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F2 fuse burning

Posted by polkary 
F2 fuse burning
September 25, 2014 06:39AM
I have a kossel mini working and all..
Last print I smelled something burning shut down everything at once and notice that the F2 fuse looks like in the picture.
Disconnecting my heated bead fixed the issue but...
How can I have both heated bed & not burning F2 fuse? why did it happened? ideas? how to prevent?

Re: F2 fuse burning
September 25, 2014 12:47PM
desolder both PTC fuses and either replace them with proper fuses or jumper them out.

- akhlut

Just remember - Iterate, Iterate, Iterate!

Re: F2 fuse burning
September 25, 2014 12:59PM
Had the same thing happen with our RAMPS, the heatbed was drawing too much current and the standard MOSFET got very hot, the fuse got hot and burned.

The fix for us was to change the STP55NF06L MOSFET with a IRLB8743PBF or (IRLB8743). It's the one closest to the fuses.
We also put a small heatsink on the MOSFET and run a 40mm fan over them.
Both MOSFET and fuse can be found on ebay.

The fuse is rated for 11A. Not sure what the bed resistance is for a kossel mini, but our 8"x8" bed is 1.3 Ohms.
So 12v / 1.3 Ohms = 9.2 Amps so it does draw a lot of current.

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