After the printer assembly my print bed doesnt heat up

K8200 3D Printer K8200 - Assembly and user manual
1

Hello guys,

…when i connected the printer, the software only displayed the extruder temperature. I was running all the tests to the printer until i got the “heat printbed” part. Everything was fine with the extruder temperature, but when i turned on the “heat printbed” it didn´t passed the 0.60Cº, far far away from the 50Cº…and then it slowed to 0.40/0,30º.
Then i checked the resistance of the connections between the board and the bed and all of them showed resistance values near zero, which is good, i think so. But measuring the resistence between both ends of the NTC it showed resistance near 800/900. I presumed the problem was in the NTC thermistor and i decided to resolder it. But unfortunately the problem presists…and the temperature never returned to heat up again and now the resistence in both parts of the thermistor is 1.

So, where should be the problem?..the circuits seem to be ok, i think it has something to do with the thermistor or the printbed, but i don’t know…;/

dropbox.com/s/bwkq2phbuzl3r … mistor.JPG

Thanks in advance!

2

Hi Ahab,

[quote=“Ahab”]when i turned on the “heat printbed” it didn´t passed the 0.60Cº, far far away from the 50Cº…and then it slowed to 0.40/0,30º.
Then i checked the resistance of the connections between the board and the bed and all of them showed resistance values near zero, which is good, i think so. But measuring the resistence between both ends of the NTC it showed resistance near 800/900. I presumed the problem was in the NTC thermistor and i decided to resolder it. But unfortunately the problem presists…and the temperature never returned to heat up again and now the resistence in both parts of the thermistor is 1.
[/quote]
judging from your photo, I’m afraid you resoldered a bit too much. Like any SMD part, the thermistor needs only a small amount of solder underneath its pads to connect to the PCB. However, your error seems to be more in the opposite direction, i.e. it’s not short-circuited as one would suspect at first, but rather disconnected (I presume the multimeter did show “1” indicating overrange, and not “1.0 kΩ” or similar, right?).
If you have some equipment for desoldering, you can try to get the thermistor off the board in one piece. When using a solder sucker, make sure the thermistor doesn’t get lost in it, e.g. by holding it with tweezers when desoldering the second side. If successful, measure the disconnected thermistor to assess whether it’s ok or broken.

As for the board, you can test the heated bed input by switching the thermistor connectors. Both inputs have the same calibration, hence the indicated temperature on the input where the (working) extruder thermistor is connected should be the same, too.

Cheers,
kuraasu

3

[quote=“kuraasu”]Hi Ahab,

[quote=“Ahab”]when i turned on the “heat printbed” it didn´t passed the 0.60Cº, far far away from the 50Cº…and then it slowed to 0.40/0,30º.
Then i checked the resistance of the connections between the board and the bed and all of them showed resistance values near zero, which is good, i think so. But measuring the resistence between both ends of the NTC it showed resistance near 800/900. I presumed the problem was in the NTC thermistor and i decided to resolder it. But unfortunately the problem presists…and the temperature never returned to heat up again and now the resistence in both parts of the thermistor is 1.
[/quote]
judging from your photo, I’m afraid you resoldered a bit too much. Like any SMD part, the thermistor needs only a small amount of solder underneath its pads to connect to the PCB. However, your error seems to be more in the opposite direction, i.e. it’s not short-circuited as one would suspect at first, but rather disconnected (I presume the multimeter did show “1” indicating overrange, and not “1.0 kΩ” or similar, right?).
If you have some equipment for desoldering, you can try to get the thermistor off the board in one piece. When using a solder sucker, make sure the thermistor doesn’t get lost in it, e.g. by holding it with tweezers when desoldering the second side. If successful, measure the disconnected thermistor to assess whether it’s ok or broken.

As for the board, you can test the heated bed input by switching the thermistor connectors. Both inputs have the same calibration, hence the indicated temperature on the input where the (working) extruder thermistor is connected should be the same, too.

Cheers,
kuraasu[/quote]

Hello Kuraasu!

Thanks for the help!

