[Solved] Heatbed Problems + Burnt MiniRambo Board  

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Disibaro
(@disibaro)
New Member

After using my MK2 for two years, and a bad day with some failed prints, the room fills with a bruning plastic smell that I shruged off as the smell of the new PLA filament I was trying out, but then I notice the heatbead is heating up way over the configured temperature. Restarting the printer and trying other models did nothing since as soon as the printer boots up the bed starts heating up on its own. 

Flashed new firmware and checked all the cables and tested the conections for any broken cables with a Multimeter but got no results. After all the tests decided to check on the motherboard itself and I came across this sad scene:

A thing I find odd is that all the fuses are unburnt even though the chip clearly got some heat.

Is there any chance to salvage the board? Or my only chance is to get a new one?

Best Answer by Vojtěch:

Is there any chance to salvage the board? Or my only chance is to get a new one?

Replacing the MOSFET is the only way. Best done with a hot air rework station and a good soldering iron, but you can wing it, too. Cutting all the four pins, leaving the MOSFET in place and soldering a big TO-220 MOSFET with a heatsink to the same pins is a crude, yet effective way.

The original is a PSMN7R0-60YS. A cheap, more powerful replacement in a TO-220 package would be eg. IRFB3306.

Posted : 05/05/2019 4:20 pm
vintagepc
(@vintagepc)
Noble Member

The  MOSFET is probably failed short. Unless you have the skills and gear to replace it, you'll need a new board...

Posted : 05/05/2019 4:57 pm
Disibaro liked
Vojtěch
(@vojtech-p6)
Honorable Member

Is there any chance to salvage the board? Or my only chance is to get a new one?

Replacing the MOSFET is the only way. Best done with a hot air rework station and a good soldering iron, but you can wing it, too. Cutting all the four pins, leaving the MOSFET in place and soldering a big TO-220 MOSFET with a heatsink to the same pins is a crude, yet effective way.

The original is a PSMN7R0-60YS. A cheap, more powerful replacement in a TO-220 package would be eg. IRFB3306.

This post was modified 1 year ago by Vojtěch
Posted : 05/05/2019 5:12 pm
Disibaro liked
Disibaro
(@disibaro)
New Member
Posted by: Vojtěch

Is there any chance to salvage the board? Or my only chance is to get a new one?

Replacing the MOSFET is the only way. Best done with a hot air rework station and a good soldering iron, but you can wing it, too. Cutting all the four pins, leaving the MOSFET in place and soldering a big TO-220 MOSFET with a heatsink to the same pins is a crude, yet effective way.

The original is a PSMN7R0-60YS. A cheap, more powerful replacement in a TO-220 package would be eg. IRFB3306.

Thanks a lot for your detailed explanation 🙂

I'll give it a try with a friend that has the right tools for the job!

Posted : 05/05/2019 9:07 pm
Disibaro
(@disibaro)
New Member

Just wanted to give an update, I ended up ordering the original mosfet model and replaced it on the board. 

Everything is working like a charm 👍 

Thanks again for your help 🙂

Posted : 06/07/2019 8:30 pm
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