Faulty control board?

Hi,

Following on from yesterday evening’s failure to get all the stepper motors up and running, I have now diverted attention to the extruder and bed temperature sensing and control.

1/ extruder temperature sensing and control has worked. hooray :slight_smile:

2/ Therm2 / bed temperature is indicated in Repetier as 0.0degC. Disconnecting the sensor wiring from the controller board I measure around 140kohms (at ambient) across the connector terminals whereas the extruder temperature sensor + wiring resistance measures around 127kohms (and I note that the two sensors are different) so surely the controller shoudl be able to come up with a temperature. When the sensor is reconnected to the controller the voltage across the sensor connector terminals measures 4.997V - doesn’t sound right to me as this is a potential divider???
Swapping the bed and extruder connections over on the controller results in the bed temperature being reported and not the extruder. Looks like there is something wron with the Therm 2 / bed temperature senor input on the controller?

3/ Fan control in repetier: Well I tested the control in Repetier by switching the fan on but it won’t switch off? Is this a software bug that is known about? or lets try a ‘power cycle’… OK, killed the power and left for 10mins, then reconnected and the fan +(fan LED) energised. I press the reset button on the control and a short time later the fan stopped and Led extinguished. Now trying to switch on the fan in Repetier doesn’t switch the fan on??? Something seems to be a bit dodgy? Having now monitored the fan control output line from the controller’s processor. I get a 0-5V digital output corresponding the the fan control in Repetier. Looks like there is a fault with the power stage MOSFET?

Looks like the controlller needs to be replaced…

kind regards

Geoff

Just a guess, did you use an Arduino version above 1.0.6 to flash (upload) the firmware?
If so, that is the issue. Only the old 1.0.6 Version compiles the firmware correctly, as some libraries were changed
in the newer arduino versions.

Hi,

Thanks for info. I did download the ‘latest’ software. I will try to revert to an earlier version and let you kniow how I get on.

many thanks

Geoff

Hi,

I have just downloaded Arduino 1.0.6, recompiled to Marlin file & downloaded to the controller. Upon restart of the K8200 in Repetier I still get 0.0degC displayed for the bed temperature. If I swap the temperature sensors around, the Extuder shows a plausible temperature whilst the bed still indicates 0degC.

Can we conclude that this is a faulty controller?

regards

Geoff

You could check the solder joints on the pins for the bed on the control card.
Make sure they are good.

This is just a guess

Hi,

Thanks for suggestions. I will try to trace the signal path from the senor back to the uC pin. I suspect the fan issue I am having is a solder joint quality issue.

regards

Geoff

Hi,

Temperature sensor input:
I have now had a closer look at the controller PCB assembly. I connected a 100kohm resistor across the thermistor temperature sensor inputs ‘Therm1’ and ‘Therm2’ in turn whilst measuring the voltage across the terminals. Therm1 measured 4.8V indicative of a potential divider whilst Therm2 measured 5.0V (The same as the 5V rail) indicating that the pull-up resistor is a short circuit OR the microcontroller input pin is behaving as an output. Visual inspection of the pull-up resistor and surrounding temperature sensor circuitry looks OK. A support ticket has now been raised…

Fan:
Having looked at the controller PCB assembly under a microscope one of the legs of the fan controlling MOSFET was not joined to the PCB with solder. A rework of this joint has now got the fan controller side of things working…