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Caterpillar ECU repair, need N548AB replacement?

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    #61
    Re: Catapillar ECU repair, need N548AB replacement?

    I'm half asleep but that didn't look much like a transistor. It doesn't seem to have a company logo either??

    It looks like a hunk of metal.

    I wonder if the device is actually a heatsink to help cool the board?
    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
    -David VanHorn

    Comment


      #62
      Re: Catapillar ECU repair, need N548AB replacement?

      CapLeaker

      But the question is have we figured out what type of device this is
      9 PC LCD Monitor
      6 LCD Flat Screen TV
      30 Desk Top Switching Power Supply
      10 Battery Charger Switching Power Supply for Power Tool
      6 18v Lithium Battery Power Boards for Tool Battery Packs
      1 XBox 360 Switching Power Supply and M Board
      25 Servo Drives 220/460 3 Phase
      6 De-soldering Station Switching Power Supply 1 Power Supply
      1 Dell Mother Board
      15 Computer Power Supply
      1 HP Printer Supply & Control Board * lighting finished it *


      These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

      1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
      2 Hem Saw Computer Stack Board

      All of these had CAPs POOF
      All of the mosfet that are taken out by bad caps

      Comment


        #63
        Re: Catapillar ECU repair, need N548AB replacement?

        thats a fucking fake!!

        take a blade and scrape the resin away between the outer pins - it's gonna reveal a bus-bar!!!

        Comment


          #64
          Re: Catapillar ECU repair, need N548AB replacement?

          Originally posted by Agent24 View Post
          I'm half asleep but that didn't look much like a transistor. It doesn't seem to have a company logo either??

          It looks like a hunk of metal.

          I wonder if the device is actually a heatsink to help cool the board?

          Look at my first post. It is clearly a fairchild device. It's heat sinked to the casing, not to the board.

          Originally posted by sam_sam_sam View Post
          CapLeaker

          But the question is have we figured out what type of device this is
          To me a regular PNP / NPN transistor does not make any sense at all. More plausible is either a diode in disguise or a mosfet of some sort.

          Haven't tried this yet, but lets say it is a mosfet. What happens if the gate isn't hooked up. There are actually schematics for other things that do show a mosfet with a floating gate. Most sense as of today in my mind in my particular case is a mosfet with a body diode and use it as a reverse fuse. Basically if something happens it will conduct drain and source pins and throw this way an error. Question here is: WHY are there 2 of them in parallel? At least it's not a dummy device with a jumper built in.

          If I put my DMM in Ohms, put my negative probe at the source pin and the positive probe to the positive side of cap C2, I get close to 600k resistance.

          Comment


            #65
            Re: Catapillar ECU repair, need N548AB replacement?

            Originally posted by stj View Post
            thats a fucking fake!!

            take a blade and scrape the resin away between the outer pins - it's gonna reveal a bus-bar!!!
            problem is the short was between the middle pin and one outer pin! Still scraping away... man... this stuff is hard!

            edit: I gave up scraping. However I did put the decapped bottom part with the middle pin under a microscope and it does reveal a little solder blob like substance sticking to the metal. I looked on at the other half top part and sure there is a tiny pinhole in the whatever this plastic is made out of. To me, that is blown Drain Source pins.
            You look at my post #60, second picture... you can see it.
            Last edited by CapLeaker; 09-25-2021, 07:15 AM.

            Comment


              #66
              Re: Catapillar ECU repair, need N548AB replacement?

              but you have no silicon wafer - there is no semiconductor on the heatsink - never was!!

              Comment


                #67
                Re: Catapillar ECU repair, need N548AB replacement?

                How thick is the metal portion in the "heatsink" portion?

                Not familiar with TO247AC construction since it was meant to be isolating, but a TO220 and TO3P the die is bonded straight to the heatsink pad which is really thick compared to the pin... so it can conduct heat away from the die.

                What I'm seeing is that the heatsink pad is ... really thin? Thin enough so that it can actually be torn?

                Die should be soldered to the heatsink pad, decapsulation usually damages die bonds. Also centered to reduce thermal resistance...

                As much damage as it's taken now, is D-S still shorted?

                Comment


                  #68
                  Re: Catapillar ECU repair, need N548AB replacement?

                  It would be interesting to find out what is this device because things are not adding up to exactly what this device is
                  9 PC LCD Monitor
                  6 LCD Flat Screen TV
                  30 Desk Top Switching Power Supply
                  10 Battery Charger Switching Power Supply for Power Tool
                  6 18v Lithium Battery Power Boards for Tool Battery Packs
                  1 XBox 360 Switching Power Supply and M Board
                  25 Servo Drives 220/460 3 Phase
                  6 De-soldering Station Switching Power Supply 1 Power Supply
                  1 Dell Mother Board
                  15 Computer Power Supply
                  1 HP Printer Supply & Control Board * lighting finished it *


                  These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                  1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                  2 Hem Saw Computer Stack Board

                  All of these had CAPs POOF
                  All of the mosfet that are taken out by bad caps

                  Comment


                    #69
                    Re: Catapillar ECU repair, need N548AB replacement?

                    oh wait, well at least I'm not the only one who hasn't fully awakened yet... of course it's not going to conduct

                    The photos are convincing to me now, SHorT.

                    Comment


                      #70
                      Re: Catapillar ECU repair, need N548AB replacement?

