<p>I have a &quot;classic&quot; home built 3D printer, Arduino Mega, RAMPS 1.4 with Marlin 2.0.</p>
<p>It worked, was put in storage, and now I am trying to get it running again.</p>
<p>During all of the testing phases, the PID autotune, etc., the temperature of the hotend is stable.</p>
<p>When printing, for a few layers (4-5), the temperature is OK, despite the part fan coming on and off. However, after 3-4 mm of printing the temperature just rises and rises and rises, and after 275 °C thermal protection kicks in...</p>
<p>MOSFETs have additional cooling and a fan over them.</p>
<p>I'm out of ideas... Help!!!</p>
<p>My config files and G-code are <a href="https://github.com/hergiz/singles" rel="nofollow noreferrer">here</a></p>
<p>Using PrusaSlicer.</p>
<p>Why do I see a temperature rise on the display? Last time I unplugged the printer and left it on USB power then gave it power again. During USB power temperature was steadily going down, as soon I plugged the main cable it resumed printing and the temperature rising again.</p>
<p>I did another test. 20mm above bed started printing, and got same result. I captured on video entire process <a href="https://www.youtube.com/watch?v=5_1puCo07to" rel="nofollow noreferrer">Hot end to orbit</a>. Around 2 min 30 sec the show begins.</p>

[{'answer_id': 16726, 'author': 'Thomas Weller', 'author_id': 1570, 'author_profile': 'https://3dprinting.stackexchange.com/users/1570', 'pm_score': 3, 'selected': True, 'text': '<p><a href="https://i.stack.imgur.com/1ldX4.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/1ldX4.png" alt="Left right" /></a></p>\n<p><a href="https://i.stack.imgur.com/TtrmF.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/TtrmF.png" alt="Filament sensors" /></a></p>\n<p>The MK3 has 4 pins on the filament sensor, the MK3S has only 3 pins. While you need to take the extruder apart to see that, you can also have a look at the cable instead:</p>\n<p><a href="https://i.stack.imgur.com/5C6JE.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5C6JE.png" alt="Filament sensor cable" /></a></p>\n<p>Matching the sensor, the MK3 has a 4 strand wire including blue and the MK3S has a 3 strand cable without blue.</p>\n<p><a href="https://i.stack.imgur.com/nuCqp.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/nuCqp.png" alt="Bearing clips" /></a></p>\n<p>Looking under the heatbed, you\'ll find the MK3 bearings are fixed with U-bolts while the MK3S has broader bearing clips.</p>\n'}, {'answer_id': 20198, 'author': '3DCoded', 'author_id': 35508, 'author_profile': 'https://3dprinting.stackexchange.com/users/35508', 'pm_score': 2, 'selected': False, 'text': '<p>On the LCD, the MK3 will show <strong>Original Prusa MK3 OK</strong>, while the MK3S/+ will show <strong>Original Prusa MK3S OK</strong></p>\n'}]
['https://3dprinting.stackexchange.com/questions/16729', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/29321/']