Ultimaker 2 ER02 suddenly arrived and keeps coming back

[RichardF 0]

Starting yesterday, after 2.5 years of use, I started getting the ER02 Heated Bed error. I never had this before. The first time, last night, it was about 15 minutes into a print.

This morning I jiggled the wires on the heated bed and then tried heating the bed under the maintenance menu. It seemed OK so I tried again. After this it got about 20 minutes into the print and threw the same error.

Next attempt involved removing the heated bed and tightening the screws on the connector (though they did not seem loose). After this, and again checking the bed heating, I tried to print once more, but now it threw the ER02 while heating up.

Next I dismantled more of the machine and made measurements.

Measured at the circuit board TEMP3 showed 4.78 kohm, about the same as TEMP2 which had no connection. TEMP1, meanwhile, was showing about 104 ohms, as expected. Turning to the heated bed connector, I initially got 4.78 k when measuring across the screws themselves, while the solder pads were showing the expected 104 ohms (it's cold in our house: the heating system is being replaced).

These solder pads always showed the same, expected, resistance. The screws were more intermittent: sometimes 104, sometimes 4.78k (which I assume is the resistance on the PCB).

I removed the sensor wires from the connector and verified that the resistance at the connector is 104, both solder pads and screws, and at the PCB it's 4.78k.

Re-inserting the wires, and screwing them tight, I found that the resistance at the screws was consistently 104, and it was also 104 at the PCB.

With this I reassembled and started another print. This time it got about 45 minutes into the print and threw the error again.

I'm now at a loss to explain the root cause of this problem. If it's an intermittent connection, why was it good for 2.5 years and suddenly, after several tightenings, showing connection drop-outs? The PT100 seems good -- I always measure the expected value close to it. The problem seems to be around the heated bed connector, but I haven't been able to understand nor fix it.

cheers,

Richard