Yesterday i figured out a solution, but now i am facing another one, which i dont know if it has something to do with this latest problem:

I took off the thermistor, which was broken after the “desoldering” process, and put another one (not an smd, but the other resistance with 2 legs :wink: ), and then i measured the wires and they showed 6.6K (strange isnt it?) in the 200k mode in the multimeter, but the truth is that the program started to work and recognized the temperature (about 20º). Then i heated it up and it reached the 50º. Perfect!

Today i was finishing the calibration process and i was stuck in the bed flattening process…well, when i decided to move on to the printing experience the Bed temperature was on 250º! GRRRRR!!!..

Did i comitted some mistake while flattening the bed??

Now if i measure the wires from the thermistor to the therm 2 they all measure 0.00.

I have restarted the board, have resolder the thermistor again and the problem persists…250º in the bed!

Damn…what an headache this k8200…;(

Any solution??

Help would be much appreciated!
Thanks!

(BTW…Why did it work measuring 6.6k??? )

4

Hi Ahab,

where did you measure those 6.6k? Between both contacts of the connector? Was it unplugged at the time?

Cheers,
kuraasu

5

Hi!

I measured 6.6k between both contacts of the thermistor, and between them and their correspondent in the board!..

What do you think that could be wrong?

Is there any short?..but how, if everything was ok?

6

You left out one question - was the THERM connector plugged in or not?

The 100 kΩ should be measured with the connector unplugged, otherwise the voltage applied by the board will interfere with the multimeter.

7

Ah ok!

It wasnt unplugged! :/…sorry but i’m not a pro in electronics! :slight_smile:

Now it measures 140k all along the WIRELESS, between the thermistor and the board!

And the bem still measures 250º! :confused:

Any clue about this?

Much Thanks for your attention!

Cheers

8

*not WIRELESS but “wires”

Damn the auto correction! :wink:

9

Hi Ahab,

that’s good (a bit high though, room temperature below 20 °C?). If you “heat” up the bed e.g. by putting your hand on it, does the value change? It should get lower with rising temperature.

How about the extruder / hotend thermistor, is it working? If yes, measure its resistance for comparison.
Switch the connectors of both thermistors on the controller board and check in Repetier Host whether the indicated temperatures are switched, too.

Cheers,
kuraasu

10

Hello!

Today the temperature is about 20º.

Connected Extruder: 21º
Bed: 253º

After pushing the “heat bed” button it lowers down to 251,7 º. But nothing more happens.

Now that you asked for, i realize that the extruder doesn´t heat up also, but it was working since the very begining!..strange!..maybe this problem has something to do with the board?

I measured the resistance again in both thermistors and now they round up for 120k (bed and extruder).

Then if i switch the connectors of both thermistors on the controller board the temperatures remain the same:

connected extruder: 21º bed: 251,60º

Do you figure out something?

Thanks Kuraasu!
Cheers!

11

Hi Ahab,

so, did I get this …

  • bed thermistor on bed input (THERM2) reads 253 °C

  • hotend thermistor on extruder input (THERM1) reads 21 °C

  • bed thermistor on extruder input (T.1) reads 21 °C

  • hotend thermistor on bed input (T.2) reads 251.6 °C

… correctly?

That would point to an error on the circuit board, either on the THERM2 input socket or (which would be very unfortunate) inside the ATmega.

Just to be sure, can you test all four configurations mentioned above for changes in the temperature reading? Just heating up the bed or the heater block with your hand (or, alternatively, with a hairdryer) should be enough to get some clear changes in the indicated temperature.

Cheers,
kuraasu

12

[quote]Did i comitted some mistake while flattening the bed??[/quote]What did you do exactly to flatten it?

13

[quote=“kuraasu”]Hi Ahab,

so, did I get this …

  • bed thermistor on bed input (THERM2) reads 253 °C

  • hotend thermistor on extruder input (THERM1) reads 21 °C

  • bed thermistor on extruder input (T.1) reads 21 °C

  • hotend thermistor on bed input (T.2) reads 251.6 °C

… correctly?

That would point to an error on the circuit board, either on the THERM2 input socket or (which would be very unfortunate) inside the ATmega.

