Hot end problems

Hello all,

I'm a new user to the forum, but have had my printer since the end of Dec 2013.

It's a printrbot machine that a local fellow assembled setup and sold to me.

However I have had numerous difficulties (including a mainboard failure).

Most recently, I started to print with Taulman's 645. Excellent product btw!

I did roughly 12 hours of printing with this. Printing at a recorded 245C. right at the end of this print, the PEEK tube failed and the hot end was not being held.
I replaced the PEEK tube, taped it all back up, and went to print. I got 5 layers and the new PEEK tube melted.
So I checked and the thermistor was properly in the hot end. I let it cool, went back and brought it up to temp. I was about to start a print when I saw the temp on the screen shoot up to 270 ish and then give a temp failsafe protection. I turned off the machine, pulled out the thermistor, and looked. It had popped. I just got a new batch of 100k ohm thermistors. Plugged one in, and the temp remains at 251C even when it is at ambient temperature.

I have unplugged the thermistor entirely and it gives the same reading. The moment I power it up it reads 200C then jumps to 251C. I can plug the extruder temp into the bed temp and it reads exactly the same. So clearly there is either a software or hardware fault here.

Can anyone point me in the right direction?

I have managed to find the schematic here. [reprap.org]

With following this, I believe that I likely have a failed capacitor on the E-therm circuit as the reading is way off compared to the B-therm.

I will go to my electronics store tomorrow and get a couple 10uF surface mount capacitors, and replace them, and post an update..... I hate surface mount soldering btw.... thankfully I have solder wick and sucker.

Hi cjensan,

Welcome to the forum, this is the Reprap forum and specifically the Ormerod section, you may have more luck asking in a printrbot forum like [www.printrbottalk.com]

Matt

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Limited Edition Red RS Ormerod 1 #144 of 200 - RRP 1.09fw
iamburnys Ormerod Upgrades Github
Follow me on ThingiVerse My Designs

Thanks Matt,

I had found a number of topics on this forum, hence asking again. Sorry about that

No worries, stick around, the more the merrier

Just thought you might get more relevant info from printrbot guys.

Matt

---

Limited Edition Red RS Ormerod 1 #144 of 200 - RRP 1.09fw
iamburnys Ormerod Upgrades Github
Follow me on ThingiVerse My Designs

I asked there but didn't get much more of a reponse.

Thought I should update here though.

The main chip (AT90USB1286) takes in the E-therm on pin 60. This is what has failed. It has caused an internal fault to ground with a resistance of .217ohm.
So in order to fix this, I have to replace this chip..... I can get replacement chips for around $25, but then I have to unsolder a chip with 64 pins that is smaller than the size of my thumb!!! I can do it. But what a PITA.

Anyone know if it is possible to change the code to accept the E-therm input from pin 59 or 58 of that chipset instead? From what I can see/read it is the same style input, and does not appear to currently be in use.....

I'm seriously thinking about replacing the thermistor with a J-type coupler and rewriting the code...... Then it just takes in a small mV and determines the temperature based off of that. Found lots of J-Type thermocouplers for around $14. They are much more sturdy than what is being used now. Think of it as a sensor that you really would never need to replace, or even keep a spare!