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Hello! I'm almost done with assembling/calibrating my new Max V2 and I've hit a weird snag.

I successfully printed the two fan shrouds and installed them. First time turning on power, the PEEK fan turned on immediately, which shouldn't happen - hot end wasn't turned on yet. Printer display and MatterControl both reported a temp of 236 deg C, and then the printer display for temp (both hot end and bed) changed to "def". Tried to run the PID auto-tune - terminal window said "Error: PID autotune failed! Temperature too high."

Everything was working fine before I installed/connected the fans. In fact, before I wired the fans, I tested to make sure I hadn't screwed up the hot end while installing the fan shrouds, and it extruded ABS just fine. Wired the fans into the circuit, turned the printer on, and got the results described above.

Did I miss something? Please advise!

Check your wiring,,,, The Rambo board switches the ground on and off to control the fans and heaters. If the peek fan came on when you turned on the printer, you should double check your thermistor and fan wiring.

OK. Will verify fan and thermistor wiring.

BTW, running Repetier 0.91, MatterControl 1.2.2, Mac OS X Yosemite.

All the wiring looks OK. Pulled the thermistor connector out of the Rambo board and measured - should be what, 100K? I'm getting 250 ohms.

So maybe the thermistor's blown. That explains the high temp reading without trying to heat the hot end. Bed temp reporting looked OK.

There's a local electronics place that has plenty of stuff in stock, but if I have to rebuild the hot end I better know exactly what to get. Is there a topic/document that has the correct component values for the thermistor and heating resistors?

Stock SeeMeCNC thermistor is 100K NTC, Semitec #104-GT2
http://seemecnc.com/collections/parts-a ... r-100k-ntc


Ultimachine (Mfg. of the Rambo) sells a different brand 100K, Manufacturer Part No. B57560G104F
https://ultimachine.com/content/thermis ... d-w-cables
you would need to select a different type thermistor in your firmware for this one.


For a bullet proof setup I use a screw-in thermistor like this
http://www.ebay.com/itm/Modular-Screw-o ... 4ad175c679
So much better than the silly RTV glue in method stock hot end uses. IMHO
Keep in mind you do have to thread your heater block M3, buy the proper size drill bit and a good quality bottoming tap.
And remember to select the correct thermistor in firmware.

My local supplier (thank you, Vetco) has exactly those thermistors in-stock - swapped the leads and tested it in the circuit and all appears to be well. So it's time to rebuild the hot end!

In a couple of months, I plan to replace this hot end with the E3D all-metal one - I never did like the idea of wrapping the thing in Kapton after smearing it with RTV. Thanks to all for the help!