Geeetech

I have an i3 pro B with GT2560 Rev A+
The problem started while I was changing the nozzle, I figured I could also remove the hotend and clean it. So I removed the screws holding thermistor and heating element in the aluminium block, took them out, cleaned it. When I put it all back together, I noticed "err: MINTEMP" error on the LCD, temperatures being "0/0" for the extruder and "room temp/0" for the bed.
What I have tried so far:
1) I followed the advice given here viewtopic.php?f=13&t=17030 , when pins are shorted, it shows 358/0 on both bed and extruder, so I figured the board is fine.
2) I plugged the extruders thermistor in beds thermistor socket, and it works. Plugging the beds thermistor in extruders socket, does not work, so it somehow must be the board. Both thermistors are OK, room temperature resistance is around 100K, drops when heated.
3) I tried inspecting the board closely, cant see any obvious damage. See the picture here https://drive.google.com/open?id=10zJ-S ... NDTWbhHZa0
4) I found this thread https://www.thingiverse.com/groups/prus ... opic:21620 , and figured I'll try switching TEMP_0_PIN with TEMP_1_PIN in marlin, and plugging the thermistor in T_HE 2 socket (unused one) and updating the firmware. This, to my surprise, also did not work - it shows 277/0 or 228/0 for the extruders thermistor, so there is no MINTEMP or MAXTEMP error, as far as I could tell, everything else (steppers, heaters, LCD etc.) works fine.
5) I checked the schematic for the board https://drive.google.com/open?id=1Glg0R ... yMsJmUvNxf and measured the three resistors R4, R21, R23 they should all be 4,7K, but the middle one is around 400 ohm. The other two are 4,7K. There is continuity between grounds, and between pins 87 88 and 89 on Atmega chip (Analog inputs 8 9 and 10) and the respective sockets.

Does anyone have any suggestions? Whats wrong with the middle resistor? could the SMD caps have blown? Are the Atmega2560 pins blown?

I don't want to buy a new board, so any help would be much appreciated! Thanks!

I have a similar problem with i3 pro
With temp sensors DISCONNECTED, LCD display shows extruder 234 degrees Celsius and bed 21 degrees Celsius
It just suddenly went that way and can no longer print!!?

S

marklinoz wrote: Mon Dec 17, 2018 9:50 am I have a similar problem with i3 pro
With temp sensors DISCONNECTED, LCD display shows extruder 234 degrees Celsius and bed 21 degrees Celsius
It just suddenly went that way and can no longer print!!?

Same problem as marklinoz

my sensor that doesnt work is the extruder 1 in my prusa ipro b..Its stuck on 157 even with the termistor disconnected

I have to say that ive changed extruder with a clone e3d v6...
The bed sensor is going perfectly.

Does anyone have an answer???

My solution after having fried the A9 (T0) input of the micro-controller.
From memory:
I modified my heat block and after reassembling everything the temp was stuck on 93C cold. with everything disconnected or only the daughter board connected the temp should be -14C. (if I remember correctly)
After researching online i found that the cause was one of the leads or more of the temp sensor coming in contact with the heat block and the heat block being energized from the cartridge's leads. Maybe from cranking too much on the screw holding the sensor or having the glass of the sensor breaking and so on.

My solution was to isolate the heat block with silicon tape i had laying around (rated for 280C).
- the side with the leads of the heating element (cartridge) should protrude 1 mm off the heat block.
- Make 2 pin holes in the tape so the leads can go trough.
- Go around the heat block one time with the tape. The tape only glues to itself.
- Make another pin hole in the tape so only the glass of the temp sensor can come in contact with the heat block. I don't use the original holding method for the sensor anymore.
- Tape again one time around the heat block to retain the sensor in place.
- Check the continuity between the heat block and the 4 leads before reconnecting the leads to the board, there should be none. (assumption)
- Change the white wire (temp sensor) from one molex (T0) to the other (T1).
- In the Arduino software open the pin file for the board and go to the section "temperature sensors" change TEMP_0_PIN 9 to 11(switch the two or whatever) then upload the firmware.
- reconnect everything.