trying to heat the bed causes the printer to power off/restart

TheOzz

So I have never been able to print with this printer and I have had it for a couple months now. I have just found the pronterface application and using this I found the error message below. I believed the error had something to do with my printer bed but I have replaced the bed heating wire and the motherboard yet the issue has persisted. I ordered it from Banggood and they have NO intentions of refunding me or replacing the printer. If anyone could help it would be greatly appreciated. Thanks!

Here is the error message that I copied and pasted off of pronterface when I try and heat up the heating bed:

temperature to 60.000000 degrees Celsius.

SENT: M140 S60.0

RECV: M140 S60.0

SENT: M105

RECV: echo:

RECV: ok

RECV: ok T:35.6 /0.0 B:28.2 /60.0 @:0 B@:0

RECV: M105

RECV: #power down

RECV:  LCD ID:9341

SENT: M105

RECV:  LCD ID:9341

RECV: help

RECV: A5S-2019-01-03 14:13:22

RECV: ->LCD ID:9341

RECV: <#>EEPROM is OK!<#>external FLASH IC is OK!

RECV: ->language id :1

RECV: <#>FLASH mount FATS OK!

RECV: <@&gt;SD card mount FATS fail!

Samuel Pinches

Welcome @TheOzz

I just saw this post, after the last one. It sounds like there is almost definitely a short circuit. Presumably heating the nozzle works fine? If you have a multimeter, can you unplug the bed heating wires on the motherboard, and check the resistance between the red and black wires that go to the bed?

TheOzz

Thanks @Samuel Pinches !

Heating the nozzle does work fine! and I have replaced the red and black wires that go to the board and the problem hasn't gone away. Thus, Im thinking those shouldn't be the problem. Yet, I will check the resistance and get back to you! thank you

Samuel Pinches

The power supply is 350W, 24V

P = V * I

I = 250 ÷ 24 = <11A

V = I * R

R = 24 ÷ 11 = 2.2 ohms

So if resistance is less than 2.2 ohms, then there is probably a problem with the bed or the bed cables. Otherwise could be a fault on the motherboard, or more likely, on the power supply.

TheOzz

Hello @Samuel Pinches

 Ok, I just checked the resistance of the wires and they are roughly around 2.2 Ohms. Also, I had already replaced the motherboard. So I'm thinking it must be the power supply you had mentioned. Is there a way to check if that is the problem? and what exactly would the fault be of the power supply that is causing this problem? Thanks again!

Samuel Pinches

Ok, here are three more tests:

• Try enable the bed with the bed disconnected. It should not restart immedately, but will restart eventually with a heating failure error in pronterface. If that restarts immediately however, it is a motherboard fault.
  
• Try to heat the bed, with the nozzle heater in the bed heater connector, and the thermistors plugs swapped. That should work fine when you heat the bed. If that fails, it is also a motherboard fault.
  
• Try to heat the bed, by connecting it directly to the main power supply 24V +/- output. It should get hot and reach about 120C (so be careful!). If the power supply light goes off when you turn it on, then you know it has failed and needs replacement.
  

TheOzz

Hello @Samuel Pinches

Awesome! I will go about doing these tests hopefully by the end of the day and hopefully figure out what is at fault here. Thank you so much!