Rambo Board - Wrong thermistor temps

[Blasttiod]

Hi all,
Can someone help please.
I have changed from a Ramps 1.4 to a Geeetech Rambo 1.2g Board but just cannot get the thermistors to read the right temperatures.
What ever I try the thermistors always read twice the room temperature. For some reason they are reading 20 degrees higher than they should(ie when I am using PLA I'm running the hotend at 170 degrees where normally its 190 degrees(using Ramps board)
Thermistors type are 100K NTC thermistor

Heres what I have tried:
Different Rambo Marlin firmwares
I even copied the Thermistor.h table from my old Ramps machine to the new Rambo board but the thermistors still read the wrong temps.
I retried the thermistors with my old Ramps board and they still work as they should and show room temp at idle.

Where am I going wrong....

Regards
Kevin

[Mark]

Perhaps you should ask the manufacturer about the features of your thermistor.
Or choose the corresponding number for your thermistor here in configuration.h:

//===========================================================================
//=============================Thermal Settings ============================
//===========================================================================
//
//--NORMAL IS 4.7kohm PULLUP!-- 1kohm pullup can be used on hotend sensor, using correct resistor and table
//
//// Temperature sensor settings:
// -2 is thermocouple with MAX6675 (only for sensor 0)
// -1 is thermocouple with AD595
// 0 is not used
// 1 is 100k thermistor - best choice for EPCOS 100k (4.7k pullup)
// 2 is 200k thermistor - ATC Semitec 204GT-2 (4.7k pullup)
// 3 is Mendel-parts thermistor (4.7k pullup)
// 4 is 10k thermistor !! do not use it for a hotend. It gives bad resolution at high temp. !!
// 5 is 100K thermistor - ATC Semitec 104GT-2 (Used in ParCan & J-Head) (4.7k pullup)
// 6 is 100k EPCOS - Not as accurate as table 1 (created using a fluke thermocouple) (4.7k pullup)
// 7 is 100k Honeywell thermistor 135-104LAG-J01 (4.7k pullup)
// 71 is 100k Honeywell thermistor 135-104LAF-J01 (4.7k pullup)
// 8 is 100k 0603 SMD Vishay NTCS0603E3104FXT (4.7k pullup)
// 9 is 100k GE Sensing AL03006-58.2K-97-G1 (4.7k pullup)
// 10 is 100k RS thermistor 198-961 (4.7k pullup)
// 11 is 100k beta 3950 1% thermistor (4.7k pullup)
// 12 is 100k 0603 SMD Vishay NTCS0603E3104FXT (4.7k pullup) (calibrated for Makibox hot bed)
// 13 is 100k Hisens 3950 1% up to 300°C for hotend "Simple ONE " & "Hotend "All In ONE"
// 20 is the PT100 circuit found in the Ultimainboard V2.x
// 60 is 100k Maker's Tool Works Kapton Bed Thermistor beta=3950
//
// 1k ohm pullup tables - This is not normal, you would have to have changed out your 4.7k for 1k
// (but gives greater accuracy and more stable PID)
// 51 is 100k thermistor - EPCOS (1k pullup)
// 52 is 200k thermistor - ATC Semitec 204GT-2 (1k pullup)
// 55 is 100k thermistor - ATC Semitec 104GT-2 (Used in ParCan & J-Head) (1k pullup)
//
// 1047 is Pt1000 with 4k7 pullup
// 1010 is Pt1000 with 1k pullup (non standard)
// 147 is Pt100 with 4k7 pullup
// 110 is Pt100 with 1k pullup (non standard)

#define TEMP_SENSOR_0 1
#define TEMP_SENSOR_1 0
#define TEMP_SENSOR_2 0
#define TEMP_SENSOR_BED 1

[Blasttiod]

I used the same Thermistor as listed in my other machine which works perfectly well with the Ramps 1.4 board.

[Blasttiod]

Have also tried all the thermistor types and still the same temp reading....

[Mark]

How about running PID autotune? you can refer to the link here:http://reprap.org/wiki/PID_Tuning

[Blasttiod]

Hi, has nothing to do with PID tuning.
At idle the thermistors are showing 39 degrees when its 19 in the room. My other 3D printer is also showing 19 degrees.
Both printers are using the same brand thermistors(have also tried the new thermistors in the old printer and they work fine in that one and show the 19 degrees)
I'm beginning to think its something to do with the Rambo boards electronics

[Mark]

How about the voltage of resistor R73? It should be about 12V and 4.7V on the two sides of it, you can check it first.

[Blasttiod]

Hi Mark,
Its reading 4.1v and 12v...
Does this mean anything?

Regards
Kevin

[Mark]

So we find the problem I think, it shoud be 4.7V, there's a way you can try, change the 10K resistor(R73) to a 2K one, and you'll got 4.7V. The voltage is the standard value for comparison, if it's not precise then the temperature will be wrong.

[Blasttiod]

Hi Mark,
Thanks....
Is there another work around?.
I don't really fancy messing around with the board as the components are really small.

Regards
Kevin