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My Anet A8 suddenly had issues with being unable to heat the bed. After ruling out software issues, I disconnected the connector and found this (sorry for the terrible quality):

Faulty connector: left male, right female, indicator on the burnt pin

The left most pin on the male connector (bed) is also charred. How could I best repair this?

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Owning an Anet A8 I confirm that the connectors are not rated for the amount of current that pass through them. You do not need a new bed unless the heat element has burned through (but that is pretty uncommon, it usually is the connector). This burning of the bed connectors is a very well known problem of the Anet A8 printers; these connectors are just not rated for the current and the movement of the bed. It is best not to use a connector at all! And yes, the Anet A8 default printer firmware does not have any build in protection for thermal runaway! It is always advised to immediately flash another firmware, e.g. Marlin firmware.

The best repair is to get some high quality silicone AWG 14/16 wires and solder these directly onto the back of the pins of the connector. Also crimp forks to the other end to connect the wires correctly to the printer board.

What I did was cutting up the connector to leave only the 2 middle pins (for connecting the bed thermistor, which does not use much power) and soldered the red wire to the left 2 pins and the black to the right 2 pins. You can do that at the back side of the socket where the pins make an angle.

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  • $\begingroup$ Why exactly do you advice to solder it to 2 pins? I'd expect pins 2 and 5 to be unconnected? $\endgroup$ Dec 24 '18 at 19:16
  • $\begingroup$ @DaniëlvandenBerg Because 2 pins for 12 V connections (+ and -, not that this matters by the way) are connected to the heating element each (etched copped resistor elements). This was at my bed, please look into your own bed if 2 pins are connected to the heating elements! $\endgroup$
    – 0scar
    Dec 24 '18 at 20:16
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New Bed (Connection)

You will at least need a new female connector, but as the connector burnt, you have some underlying problem that made the connector burn in the first place: either the board is sending bad signals to the bed, or the bed is not rated for the board or you just had a faulty connector (the most usual culprit). Honestly? Replace the whole connector for a properly rated and intact pair - these pin connectors are not rated for 12 V at all but for 5 V!

If you don't use a beefier connector, solder the wires directly to the bed.

Safety first!

Anet isn't known for good firmware implementation of safety, so make twice sure that you run a firmware that has Thermal Runaway Protection enabled!

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  • $\begingroup$ Thanks for the advice. (Fortunately) I already had Skynet running, which indeed includes TRP. $\endgroup$ Dec 24 '18 at 19:15
  • $\begingroup$ @DaniëlvandenBerg Skynet3D is obsolete, but good that you at least changed it! $\endgroup$
    – 0scar
    Dec 24 '18 at 19:49

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