[solved]pcb heated bed problem

my pcb mk2 heated bed was working fine. I set it up to 110 to print abs, and around 70º it stopped working, and does not heat up now.

i've disconnected it and check the wires, and used a hair dryer to see if the thermistor was working and it does.

i´using a sanguinololu 1.3.

what can i do to identify the problem?

Edited 1 time(s). Last edit at 10/13/2012 04:44PM by pdesigns.

A very rough back-of-napkin troubleshoot guide without any disconnections

1. Check the voltage on the input side, ie, the power supply voltage that supplies the heater.
Fail? Check/fix power supply (connector, wiring, supply itself...)
Pass? go to step 2

2) Check the voltage at the output of the sanguinololu controller board (of course the MK2 port) with the heater enabled to verify that the FET is being switched on.
Fail? got to step 3
Pass? Check wiring to heater and solder connections on MK heater board

3) Check the gate pin on the FET with the heater enabled. There should be a 3-5V signal present. (I would say 5V but I'm unsure what the sanguinololu uses as it's "logic high" to drive the heater FET)
Fail? Soft/Firmware failure or (possibly though unlikely) blown IO port
Pass? Most likely? Bad/blown FET

tanks

the problem was solved.
i had to replace one wire.

Hi, Im having a similar problem.
It seems that there is no 5v signal present at the gate. It stays 0v
I already replaced the mosfet once and I mounted it next to the board on a heatsink with a fan.
This worked for a very long time. But then I discovered that my heated bed was heating at his maximum. Also I coulnd turn it off.
I think there might be something wrong with the board itself, but my electronic-knowledge is very limited.
Do yo uhave any advise? Is there a way to test the board? Im using pronterface.

Thank you!

VIncent


xiando Wrote:
-------------------------------------------------------
> A very rough back-of-napkin troubleshoot guide
> without any disconnections
>
> 1. Check the voltage on the input side, ie, the
> power supply voltage that supplies the heater.
> Fail? Check/fix power supply (connector, wiring,
> supply itself...)
> Pass? go to step 2
>
> 2) Check the voltage at the output of the
> sanguinololu controller board (of course the MK2
> port) with the heater enabled to verify that the
> FET is being switched on.
> Fail? got to step 3
> Pass? Check wiring to heater and solder
> connections on MK heater board
>
> 3) Check the gate pin on the FET with the heater
> enabled. There should be a 3-5V signal present. (I
> would say 5V but I'm unsure what the sanguinololu
> uses as it's "logic high" to drive the heater
> FET)
> Fail? Soft/Firmware failure or (possibly though
> unlikely) blown IO port
> Pass? Most likely? Bad/blown FET