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Blown cap on old dwell gauge - kal equip 2851

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    Blown cap on old dwell gauge - kal equip 2851

    Hi,

    Can anyone help ID this cap, or any tips on how to figure it out? As you can see, it's clearly fried. Unfortunately the burn marks obscured the color bands. I couldn't get a good zoom on it with my phone, so I hope the pics are enough. I can try again if not.
    Attached Files

    #2
    Re: Blown cap on old dwell gauge - kal equip 2851

    looks more like a resistor to me ..what does it connect to ?

    Comment


      #3
      Re: Blown cap on old dwell gauge - kal equip 2851

      Looks like a resistor to me also, post a clear picture of the trace side of the board. Also post the number on the component next to the burnt resistor.
      Last edited by R_J; 07-11-2022, 08:34 PM.

      Comment


        #4
        Re: Blown cap on old dwell gauge - kal equip 2851

        Thanks both for the quick replies. Sorry I couldn't respond until now.

        Attached are pics of the trace side and (I hope) a clearer pic of the numbers of nearby components.

        I believe it connects:

        The very purple resistor (?) to the left of it
        The black three post component (not sure what it's called)
        Two white 'blocks': .1J100# and (horn?)33nJ250 (obviously not so sure on the symbols)
        Attached Files
        Last edited by snakeintheeaglesshadow; 07-19-2022, 10:58 PM. Reason: More info and correction

        Comment


          #5
          Re: Blown cap on old dwell gauge - kal equip 2851

          desolder it and check its resistance

          Comment


            #6
            Re: Blown cap on old dwell gauge - kal equip 2851

            looks like a track got burned through .

            Comment


              #7
              Re: Blown cap on old dwell gauge - kal equip 2851

              I followed the circuit a bit, but can't tell what all the wires go to. The burnt resistor connects to the red wire near the LED, see pic.

              I would say it's 82R based on the grey band and smoke, so power shorted to that wire. It's a weird fault, someone must have connected up the wires wrong to the board. +12V power is supposed to connect to the top right corner. The CD4069 IC then gets 9VDC power.

              OP a resistor does not burn up unless there is an overload caused by another issue. So replacing the resistor will just smoke it again. The other resistor looks OK it just has a purple body. I can't see any cooked pcb traces, it's just solder-dipped might appear that way?
              The transistor typically connects to the ignition coil/points, but here it's missing all the surge protection parts so I'm not sure where they are.
              Attached Files

              Comment


                #8
                Re: Blown cap on old dwell gauge - kal equip 2851

                here doesn't look right ..
                Attached Files

                Comment


                  #9
                  Re: Blown cap on old dwell gauge - kal equip 2851

                  that transistor looking thing might be shorted ..best check its id number then test it .

                  Comment


                    #10
                    Re: Blown cap on old dwell gauge - kal equip 2851

                    Originally posted by petehall347 View Post
                    here doesn't look right ..
                    You're right trace should be flat but I have seen that as a solder blob from the tinning process, on PC boards made in the 1980's like this one.

                    The dwell meter reminds me of Sun, Sears Craftsman etc. circuits. PCB marked 01-4221B so it might be made by them.

                    Comment


                      #11
                      Re: Blown cap on old dwell gauge - kal equip 2851

                      Yeah that's a res. Can you read the colors on it ? And yeah check whatever it is connected to.

                      Comment


                        #12
                        Re: Blown cap on old dwell gauge - kal equip 2851

                        a lot of times a resistor can get that hot and still work - it just got very hot from the real fault
                        so always worth metering it

                        Comment


                          #13
                          Re: Blown cap on old dwell gauge - kal equip 2851

                          Wow what great input! Very impressed by this community.

                          Originally posted by redwire View Post
                          I would say it's 82R based on the grey band and smoke, so power shorted to that wire.
                          Can you recommend a specific resistor(s) to try?

