<p>The heated bed output on my printer recently stopped working. I have an output for a second hotend. How can I reprogram this output as a heated bed output? The board is a <a href="http://www.geeetech.com/wiki/index.php/GT2560" rel="nofollow noreferrer">Geeetech GT2560 rev A+</a>.</p>

[{'answer_id': 11474, 'author': 'user77232', 'author_id': 12857, 'author_profile': 'https://3dprinting.stackexchange.com/users/12857', 'pm_score': 0, 'selected': False, 'text': '<p>If you want to use Extruder heater and thermistor 2 as a hotbed driver, then you will need to get an external mosfet, since I doubt that the extruder heater mosfet will be able to handle the required current. Then in your slicer, just remap the bed from BED to E2</p>\n'}, {'answer_id': 11481, 'author': '0scar', 'author_id': 5740, 'author_profile': 'https://3dprinting.stackexchange.com/users/5740', 'pm_score': 2, 'selected': False, 'text': '<p><em>Although it appears to be a RAMPS compatible board as described in <a href="/a/11477">this <strong>now deleted</strong> answer</a>, <strong>it is not using a RAMPS pin configuration</strong>.</em> </p>\n\n<hr>\n\n<p>To fix this in the firmware, this requires an upload of newly configured firmware to the board. See e.g. question: "<a href="/q/5848">How to upload firmware to reprap printer?</a>". For Marlin firmware (which is also loaded at the factory) You need to assign the correct board number or constant name (amongst several other things) in the <a href="https://github.com/MarlinFirmware/Marlin/blob/2.0.x/Marlin/Configuration.h" rel="nofollow noreferrer">Configuration.h</a> file. Note that this is "clearly" described by the manufacturer <a href="http://www.geeetech.com/wiki/index.php/GT2560A/GT2560A%2B" rel="nofollow noreferrer">here</a>.</p>\n\n<p>From factory, a version of 1.1.X is loaded note that version 1.1.9 is the last of the 1.x branch, the default is now version 2.x.</p>\n\n<p>From the <a href="http://www.geeetech.com/wiki/index.php/GT2560" rel="nofollow noreferrer">manufacturer of your board</a> you find that:</p>\n\n<pre><code>#define MOTHERBOARD 7\n</code></pre>\n\n<p>needs to be set. Note that using number is old, nowadays you would use a constant. For board number <code>7</code> this is the constant defined as <a href="https://github.com/MarlinFirmware/Marlin/blob/2.0.x/Marlin/src/core/boards.h#L73" rel="nofollow noreferrer"><code>BOARD_ULTIMAKER</code></a>. Note that in version 2.x this number is now 1117, so the preferred usage is the constant name <code>BOARD_ULTIMAKER</code>!</p>\n\n<p>Specifically for your board, the Configuration.h file should contain:</p>\n\n<pre>\n#ifndef MOTHERBOARD\n  #define MOTHERBOARD BOARD_ULTIMAKER\n#endif\n</pre>\n\n<p>The pin arrangement used by this board is found in <a href="https://github.com/MarlinFirmware/Marlin/blob/2.0.x/Marlin/src/pins/ramps/pins_ULTIMAKER.h" rel="nofollow noreferrer"><code>pins_ULTIMAKER.h</code></a>.</p>\n\n<p>In this pin file you need to swap the pin numbers that identify the bed and the second extruder (<code>E1</code>) thermistor pin. In this file change:</p>\n\n<pre>\n//\n// Heaters / Fans\n//\n#define HEATER_0_PIN        2\n#define HEATER_1_PIN        3\n#define HEATER_BED_PIN      4\n</pre>\n\n<p>to: </p>\n\n<pre>\n//\n// Heaters / Fans\n//\n#define HEATER_0_PIN        2\n#define HEATER_1_PIN        4 // or -1\n#define HEATER_BED_PIN      3\n</pre>\n\n<p>Note that it could be that the <code>E1</code> heater output may not be designed to take the high current load the bed requires (depends on the traces on the board and the used MOSFET; with respect to the MOSFET, <a href="http://www.geeetech.com/wiki/index.php/GT2560A/GT2560A%2B" rel="nofollow noreferrer">the manufacturer states</a> that:</p>\n\n<blockquote>\n  <p>3 55Amp MOSFET (with LED indicator, the actual output is restricted by the PCB board and the connector), all 3 MOSFET are equipped with heat sink to ensure sufficient heat dissipation and stable operation</p>\n</blockquote>\n\n<p>, implying that the MOSFETs are identical). It is therefore advised to use an external MOSFET module. This will keep the high currents away from your printer board. Such a module looks like:</p>\n\n<p><a href="https://i.stack.imgur.com/aMcjA.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/aMcjA.jpg" alt="MOSFET module"></a></p>\n\n<p>You need to wire the second extruder heater leads to the white cable, the power and the bed leads use screw terminals and are clearly labeled.</p>\n'}]
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