Announcement

Collapse
No announcement yet.

Benchtop Pro MD95 Dremel Burnt resistor now works at Full speed only

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Benchtop Pro MD95 Dremel Burnt resistor now works at Full speed only

    Guys need your help.
    I believe it got wet a bit which then cause it to only run at full speed, no longer can adjust speed.

    Opened up and notice burn near resistor. I guess I need new resistor but what value? I did not test any further, I guess I can remove resistor and check.

    Let me know what you think. Also what is ntc 60?
    Attached Files

    #2
    Re: Benchtop Pro MD95 Dremel Burnt resistor now works at Full speed only

    I would guess the triac is shorted, looks like that resistors been running hot for a while and it may still be ok. Remove it and check its value, look and see if there are any values still visible on the resistor
    Last edited by R_J; 06-04-2018, 04:02 PM.

    Comment


      #3
      Re: Benchtop Pro MD95 Dremel Burnt resistor now works at Full speed only

      Remove it but didn't see any values on the resistor. It did measure 5.2 ohms with multi meter. Which one would be the triac?

      Comment


        #4
        Re: Benchtop Pro MD95 Dremel Burnt resistor now works at Full speed only

        yes the triac is suspect . or the pot is damaged .. maybe still damp .

        Comment


          #5
          Re: Benchtop Pro MD95 Dremel Burnt resistor now works at Full speed only

          triac is the one with 3 legs

          Comment


            #6
            Re: Benchtop Pro MD95 Dremel Burnt resistor now works at Full speed only

            Thanks Guys, the trace near the resistor was lifting so I glued it back. Once I but it back I will retest.

            Comment


              #7
              Re: Benchtop Pro MD95 Dremel Burnt resistor now works at Full speed only

              Remove the old solder and resolder the resistor, if the trace is bad just replace it with a piece of wire, Provide the number off the triac (3 leg part) if there is one.
              Last edited by R_J; 06-04-2018, 05:51 PM.

              Comment


                #8
                Re: Benchtop Pro MD95 Dremel Burnt resistor now works at Full speed only

                It looks like the speed controller was overloaded, cooked the resistor and triac. The NTC was useless, it was supposed to limit power.

                Drew a schematic but not sure what the cooked R3 resistor's value is.
                The circuit did not make sense unless there is a diac or something underneath the hot glue blob.

                If you can give the resistor ohms and triac part number, I will update the sch.
                Attached Files

                Comment


                  #9
                  Re: Benchtop Pro MD95 Dremel Burnt resistor now works at Full speed only

                  WOW, thanks

                  The resistor is mwntion above at 5.2 ohms
                  triac is Z0409MF A149

                  Sorry had no time to mess with unit.

                  Comment


                    #10
                    Re: Benchtop Pro MD95 Dremel Burnt resistor now works at Full speed only

                    It's very likely the triac shorted, that would cause the motor to run full speed

                    Comment


                      #11
                      Re: Benchtop Pro MD95 Dremel Burnt resistor now works at Full speed only

                      I will remove and try to test it.

                      Comment


                        #12
                        Re: Benchtop Pro MD95 Dremel Burnt resistor now works at Full speed only

                        Problem solved, appears it was the Pot, I cleaned it and now have variable speeds..

                        Comment


                          #13
                          Re: Benchtop Pro MD95 Dremel Burnt resistor now works at Full speed only

                          If you can find a new pot I would recommend replacing it
                          It might do the same thing again
                          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

                          Working...
                          X