[Solved] Ender 3 v1.1.3 Atmega1284P: Hotend Smoking & Thermistor Issue - Voltage Regulator Problem?

Hello all,

I have a problem with the new Creality Ender 3 version 1.1.3 printer. After many struggles with leveling the curved table and reassembling the crooked frame at the factory, I managed to bring it to service.
Unfortunately, yesterday, during a quick print in PLA, the hotend started to smoke, after opening it, I saw a burnt cotton wool (?) With a kapton, a heating block flooded with PLA with a melted thermistor. It was not a problem because it can be quickly cleaned and replaced, but the fault was the fault of the controller and not the thermistor.
When turned off and on, it shows a temperature of 162 * even though the block is cold and the thermistor off, in this case it should indicate MINTEMP or MAXTEMP error. The motherboard voltage to the Hotend thermistor is 700mV, and to the table thermistor is 4.7V.
What could be causing the fault? Defective voltage regulator or Atmega 1284P?

In the photo I marked the hotend thermistor input

Marqee wrote:

during a quick print in PLA, the hotend started to smoke, after unscrewing it I saw burned cotton wool (?) along with a kapton,

Where?

Marqee wrote:

After turning off and on, it shows the temperature of 162 * although the block is cold

and

Marqee wrote:

in this case it should indicate MINTEMP or MAXTEMP error.

And what conclusion?
I already know what is damaged, but if you have taken so many measurements and you still don't know how do you want to fix it?

11111olo wrote:

Marqee wrote:

during a quick print in PLA, the hotend started to smoke, after unscrewing it I saw burned cotton wool (?) along with a kapton,

Where?

Marqee wrote:

After turning off and on, it shows the temperature of 162 * although the block is cold

and

Marqee wrote:

in this case it should indicate MINTEMP or MAXTEMP error.

And what conclusion?
I already know what is damaged, but if you have taken so many measurements and you still don't know how do you want to fix it?

Do you like making posts? Your answer added nothing to the topic except "I know but won't say".

You didn't even want to write that the software is MARLIN!
If disconnecting the thermistor does not change anything, the damage is on the board. I do not have a diagram of this crap but the thermistors are most likely made in the same way as in other crap plates of this type, such as RAMPS.
Compare, measure and maybe we can fix it.

11111olo wrote:

You didn't even want to write that the software is MARLIN!
If disconnecting the thermistor does not change anything, the damage is on the board. I do not have a diagram of this crap but the thermistors are most likely made in the same way as in other crap plates of this type, such as RAMPS.
Compare, measure and maybe we can fix it.

11111olo did not mention Marlin as Creality uses it but changed and it is from a proprietary source which people hold against them.
I checked the voltages on the other components and they are normal. In your opinion, Atmega's fault, or maybe any of the resistors fell and so lowers the voltage from 4.7V to 700mV?

I don't know what your concept of electronics is, but you don't really have one.
You will write right away that I do not want to help and it is quite the opposite.
Help is not pointing with a finger, but directing (guiding).

Something short circuit. I do not know how it is done on this board, but usually there is a 4k7 resistor connected to Vref and a 10uF capacitor in parallel to the thermistor.
If the second thermistor shows the temperature correctly and the pull-up resistor has the correct resistance and the capacitor is not short-circuited, it all indicates that the microcontroller is damaged.

If you don't get it, write to PW.

11111olo wrote:

I don't know what your concept of electronics is, but you don't really have one.
You will write right away that I do not want to help and it is quite the opposite.
Help is not pointing with a finger, but directing (guiding).

Something short circuit. I do not know how it is done on this board, but usually there is a 4k7 resistor connected to Vref and a 10uF capacitor in parallel to the thermistor.
If the second thermistor shows the temperature correctly and the pull-up resistor has the correct resistance and the capacitor is not short-circuited, it all indicates that the microcontroller is damaged.

If you don't get it, write to PW.

I have no idea yet, I'm learning all the time. I appreciate your method, I came here to confirm my suspicions about the fault and not to ask for help like 'the printer doesn't work, what to do ?!'.
I checked the resistor of the second thermistor on the PCB, although I know that it would be better to desolder it, but I cannot return for warranty.
The value of 'suspect' is 1.95K, adjacent to the second good thermistor is 4.52K. Both resistors are SMD 472 like you mentioned 4.7K

You cannot measure it correctly without desoldering.
If you can take advantage of the guarantee, take advantage. I think that the repair cost will literally be a few cents, but you have to decide for yourself.

I desoldered the 4.7K resistor, it is working. To be sure, I gave a new one and unfortunately the problem is still there. There is still a capacitor, if it is not, it is possible that the controller is dead but it still transmits this lower voltage?
I would not count on the guarantee, I bought a GB from the Czech warehouse, I would have to send it back to China and the whole procedure would take at least 2 months.

After desoldering the resistor, it was necessary to check what the display shows. You can shorten this pin to ground (after desoldering the resistor, and even connect the potentiometer between ground and AVCC, the slider to the atmega pin) and you will know everything.

First, unsolder the capacitor and without the thermistor connected, it should show -14 * C (or something near it). You can check by disconnecting the second thermistor.

If atmega has fallen, maybe it is possible to use a free pin from the ADC?

Can you replace the microcontroller yourself?

Thanks for the tips, no resistor temperature unchanged, on the display 160-162 * C after unsoldering the capacitor the same. Only the display is connected, the hotbed temperature is correct, i.e. 0 * C on the disconnected thermistor.

Technically, I can replace it, I just don't know if I will program it properly.

Before you desolder, check the resistance between the ground and the ADC pin from the thermistor on the turned off electronics.

With 1.30K resistor and capacitor, with 1.18K desoldered. I measured in two ways as in the picture, correct?

If there is no damage to the PCB, the atmega must be replaced.

Burnt ATMEGA.