T0 / T3 failure

Hi all,
I just got a new printer (P3Steel XL) and just as I was starting to get better and better prints I kept getting thermal runaways (without actually having one). After not finding a way to fix it in the firmware without turning it off entirely I figured to rewire the Ramps board. Just for info, the thermistors gave accurate values never gave an actual runaway. After I rewired the thing, nothing worked anymore
Error being as follows in pronterface:

Error:Temperature heated bed switched off. MAXTEMP triggered !!
[ERROR] Error:Temperature heated bed switched off. MAXTEMP triggered !!

Errorrinter stopped due to errors. Fix the error and use M999 to restart. (Temperature is reset. Set it after restarting)
[ERROR] Errorrinter stopped due to errors. Fix the error and use M999 to restart. (Temperature is reset. Set it after restarting)

I am not good with electronics so I guess I screwed it up somewhere along the line so I rewired it again and started measuring currencies and resistance on multiple places (focusing on the T0/T1/T3 and thermistors ofcourse.
Now both thermistors give a nice 100k ohm as everyone is saying they should. However the pins on the ramps board only give 5v for the T0. This makes sense since the extruder sensor is set to T0 and pronterface gives a normal value for it. The bed however shos crazy values. After changing the pin layout in the firmware (swapped bed with extruder) the expected thing happened and my bed was giving a normal value and the extruder a crazy one. Annoying thing being that also T3 isnt showing signs of life when I redirect a sensor to it.

From this im concluding that only T0 is working and that I must have somehow destroyed T1 and T2.
My question is whether there is a way to a) fix this or b) re-rout the sensors to another set of pins on the board?

Im a newbie so please dont shoot me if this is a repost or something, I couldnt find anything about this anywhere.
Any help is much apreciated.

Most likely a trace or two in the mega board are burned or broken, with power off separate the mega board and follow the traces, you can scrape and solder the broken traces but if to badly damaged you will have to replace the board.

Thanks for the clarity. I couldnt find anything on the board ... But I cant wire the temperature sensors to another set of pins on the Ramps or do the "T" pins have a specific feature?

More importantly, are you sure it is the Mega that got the broken connector and not the Ramps? Im gonna buy a new one I guess because Im simply too bad at electronics to fix this in an intelligent way, I just have to know which board it is.

Could be in the ramps, but I doubt it. If you have a multimeter (if don't get one) look for broken connections on both ramps and mega.

You might be able to use other pins (servo side), but how to do it it's out of my knowledge.

Well thats a sour start then haha thanks for the help, im gonna get a new Mega

... changing pins is pretty simple - you have only to change the pin definition in the firmware (with Marlin in "pins.h").

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Quote
VDX
... changing pins is pretty simple - you have only to change the pin definition in the firmware (with Marlin in "pins.h").

You would need to add the resistor/capacitor circuit to whatever pin you changed it to, as per the 'thermistors' section of the schematic: [reprap.org]

(never looked at that before; so we have a voltage divider with the 4k7 and the thermistor, and a filter capacitor between the midpoint and ground to kill noise. 10uF seems like a huge value for that purpose, I wonder why so big?)

Edited 1 time(s). Last edit at 05/31/2016 08:14PM by JamesK.

James you are absolutely right, a 1 uf would be sufficient, but who knows.

Yeah but change it to what pins? Does the Ramps have a set of spare pins to use that are open by default and if so which ones? My best guess would be the AUX pins but I really wouldnt know.

I didnt think there were since I couldnt find anything on the web, probably been using wrong terms

Thanks for the replies, made my day to hear that I possibly dont have to spend 50 for a new board...

Edited 1 time(s). Last edit at 06/01/2016 09:00AM by Mr.Blue.

What board do you have? a mega in Aliexpress is only 8 bucks and a ramps about 4.

Yes you can use the auxiliary pins, if you use a thermocouple that's were you plugged into, any set of pins in the servo section will work.

Okey so I have figured out how to make the resistor/capacitor combination on the new pins but Im left with only one issue that I really dont understand. The thermistor connector has 2 wires running. The schematics for thermistor connection shows that a ground connection, a vcc connection (5V) and a therm connection are all necessary. Now lets say I would use the inputs on AUX-2. Which pins to use? Is there a clever way to use jumpers? Or am I interpeting the schematics all wrong?

Thanks for yout patience with me

Thanks for the tip on Aliexpress btw, that feels a lot more comfortable as backup plan. I do however like to try and keep my "Italy made" one first haha

Understand, I usually buy 3 or 4 cheap ones and keep them for emergencies.

Servo side have 3 pins, positive ground and signal, once you select which one you want to use, simply attach the circuit to it (ground and signal) and then change the function of that pin to temperature in "assuming" pins h.

Edited 1 time(s). Last edit at 06/01/2016 03:20PM by ggherbaz.

I've only used arduino with the printer, and I've never really dug in to it that much so I'm no expert, but I was under the impression you would need to use one of the A* pins for the thermistor analog input. The servos have D4, 5, 6 and 11 so don't seem suitable. I think you could use A3 or 4 from Aux1, or A5, 9, 10, 11 or 12 from Aux2. Both aux connectors also have convenient Vcc and ground pins for the voltage divider circuit.

James, you are correct like I say I'm not expert . that's why I said servo side.

Oke Im really excited, its working again!
Ive made a new thermistor compatible chain with the VCC, GND and A9 on AUX-2. I re-arranged the pins in the firmware and now finally my printer obeys me once more. However its still not perfect...
When I look at the temperature readings I see a very rough and wavy reading which starts at about 10 degrees celcius too hot (30 instead of 20). I took a 4.9K resistor instead of the 4.7K, could that make such a big difference?
Step by step im getting there, please more tips!

Oke never mind I misplaced an end stop and the Mega is fried, cant connect anymore
It was a fun experiment *orders Mega on aliexpres*

Crap..... So sorry, but hey you learned something positive. When you have time post all that you did including pins h mode so any one with same issue can get the solution without asking again in the forum.