help with ramps electronics

Hi everyone !
I'm building my first 3D printer, a reprap (I found the reproduction and open source concepts really amazing! ) .
I almost finished the mechanical part ( I had some problems, but with good knifes and imagination, I managed to resolve them :p) .

For the electronic parts, I have a ramps 1.4 as shown on the picture. I wired everything except 4 motors and the heaters to test before final installation and calibration. For the alimentation, I used an old laptop power supply, 19,5V and 3,5A (without heatbed for now).
So I uploaded a repetier firmware, transfered it to the ramps and opened repetier host before connection.
Then repetier manages to connect, everything seems to be fine, I have a temperature curve. But here come my two problems : the temperature curve fluctuates between 170 and 190 °C ( I'm in France, it is not the temperature at all :p ) and the motor does not react when I try the manual deplacement, but repetier dos not tell errors...

Any idea???
Thanks for your help

lets start with the temperature. have you well plugged the thermistor?
if yes ,did you modify the firmware to fit the thermisotr you have?

thank you for your answer

I tried to solder it again to shorts wires to test, and it still does not work. Concerning the firmware, I tested repetier and put 100K epcos for the thermistor ( I have a Honeywell 100K Thermistor 135-104LAG-J01). And I also tested with pronterface and chose 100k Honeywell thermistor 135-104LAG-J01. But still about 180°C... and it does not seem to change when I unplug the thermistor!

I just retried with pronterface, same problem only it says 42,6 °C (instead of 25°C) and still no change when I unplugged(and reset). I read about 4,7 V on the thermistor, seems normal to me.

Are the Honeywell and Epcos 100K thermistors 100% compatible? If not, you will need to create a custom thermistor table in Repetier from the Honeywell thermistor's data sheet to get an accurate temperature curve.....

I don't think they're compatible, but to avoid creating a custom table, I use the marlin firmware which has my thermistor programmed, and with pronterface for a driver :p . But I have the same problem : the temperature does not fit the ambient one at all, and nothing changes when I unplug the thermistor... And pronterface does not show any error

that's really weird that different host says different values.... you should check if the thermistor work fine, by measuring it resistance at ambiant temp, and with a hairdrier blowing on hit, to see if the resistance change...
and note the values
if you have a thermometer with a bit of range, you can make a table ohm/degrees you have measured.

I don't have a thermometer... but I tested : at ambient temperature the thermistor has a 97kOhm resistance, and when I blow a hairdryer on it, the resistance fall to 50kOhm, seems to work fine ?

but still, the value seems obsolete as the temperature curve evolves the same way with the thermistor plugged or unplugged! :s

Did you try the thermistor on either of the other thermistor input connectors, to see if your firmware may be mis-configured to use one of the other ports and not T0?????

yep, and same problem, but with 3 curves : Ex 0 and bed fluctuate around 42°C and ex 1 is on 0°C whereas I plug only one thermistor, and no change when I plug it on the T1 or on the bed thermistor...
but the curves fluctuate as if evth worked ! And btw the ramps is correctly connected, and when I unplug the usb, pronterface stops
it's driving me crazy :p

Hi guys, I have some news ( good)
But I don't understand anything about my ramps!!! I restarted it with pronterface, same problems, nothing happens.
And then a new time I tried with repetier ( retransfered the firmware etc) . And it worked ! I cannot tell how I did this as I did not touch the wires, and it finally worked ( good temperature, changes when unplug , and motor works).

So thank you very much for your help guys.
See you soon on the forum !

And If you have any question ( about what I could have done and apparently worked by luck :p) , don't hesitate !!