                      Originally posted by eccerr0r View Post
                      How thick is the metal portion in the "heatsink" portion?

                      Not familiar with TO247AC construction since it was meant to be isolating, but a TO220 and TO3P the die is bonded straight to the heatsink pad which is really thick compared to the pin... so it can conduct heat away from the die.

                      What I'm seeing is that the heatsink pad is ... really thin? Thin enough so that it can actually be torn?

                      Die should be soldered to the heatsink pad, decapsulation usually damages die bonds. Also centered to reduce thermal resistance...

                      As much damage as it's taken now, is D-S still shorted?
                      The heat sink part is thick and really heavy compared to the top part. I am talking 1.6 gram vs 4.0 grams.O.k. put it this way: the short was between the middle pin 2 and the last pin 3. Something definitely went sour inside on pin 3 and blew through that plastic and shorted out to the heat sink part on pin 2.

                      Originally posted by sam_sam_sam View Post
                      It would be interesting to find out what is this device because things are not adding up to exactly what this device is
                      No kidding... that's why I put it here. A mystery device and a weird circuit. Couldn't pass that.

                      Maybe I'll put that top part on my belt sander and see what that does.

                      Comment


                        #71
                        Re: Catapillar ECU repair, need N548AB replacement?

                        Originally posted by stj View Post
                        but you have no silicon wafer - there is no semiconductor on the heatsink - never was!!
                        Sadly I have to agree here.

                        Comment


                          #72
                          Re: Catapillar ECU repair, need N548AB replacement?

                          Originally posted by CapLeaker View Post
                          Something definitely went sour inside on pin 3 and blew through that plastic and shorted out to the heat sink part on pin 2.
                          Or as I postulated early on, it was welded that way to begin with!

                          If it was a diebond that shorted through a die... it sure would not have separated like that, diebonds are physically weak and the die soldered to the metal would hold on, and you will get the die remnants.

                          So yes, you got SHorT dummy device here and need to look elsewhere for issues, perhaps that other device that connects to these dummies -- is that shorted?

                          Comment


                            #73
                            Re: Catapillar ECU repair, need N548AB replacement?

                            Why make such a device for a dummy short. Much cheaper to put a piece of wire in!

                            Comment


                              #74
                              Re: Catapillar ECU repair, need N548AB replacement?

                              usually, mechanical/assembly reasons

                              You do realize there are 0 ohm resistors out there, full ceramic resistors that have a single black line on it... why use it when a bare wire works...

                              Just that when they have multiple SKUs using the same PCB it's easier to replace different parts than retooling the pick and place with jumpers.

                              Comment


                                #75
                                Re: Catapillar ECU repair, need N548AB replacement?

                                Originally posted by CapLeaker View Post
                                Look at my first post. It is clearly a fairchild device. It's heat sinked to the casing, not to the board.
                                Oh I must have missed that.
                                It could possibly be designed to draw heat up the pins and dissipate out through the back plate?

                                I've seen mini heatsinks on a slot A motherboard that were soldered to the board.
                                "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                                -David VanHorn

                                Comment


                                  #76
                                  Re: Catapillar ECU repair, need N548AB replacement?

                                  it's probably to make it seem unrepairable.
                                  now wouldnt it be funny if you found them in aliexpress - "surplus" from the manufacturing plant!!

                                  Comment


                                    #77
                                    Re: Catapillar ECU repair, need N548AB replacement?

                                    This might be reason that you could not find any information about the part number if it is that it is just a jumper

                                    And

                                    STJ

                                    Might be right that they want you to think that it is not repairable
                                    9 PC LCD Monitor
                                    6 LCD Flat Screen TV
                                    30 Desk Top Switching Power Supply
                                    10 Battery Charger Switching Power Supply for Power Tool
                                    6 18v Lithium Battery Power Boards for Tool Battery Packs
                                    1 XBox 360 Switching Power Supply and M Board
                                    25 Servo Drives 220/460 3 Phase
                                    6 De-soldering Station Switching Power Supply 1 Power Supply
                                    1 Dell Mother Board
                                    15 Computer Power Supply
                                    1 HP Printer Supply & Control Board * lighting finished it *


                                    These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                                    1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                                    2 Hem Saw Computer Stack Board

                                    All of these had CAPs POOF
                                    All of the mosfet that are taken out by bad caps

                                    Comment


                                      #78
                                      Re: Catapillar ECU repair, need N548AB replacement?

                                      You know, they probably did sell "surplus" TO247SHT's... easiest device to make fakes of...

                                      but then people noticed they were dead from the get go and refunded all of them...

                                      Wasn't worth it.

                                      Comment


                                        #79
                                        Re: Catapillar ECU repair, need N548AB replacement?

                                        not fakes, i mean "recycled" / "re-directed" from the official production.

                                        it happens a lot,
                                        smd stuff is on reels of 500-5000,
                                        they dont wait for the reels to run out before swapping them - where do you think the short reels of a few dozen to a few hundred parts go? in the trash? LOL
                                        there is a shopping plaza in shenzen 10 floors high - nothing but component sellers.
                                        i'm sure it's not a coincidence that it's in the same region as all the production companies!

                                        Comment


                                          #80
                                          Re: Catapillar ECU repair, need N548AB replacement?

                                          Just saying, it's just as easy to make fakes and even cheap chinese knockoffs would work as good or even better than the original at much lower cost!

                                          Comment

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