Just to be sure, can you test all four configurations mentioned above for changes in the temperature reading? Just heating up the bed or the heater block with your hand (or, alternatively, with a hairdryer) should be enough to get some clear changes in the indicated temperature.

Cheers,
kuraasu[/quote]

Hi there Kuraasu!..once again thanks for the great help!
I have just runned your tests and we might have some conclusions:

  • bed thermistor on bed input (THERM2) reads 89.70 °C
    After using the hairdryer during 1min the temperature rises to 97º.

  • hotend thermistor on extruder input (THERM1) reads 226.90 °C
    After using the hairdryer during 1min the temperature remains the same.

  • bed thermistor on extruder input (T.1) reads 226.90 °C (“connected extruder:226.90 ºC”)
    After using the hairdryer during 1min the temperature remains the same (clicked the heat extruder button).

  • hotend thermistor on bed input (T.2) reads 91.50 °C (" Bed: 91.50 ºC ")
    After using the hairdryer during 1min the temperature rises to 102 ºC (clicked the heat printbed button).

Is there any problem in Therm1 input socket?..or is it about the ATmega?

Hope we can reach the solution because i really need this printer working!

By the way, here is a photo of the thermistor that i am using in the bed (which already worked!):

dropbox.com/s/8js3ci1fex3elon/IMG_2370.JPG

Cheers!

14

Hello guys!

I followed exactly what the manual tells to do:

“If the bed is a bit too high here press it down slightly. The HEATED BED, CARDBOARD ISOLATOR and ALUMINIUM BED PLATE can be forced a little bit until the bulge in the middle is gone.”

Used the thumb screws also and tried to force a little bit the bulge in the middle. Unfortunately it maintained the same and i proceed to the next chapter when i found the temperature problem. ;(

Can you help me?..i’m stuck on this and i really need to move forward!

Thanks in advance!
Cheers!

15

Hello guys,

Any idea of how to solve this?

Your help would be much appreciated!

Thanks!

16

I’m afraid there’s no way to solve this except changing the board. The TERM1 A/D circuit must be fried.

17

What does Repetier say the temp of the bed and the extruder after you connect to the printer.
If the bed reports 0C unplug therm 2 and check the resistance across the pins of the plug.
It should read about 100K at room temp.

18

Hi there Wrong Way,

After connecting the printer the software informs:

Connected Extruder: 227.00º/Off Bed:88.70ºC/Off

So, the conclusion is that the board is disfunctional?

19

Hello,

Maybe not there are some things you can try to isolate the failure.
Try swapping therm 1 and therm 2
and check the software to see if the temps swap around.

You have.
Connected Extruder: 227.00º/Off Bed:88.70ºC/Off
If you get the following after the swap
Connected Extruder: 88.70º/Off Bed:227.00ºC/Off
That would indicate the board is OK.
Next measure the resistance at the plug of therm1 and therm 2
@ room temp they should be around 100K ohms
If not check the wiring you may have a short.

Also if they are unplugged the software will report 0C for both the bed and extruder.

I hope this helps.

20

[quote=“Wrong Way”]Hello,

Maybe not there are some things you can try to isolate the failure.
Try swapping therm 1 and therm 2
and check the software to see if the temps swap around.

You have.
Connected Extruder: 227.00º/Off Bed:88.70ºC/Off
If you get the following after the swap
Connected Extruder: 88.70º/Off Bed:227.00ºC/Off
That would indicate the board is OK.
Next measure the resistance at the plug of therm1 and therm 2
@ room temp they should be around 100K ohms
If not check the wiring you may have a short.

Also if they are unplugged the software will report 0C for both the bed and extruder.

I hope this helps.[/quote]

Hi wrong way!
Thanks for the aid!

So, following your steps:

1: If i switch the therm 1 for therm 2 the temperatures are still the same;
2: if i measure the resistance at the plug of therm 1 and therm 2 they measure 125k.
3: If i unplug both therms the software reports the same:

Connected extruder: 227.80 ºC Bed: 87ºC

The board is “damaged”, is this the answer?

Thank you again guys!