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ZRIB board heat bed problem

Posted by gstprecision 
ZRIB board heat bed problem
August 10, 2017 01:24PM
Hi guys, I am brand new here and also to the 3d printing world so please be easy...lol

I have a Prusa I3 variant with the Zonestar Zrib board. My heat bed stopped working a couple weeks ago, waiting on a replacement, but the place I bought it from is really slow. Anyway, before it stopped working I noticed the temperature going way past the settings then back down to zero. I checked the heat bed and when applying current directly it works no problem.

I have limited knowledge of electronic but can figure it out normally. In the next picture, in the red square, is the transistor (I believe it is what it is called) that I believe is the cause of the problem. Any way to replace it easily, it appears that the back is soldered directly on the board?

Re: ZRIB board heat bed problem
August 10, 2017 03:02PM
That is a mosfet and for someone who has electronics training it removes very easily. Someone told me that they could do it, however they used the wrong equipment, got the parts to hot, ripping the circuit board traces away from the board destroying the circuit board.

If you lookup the part on the internet and purchase it you can go the your local technical collage with an electronics department, talk the teacher/professor to have one of their students do it.
I suggest this because the local repair stores will charge 1 hour + inflated price for part to replace (customer part cannot be used).
long story short it would have cost more than New with a 2 to 3 weeks waiting for the parts.

You can use a heat gun if you have a nozzle to direct the heat only onto to the mosfet. then remove with a pair of needle nose pliers.
jump to 1:


If you have a 27 watt Weller Solder Station with temperature control and know how to use it, you can heat the legs and using a dental pick you can lift the heated legs up one at a time.
Then you can heat the mosfet tab (not the circuit board) until the solder melts completely around the mosfet, then using needle nose pliers carefully lift the mosfet from the board.

1: At this time you can smooth the solder left from under the mosfet tab on the circuit board to prepare for installation of the new mosfet.
Next the legs need to be adjusted to sit only on the connection points. Align and solder the legs first with the mosfet lying on the heat transfer solder area.
Press the mosfet down to the heat transfer area while again heating the mosfet tab while applying solder to the edge of the mosfet metal tab/Heat transfer area the solder should suck completely under the mosfet and you are done (DO NOT OVERHEAT THE MOSFET).

Soldering the Tab first makes it easier for misalignment of the mosfet.

Now aren't you glad I told your to call you local trade school to see if the have an electronics department.

Edited 8 time(s). Last edit at 08/10/2017 03:26PM by Roberts_Clif.
Re: ZRIB board heat bed problem
August 11, 2017 08:36AM
Thanks Roberts,

I will get the parts and I have a buddy here that works at an electronic shop, hope he can hook me up.

Re: ZRIB board heat bed problem
August 20, 2017 08:06PM
Well I got a new board from the guys I got the printer from, printed successfully for about 5 hours and now I have the same problem....

Any ideas?
Re: ZRIB board heat bed problem
August 21, 2017 03:18AM
That board looks like a clone of an MKS BAse.
Re: ZRIB board heat bed problem
August 21, 2017 10:47AM
That board looks like a clone of an MKS BAse.

It is really similar from what I see, except there is 2 Z-Axis motor on the ZRIB.

I would like to test out the MOSFET on the board without removing them to confirm, but don't know if this is possible or not.
Re: ZRIB board heat bed problem
August 22, 2017 08:23AM
I took the MOSFET off of one board successfully. I did some test and according to what I read online the MOSFET is toasted.

Using a FLUKE 25 meter in Diode mode I get current constantly across the gate and source, which indicates that the internals are fried.

The current MOSFET is a STB55NF06 which is supposed to be 60v 50A. It should be plenty for the heat bed (From my research), unless it is a knockoff, cheap component that does not perform to it's supposed specs.

I can easily get replacement MOSFET but they are 30A.

I will also have an external MOSFET to control the heat bed.

Any thoughts?

Re: ZRIB board heat bed problem
August 23, 2017 07:14PM
Well, not many answer/suggestions...

Anyway, I replaced the MOSFET and it now works great. I am adding an external MOSFET to take away the load from the board and hopefully it will last longer than before.

Hope this can help others.

Re: ZRIB board heat bed problem
July 29, 2019 08:26AM
Hey gst! I was having a similar problem with my zrib board, but I can't find the correct part. Can you link me a similar or the same part or take a picture of it for me?
Re: ZRIB board heat bed problem
July 29, 2019 08:46AM
STB55NF06L (part number) TO-263 (package type, also called D2PAK)

ebay has a bunch, but who knows if its fake or good or what..

From what should be good suppliers.

mouser no: 511-STB55NF06L
digikey no: 497-7462-1-ND
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