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Heated Bed blows fuse

Posted by manutenfruits 
Heated Bed blows fuse
February 17, 2018 11:54AM

I am done building my new printer (Hypercube Evolution/ CoreXY 300x300x300) but I can't get the heated bed to work. It's wired to work on 24V, I have a 500W PSU and thee board MKS SBASE (Smoothieboard clone), everything seems to work and the thermistor reads room temp, but as soon as I set a temperature for the bed, the fuse in the PSU breaks. I measured resistance between the cables and the soldering pads of the bed and it reads 0 ohms, which from what I read it's a bad sign. It reads 0 but then the multimeter starts to slowly go higher, usually stays around 0.8 ohm. I don't think the cables are touching at the soldering points, but also seems hard to make a mistake in manufacturing in such a "simple" device. Anything else that I can try before I spend money on another one? sad smiley

This is the board I'm using [www.aliexpress.com]
It has pads 1, 2 and 3, as well as two probing points A and B.
Re: Heated Bed blows fuse
February 18, 2018 02:31AM
P= U² / R
P = 24V² / 0.8 Ohm
P= 720W
Powersupply is only 500W. There IS something wrong with the bed or the wiring. Using metal clamps/screws/springs to attach the bed can cause partially shortcuts.

Edited 1 time(s). Last edit at 02/18/2018 02:33AM by o_lampe.
Re: Heated Bed blows fuse
February 18, 2018 11:48AM
I took pictures of the shitty soldering job that I did, although it looks good they're not touching. I seem to get more resistance betweeen 2/3 and 1 than between 2 and 3, which should be a longer wire. I'm just looking for any last resort before I throw away this otherwise perfectly fine surface sad smiley
Re: Heated Bed blows fuse
February 19, 2018 03:59AM
I'm afraid the solder job is not the cause for the shortcut. It's probably the etching, that failed at one or more places. The traces are pretty close together, there might be some bridges, you could cut away with a sharpie.
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