In many cases, we need to decide whether a component is faulty, or just wrongly installed. There are also situations where we need to decide exactly which component should be replaced. We are using the multimeter (multitester) for checking the continuity of wires, measuring the resistance values of heaters and thermistors, and measuring the voltage coming from the PSU and going to the heaters.
To get started, we first have to properly connect the two measurement probe cables to the multimeter.
Then we have to set the correct voltage or resistance range on the multimeter, depending on which component you are testing. For example, you can not measure 100K Ohm (Kilo=1000) if your meter is set to only 200 Ohm. You must set ut to 200K.
Reference for multimeter settings
If measuring the voltage going to a heater or to the printer itself it is important to remember that the MK2/S and MK2.5S are 12V systems, while the MK3S is a 24V system.
The setting is indicated by the purple arrow and will display 0 and give a beep if the two probes connect, either by touching or connected by a cable. This is to test if a wire is broken or not.
For every component, there are several options, our main focus will be on the connectors. The measurement appears on the multimeter LCD as soon as the measurement probes touch the component. To obtain the correct and relevant values, this is where you need to apply the probes:
Thermistors: metal inserts in plastic connectors | Hot end/Heat bed heater: screws holding the cables in the connector |
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Fuses can be checked by using the continuity feature on a multimeter. The only thing that will be checked is whether the component is able to conduct signals or power. By touching each of the measurement leads of the multimeter to the other end of the fuse or wire, a signal (beep or 0 value on the multimeter screen) will indicate that the component is intact and therefore, should work.
In order to check if heaters are within their range of specified resistance, the following measurements can be done. For this measurement, the multimeter needs to be set to the lowest range which includes 20Ω.
The measurement can be done on the screws in the connector for both the hot end heater and the heat bed. For the heat bed, it is also possible to probe the solder pads/screws holding down the cables. Please see the pictures above.
MINI |
Hot end heater |
[12.3 Ω - 15.1 Ω] |
Heat bed |
[4.5 Ω - 6.5 Ω] | |
MK3/S |
Hot end heater |
[12.3 Ω - 15.1Ω] |
Heat bed |
[2.0 Ω - 4.0 Ω] | |
MK2/S |
Hot end heater |
[3.1 Ω - 3.8 Ω] |
Heat bed |
[0.9 Ω - 1.1 Ω] |
In order to check if thermistors are within their range of specified resistance, the following measurements can be done. For this measurement, the multimeter needs to be set to the lowest range which includes 150 kΩ. It is common this is 200K on multimeters.
All thermistors are rated to be 100 kΩ at 25 °C. To be realistic, with a varying temperature between 20°C and 30°C, you can expect [80 kΩ - 125 kΩ].
In order to check if the correct voltage is being supplied to the heaters, the following measurements can be done. For this measurement, the multimeter needs to be set to the lowest range which includes 24V.
The measurement can be done on the screws in the connector for both the hot end heater and the heat bed. For the heat bed, it is also possible to probe the solder pads/screws holding down the cables. In this case, the connectors have to be connected to the RAMBO.
To measure, start preheating the printer to PLA and measure the component you are investigating.
The following values can be expected:
MINI |
Hot end heater |
[23V - 24.5V] |
Heat bed |
[23V - 24.5V] | |
MK3/S |
Hot end heater |
[23V - 24.5V] |
Heat bed |
[23V - 24.5V] | |
MK2/S |
Hot end heater |
[11V - 13.5V] |
Heat bed |
[11V - 13.5V] |
If you suspect the PSU is dead, and you have checked the external fuse, you can probe the terminals directly. Remove the two screws holding the cover (yellow circles) and you will have access to the power terminals.
VCC and ground (+ and -) are divided into two pairs, where the two left connectors are VCC (red arrows) and the two right connectors are ground (blue arrows). Measure one from each pair.
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If you have a question about something that isn't covered here, check out our additional resources.
And if that doesn't do the trick, you can send an inquiry to [email protected] or through the button below.