Trouble with DUET 0.8.5. died?

avaradus

Hello All !

My duet worked fine for a long time.
But recently something has trouble in electronics and now the temperatures are not right.
CPU temp show -274.9 degrees and heater and bed show wrong temps.
Tried to disconnect everything from the board, powered by USB and nothing changes.

dc42

That sounds like an issue with the ADC. Shorts between the thermistor and heater wiring can cause that on the Duet 085. Also check whether component L7 looks intact - it's a small black component close to the processor.

avaradus

@dc42 said in Trouble with DUET 0.8.5. died?:

That sounds like an issue with the ADC. Shorts between the thermistor and heater wiring can cause that on the Duet 085. Also check whether component L7 looks intact - it's a small black component close to the processor.

L7 looks like ok, but i check it with multimeter and it shows 20 ohm. it's wrong ?

dc42

It should be less than 1 ohm. Check what your multimeter reads when you short the leads together.

avaradus

@dc42

@avaradus said in Trouble with DUET 0.8.5. died?:

@dc42 said in Trouble with DUET 0.8.5. died?:

That sounds like an issue with the ADC. Shorts between the thermistor and heater wiring can cause that on the Duet 085. Also check whether component L7 looks intact - it's a small black component close to the processor.

L7 looks like ok, but i check it with multimeter and it shows 20 ohm. it's wrong ?

@dc42 said in Trouble with DUET 0.8.5. died?:

It should be less than 1 ohm. Check what your multimeter reads when you short the leads together.

Wires of multimeter has 2 ohm and with L7 shows 22 ohm.
And if i short E0 temp duet then shows 3090 degrees
If short bed temp then duet shows 7841 degrees
May be processor is overheat ? it's very hot !

dc42

It sounds to me that the processor has been damaged. The symptoms you describe (overheating processor and L7 failed) suggest there was a short between the VSSA side of a thermistor connection, and a heater or fan wire. I've heard of this happening a number of times on Duet 06 and 085 boards. That's why we added protection to the VSSA line on the Duet WiFi/Ethernet.