No Extruder heating caused by failed AD8495 Thermocouple amplifier

Hello Zortrax,

Recently received a unit from a customer that would not heat, they had already purchased replacement heater/thermocouple and several extruder interconnect cables, but the issue persisted.

Symptom: Extruder will not heat.

When executing "heat extruder" command, the display immediately switches to "done heating", with no noticeable heat on the hotend.

For testing, we unplugged the extruder cable and confirmed that an error #302 appeared, we then bypassed only the thermocouple amplifier output leaving all other connections intact to allow the machine to initialize.

Once initialized with no errors, we executed "heat extruder" and fed a voltage ranging from .8v to 1.3v to the sense pin on the micro, at this point the display properly registered heating, proving that the mainboard is ok, and the chip is questionable. See video.

When measuring the chip out of circuit, it fails passing 1.3v which with the math from the datasheet means it *thinks* it sees a temp of 260deg C, which just so happens to be around the appropriate temperature for ABS, which is why the machine happily thinks the hotend is at temperature with the chip fails, but detects no problem condition.

I believe the machine is out of warranty, so I will be sourcing a replacement chip from mouser/digikey and replacing it directly on the extruder PCB.

Hello Zortrax,

Recently received a unit from a customer that would not heat, they had already purchased replacement heater/thermocouple and several extruder interconnect cables, but the issue persisted.

Symptom: Extruder will not heat.

When executing "heat extruder" command, the display immediately switches to "done heating", with no noticeable heat on the hotend.

For testing, we unplugged the extruder cable and confirmed that an error #302 appeared, we then bypassed only the thermocouple amplifier output leaving all other connections intact to allow the machine to initialize.

Once initialized with no errors, we executed "heat extruder" and fed a voltage ranging from .8v to 1.3v to the sense pin on the micro, at this point the display properly registered heating, proving that the mainboard is ok, and the chip is questionable. See video.

When measuring the chip out of circuit, it fails passing 1.3v which with the math from the datasheet means it *thinks* it sees a temp of 260deg C, which just so happens to be around the appropriate temperature for ABS, which is why the machine happily thinks the hotend is at temperature with the chip fails, but detects no problem condition.

I believe the machine is out of warranty, so I will be sourcing a replacement chip from mouser/digikey and replacing it directly on the extruder PCB.

Yeah, there is a silicon chip on the extruder PCB whis is responsible for amplifying the voltage. If the replacement of heater&thermocoupler did not help, I would replace the whole extruder PCB.

Let us know if it solves the problem.

Is the extruder PCB available as a stock item?

I did not see it in the store, the machine is out of warranty so I can’t expect much assistance or timely response from support without a proof of purchase.

The chip is already ordered, I’ll have it Wednesday to hopefully confirm resolution of the problem.

4934

IMG_4955.jpg

Good news, replacing the thermocouple amplifier has resolved the heating issue and the machine is now printing again.

That should wrap this thread, would be great if the extruder PCB was available in the store.