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FF Finder thermocouple replacement

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    FF Finder thermocouple replacement

    Hi Everybody.

    I accidentally tore the leads out of my thermocouple and so I ordered a new one. They sent the wrong one first (M4 thread, wrong connector), but quickly sent the right one after I asked.

    When I say right, I mean, the M3 threaded end and header connector fit properly, but the thing looks different other than that. (it has blue heatshrink down the cable length, where my old one just had two black wires.)

    When I attach the replacement and start a filament load, the temp immediately reads 286-287 deg c. Jiggling cables doesn't help. Using jumper wires to see if the sensor is wired wrong polarity, it still reads 286-287 ambient. When I use jumpers to connect the incorrect sensor I received previously, it also reads 286-287.

    Is it maybe that my Finder is old and has a different sensor type? My serial number is FFF205343, Firmware v2.0.21.285 F2.3 20180701.

    Thanks,
    Craig

    #2
    A thermo couple device is polarity sensitive, try connecting the wires the opposite way round.
    The FF Dreamer & Finder use a K-Type thermo couple. the wires are made of specific dissimilar materials that generate a voltage when heated. The Mother-Board detects this volttage change & works out the temperature.
    All thermo-couples are polarity sensitive, & iff connected the wrong way round they will give some very odd readings indeed.
    Note also that there are many types of thermocouple that each react to different temperature ranges.

    Failing that, if you still have the original thermocouple with the little brass M3 nut collar thing.... you will notice the brass collar is slightly crimped/miss-shapen where the wires go in.
    Use a pair of pliers or vice-grips & gently squeeze it back in to an approximate circle again....then... use a 2mm drill bit & drill out the debris in the hole where the wires originally went.... the depth is approx 4 to 5 mm.
    From the original thermocouple wires, strip about 8mm of insulation off both, tightly twist together & carefully fold on itself 3 times in 3rds, insert this bundle of wire into drilled hole of the brass collett & re-crimp without chopping the wires but a tight slop free grip on the folded wire bundle.
    Re-fit & it will work forever....

    Note ALL the latest FlashForge Thermocouples have Blue heat-shrink over the wires now.

    Alternatively PM me, post me the original collett & wire remains with a pre-paid return envelope, & I will fit new thermocouple wires in it for you & return.
    Regards
    Grant B

    Comment


      #3
      Thanks Grant.

      It turns out, even though my Finder was bought recently (Flashforge store on Amazon), it is an old model and actually has a NTC thermistor instead of a thermocouple! Flashforge USA knows nothing about this, and I didn't have much luck with the Chinese contact either. The only two replacement parts to be ordered from them are both thermocouples-- in either M3 or M4 thread.

      I can't imagine this thing being a knockoff because it is a complec machine with a lot of styling, and it looks exactly like all the pictures and accepts Flashforge's firmware and printing application.

      I looked on Aliexpress and found a generic M3 thermistor that looks identical to my old one, then found a local seller of it on ebay for faster shipping. It ended up working fine.

      If anyone else is in this same boat, heres the aliexpress listing and then an American supplier.

      https://www.aliexpress.com/item/Funs...812587287.html
      https://www.amazon.com/Gulfcoast-Rob.../dp/B07B3ZYBTM

      Cheers,
      Craig


      Comment


        #4
        Hi Craig
        You gave me the clue I needed to repair my Finder which has been broken since last December. I damaged the temperature sensor while performing a hot end upgrade. My Finder must have been made even before yours because its serial is FFF199471, though it was bought as new in August 2018 from a reputable Australian hobby electronics retailer.
        Oddly, the damaged temp sensor looked exactly like the Thermocouple currently sold as a Finder spare part by Flashforge with blue cable sheath and black heatshrink. However, a replacement blue thermocouple sensor bought from Flashforge produced the exact symptoms you describe. LCD said temp is 288degC while hot end remained stone cold.

        After finding this discussion, I ordered the thermistor from your aliexpress link and my Finder now works normally even though the thermistor looks nothing like the Finder replacement part illustrated on multiple online spare part websites.

        The unfortunate bit is that I have also replaced the print head ribbon cable, the heater cartridge, the extruder PCB and the entire motherboard at great expense without solving the problem when it only needed a $7 thermistor. Oh well, my Finder now has an extensive set of replacement parts on hand and should function as my back-up printer into the distant future.

        Cheers'
        Peter
        NOTE: An earlier version of this post has been held up in moderation as suspected spam. Can't think what was spammy about it so nobody be confused if it ever reappears here. I thought it important to confrim that Craig's advice works.

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