Hotend Issue After Replacement

[Matsubaa]

I just replaced my hotend on my A10, it's a straight-up replacement and not an upgrade.

Installing the new hardware and running a new PID tune, I find there's a hard stop at 120C. The hotend heats up fine until that point and then hits a hard stop.

What can/should I try before I give up and replace it again?

Thanks

[Jarda3d]

PID tune is really for those who really know what it is and how to use it. Put safe original firmware values and try again.

[William]

Hi, you can try to change the value of the PID to the original value.
If the temperature does not rise after 120°,
You can check if your hot end thermistor is fully connected.
Whether the heating block is loose or not, measure the thermistor at the hot end.

[Matsubaa]

Okay, my multimeter says the thermistor which should be 100k resistance is 26k so I've got a replacement on order.

Thank you

[Matsubaa]

I have exactly the same behavior with new hardware and all the connections having been rechecked.

It seems unlikely I got 2 bad parts in a row but I've got very few surviving theories.

[William]

Hi, You need to check if your hot end is fully connected.
Perhaps some places are loose and the temperature does not rise properly.

[Matsubaa]

I've replaced the whole thing, disconnected and reconnected everything twice and checked the continuity of each connection on the hotend through the extension board's connector.

At this point if something's wrong, I'm betting it's on the control board end of the cable and I don't know exactly how. Destroying only the temperature control is a pretty specific kind of damage.

[Jarda3d]

Really? Heater should have same potential level as GND voltage, thermistor powered via pullup resistor to +5V and thermistor is in pulldown. Yes, some young enthusiastic dumbs connect thermistor as pullup to +5V which possibly lead to burn out some DC/DC power circuity (these I was see at arduino community). But I was think that Geeetech are not young ingeneers.

[Matsubaa]

when the heater shorts to the thermistor it tends to blow out the board.

This one sounds like a winner. I was replacing the hotend because I broke the thermistor while trying to change out a nozzle, everything is gunked up and glued together with plastic remnants it can no longer reliably melt on its own. It *shouldn't* have shorted to the heater but with it breaking off and just being a loose end, I don't actually know what it might have touched momentarily.

Now I'm off to shop for replacement controllers I guess...

[Jarda3d]

Geeetech, please do redesign of thermistor connection to be between analog input and GND, not between +5V and input. It is very important to do this change for safety reasons too. It is unbelievable, that this basic design error of teen enthusiasts should be on the commercial product.