IRFZ44N replaces IRLB8743 on Ramps?
April 06, 2019 04:46AM
Hi all.

Need to determine ( with little electronics knowledge or understanding ) if I can replace the IRLB8743 mosfet, used for the bed heater, with a IRFZ44N mosfet ?

reason : Printer runnning fine for 2 years. Marlin on Mega with Ramps.

Tonight at end of a 3 hr print I smell hot electrics.
6 layers to go so I let it finish.
Then the graphic LCD display shows 'Err: maxtemp bed' and I see the bed temp at 250C ( same as the max setting in the config file ).

I reset the Mega after the print completed and allowed it to cool.

First suspicion was a faulty wire to the bed thermistor. So powered-on and moved the bed ( Y axis on Prusa i3 style printer ).
There were no sudden changes to the thermistor reading as I would expect with a damaged wiring harness

Instead, the bed temp started climbing non-stop to over 70C before I turned off the power.

The mosfet on the Ramps board for the bed heater is very hot, so I suspect that it is faulty and is stuck in an 'always on' state.

I am unable to get a replacement IRLB8743 ( we are in Africa, and at the start of a long weekend ) but I do have a few of the IRFZ44N mosfets.

Can I use those instead ?

cong ty dich vu giup viec nha chung cu quan 11 gia re, giup viec nha tphcm tron goi
Re: IRFZ44N replaces IRLB8743 on Ramps?
April 06, 2019 04:50AM
You can if your desperate, but it will run hot, 100-200 degrees C. It will need a heat sink.
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