DC Motor controller repair (EOL FET replacement) - Page 1
Forum section: electronics / repair

author: scnoob
author_rank: Contributor
timestamp: February 23, 2018, 05:03:07 pm
content: I have recently acquired a dead treadmill. The issue is that when you turn it on, it tries to spin up to full speed for about one second (regardless of the speed you select), then shuts down. I have narrowed the issue down to the DC motor controller (Model MC2100). After scouring the internets, I found one blog post that said the following:"Yep, control board has a shorted HexFET and/or kickback diode. The MC2100 usually comes back to life by replacing the IRFP250 with IRFP260 or better, check current limit resistor in series with the HexFET. A good signal from the console will show a red blinking LED on the MC2100, when the controller see's too much motor current, as in a runaway, or a feedback mismatch, it kills the drive to the motor section but will leave power to the console intact usually."After opening up the controller, I have found that the IRFP250 is shorted across all 3 pins. The diode and resistor mentioned appear to be working normally. Simple enough, rip out the FET and replace it with a new one...not so simple apparently! It seems that this particular generation of FET has been discontinued and is no longer available from any of the sources I am comfortable purchasing from...They are available on EBAY, but I am not really seeing any brand name parts and who knows what kind of quality I will get, plus the slow boat from china shipping wait.So my question is this:What is an acceptable direct fit replacement FET for this part? (That is readily available on Digikey for example) I would go for a higher current capacity if possible, but I would prefer an identical pinout rather than having to do pin pretzeling to get it installed. (I had intended to go with the IRFP260 as suggested in the blog post, however it is also EOL.) I'm just not familiar enough with FETs to be able to make an informed decision on a suitable replacement. My best attempt is the IRFP260MPBF, but that's more of a guess than an educated choice.I have included a circuit diagram I found for this controller. The dead part is Q2 on the diagram, right below the motor.Thanks!!

author: ArdWar
author_rank: Frequent Contributor
timestamp: February 23, 2018, 05:16:38 pm
content: IRFP250 should still widely available. This part is such jellybean that a lot of manufacturer are second sourcing this. Quick search on Mouser still show available stock even from IRF/InfineonThe additional letters and codes behind the actual part number are usually just version identifier, either different temperature range (consumer, industrial, military), package (different TO-series, lead free, etc), or even just for different distribution packaging (reel, tube, tray).Most of the time not that matter (well, except the correct TO-package, but IRFP250 only comes in one package), unless you need a specific device for a design, or ordering in huge amount.IRFP260NPBF probably just means IRFP260, version N (whatever that means, the datasheet is identical), Pb Free packaging

author: scnoob
author_rank: Contributor
timestamp: February 23, 2018, 05:30:28 pm
content: I take it then that the IRFP260MPBF is a suitable choice? (I just noticed that the IRFP260NPBF is 32 cents more expensive and my el-cheapo kicked in haha)