                          Originally posted by redwire View Post
                          It's a weird fault, someone must have connected up the wires wrong to the board. +12V power is supposed to connect to the top right corner. The CD4069 IC then gets 9VDC power.
                          I found it among my late father's hot rod stuff. No instructions of course, so I just plugged it up. Incorrectly, obviously.

                          Originally posted by redwire View Post
                          The transistor typically connects to the ignition coil/points, but here it's missing all the surge protection parts so I'm not sure where they are.
                          Ah ha! I think I know where I went wrong attaching it. With no surge protection built-in, must be pretty easy to fry.

                          On the attached pic I attached the each colored lead to it's corrsponding connector on the board. I'm thinking the correct attachment points to engine are:

                          Red = ignition coil positive
                          Black = ground
                          Blue = ignition coil negative
                          Inductive pick-up = spark plug wire

                          Originally posted by stj View Post
                          desolder it and check its resistance
                          Would this work even if blown? I figured it stops 'resisting' when such.
                          Attached Files
                          Last edited by snakeintheeaglesshadow; 07-21-2022, 11:20 AM. Reason: Correction

                          Comment


                            #14
                            Re: Blown cap on old dwell gauge - kal equip 2851

                            but is it blown, or just got hot enough to burn the paint??
                            thats the reason to test it

                            Comment


                              #15
                              Re: Blown cap on old dwell gauge - kal equip 2851

                              Check it with an ohm meter. If you need a new one the color bands are a key to its value.

                              Comment


                                #16
                                Re: Blown cap on old dwell gauge - kal equip 2851

                                Where does this red wire go? It mistakenly got +12V power on it which is what smoked the resistor.
                                Attached Files

                                Comment


                                  #17
                                  Re: Blown cap on old dwell gauge - kal equip 2851

                                  Originally posted by redwire View Post
                                  Where does this red wire go? It mistakenly got +12V power on it which is what smoked the resistor.
                                  That goes to two AA batteries. Just FYI the other red wire in the pic goes to a 9v battery.

                                  Comment


                                    #18
                                    Re: Blown cap on old dwell gauge - kal equip 2851

                                    Um, how many batteries are in this? A pair of AA's and a 9V?
                                    Usually these run off the 12V power at coil(+) for tach, dwell. Maybe the battery is for small engines.
                                    Unless... this meter must have an ohmmeter function? That would explain the smoke lol.

                                    I would measure the burnt resistor value and see if its good for a guess at what it was or its dead. For ohms function (slide switch to the right?). One leg of the burnt resistor connects to GND.

                                    The small transistor is the inductive pickup amp and although nearby it is not a suspect.

                                    Comment


                                      #19
                                      Re: Blown cap on old dwell gauge - kal equip 2851

                                      Originally posted by redwire View Post
                                      Um, how many batteries are in this? A pair of AA's and a 9V?
                                      Yes indeed. Three batteries total. I would kill for a set of instructions to know why haha.

                                      Originally posted by redwire View Post
                                      Usually these run off the 12V power at coil(+) for tach, dwell. Maybe the battery is for small engines.
                                      Unless... this meter must have an ohmmeter function? That would explain the smoke lol.
                                      It does have this function! I probably should have put all of the functions in the title. Attached is a pic of the front. It does dwell, tach, volts and ohms.

                                      Originally posted by redwire View Post
                                      I would measure the burnt resistor value and see if its good for a guess at what it was or its dead.
                                      Ok that will be my next task. I think I found a few good youtube tutorials.

                                      Originally posted by redwire View Post
                                      For ohms function (slide switch to the right?).
                                      Precisely! Volts/ohms. The other switch is for tach/dwell.
                                      Attached Files

                                      Comment


                                        #20
                                        Re: Blown cap on old dwell gauge - kal equip 2851

                                        Did you try to see if it would work? Volts and ohms are easy to check. For tack and dwell you would need an old car with points.

                                        Comment

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