

  2. #2
    Sounds like the MAX6675 thermocouple amplifier chip is blown, probably from a short due to a frayed wire on the old thermocouple. I went through this very recently. I replaced the 8pin chip and was back up and running. If you are up for replacing surface mount chips I can show you what to do and where to get another chip cheap.

  3. #3
    Wow, thanks!

    Yes, I would be so grateful for any direction you can give me for replacing the chip you mentioned. I have no experience with replacing surface-mount parts, but definitely I am up for giving it a shot.

    I am not sure whether the best way to communicate about this is here on the forum. I will see if I can direct-message you.


  4. #4
    So if everything else on the printer seems to work there's a very good chance that this chip is smoked:

    ScreenShot 1276 Aug. 17 16.33.jpg

    You can buy the chips on aliexpress for $3 or so, from digikey for $20 or so, but best fastest option is to buy a breakout board that uses this chip on amazon or ebay for maybe $10 and swap the chip.

    This is pretty simple to do but you do need at least a good soldering iron. Good flux like chipquick really helps too.

  5. #5
    There are probably some good youtube videos showing the technique for replacing chips. Maybe practice with some scrap electronics.

  6. #6
    On my printer I didnt even need to take the pcb off the chassis which was nice. Just make sure to uplug.

  7. #7
    (Whoops - i deleted the Private message by mistake. But better to keep the information here so other people might find it.)

  8. #8
    Awesome! Thanks for the information. I have purchased Chip Quick RA 891 Rosin Solder Flux and NOYITO MAX6675 Thermocouple Module from Amazon. They should arrive tomorrow, and I will give it a go.

    Here are links to those two items on Amazon.

    Thank you so much!

  9. #9
    Looks good. To remove a chip:1) Put some flux on the pins and then melt lots of solder across all the pins on both sides. The more the better. Try to make a little solder bubble that covers all the pins. But be quick and don't linger with the solder iron. Using the flux and having a hot clean iron tip make this much easier.2) Slide an xacto knife blade or similar under one end of the chip and apply very very light upward prying force while briefly touching the solder iron to the solder bubble on one side. You should feel the pins on that side break mostly free but they might still be in the solder bubble. That's ok. 3) Shift the iron to the other side and repeat.4) If the chip hasn't popped off yet, shift back to side 1. Heat and pry a little more. 5) Repeat till the chip pops off. Never pry hard or heat for long or you risk yanking the traces off the board, which sucks.

  10. #10
    To replace the chip: 1) Use tweezers to position the chip on the traces. make sure the orientation is the same as it was. 2) Dab some flux on all the pins. Tack down one pin with the iron.3) If the chip is positioned ok over the traces, apply the solder to each pin very briefly. The flux will make it flow nicely without much pressure or time.4) Clean flux with alcohol or acetone and a brush or qtip. Inspect each pin with a mag glass or microscope or loupe to make sure all are soldered and none are bridged.

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