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Shredder very slow to start

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    Shredder very slow to start

    Hi Folks

    I have a shredder, the problem is after putting the paper it takes about a minute for the motor to start and shred.

    I trouble shooted a lot and figured out that the problem is the voltage at the coil end of the relay is taking time to reach 24V. It rises very gradually and as soon as it reaches 20V the motor starts.

    The question is what component could be causing this ? Could caps be the problem. Please see PCB images below

    Attached Files

    #2
    Re: Shredder very slow to start

    try new solder on those bad joints .
    if that doesn't fix it then you may as well change all 3 electrolytic capacitors .
    if that hasn't worked change relay driver transistor
    Last edited by petehall347; 11-06-2019, 11:10 AM.

    Comment


      #3
      Re: Shredder very slow to start

      Also check that the gears etc. are not full of paper dust and causing things not to operate, Check the motor to make sure it is turning freely and that the bearings are not causing the fault.

      Comment


        #4
        Re: Shredder very slow to start

        Thanks. This is a new shredder and not used much so no issue with gears. I have ordered the replacement CAPS. will replace those and update once done. Thanks folks

        Comment


          #5
          Re: Shredder very slow to start

          Other possibility is that one of the resistors went open or one of the tracks broke. Some of the tracks on the bottom looks corroded or something weird is going on with them ... could they be to blame?

          Comment


            #6
            Re: Shredder very slow to start

            I see some crappy solder joints too.
            Attached Files
            Never stop learning
            Basic LCD TV and Monitor troubleshooting guides.
            http://www.badcaps.net/forum/showthr...956#post305956

            Voltage Regulator (LDO) testing:
            http://www.badcaps.net/forum/showthr...999#post300999

            Inverter testing using old CFL:
            http://www.badcaps.net/forum/showthr...er+testing+cfl

            Tear down pictures : Hit the ">" Show Albums and stories" on the left side
            http://s807.photobucket.com/user/budm/library/

            TV Factory reset codes listing:
            http://www.badcaps.net/forum/showthread.php?t=24809

            Comment


              #7
              Re: Shredder very slow to start

              Hi Folks

              I have replaced the caps with new ones. and resoldered some of the joints showing poor solder. But still the same problem, infact replacing the capacitors seems to make it worse. Now the voltage across the coil of the relay is stuck at 10V. i believe it has to reach 24 volts for the relay to trigger. What else could be the problem ?

              I looked at the transistor. All that written on it is A44 B331. Cant find the data sheet for this transistor. Is there an equivalent you are aware off.

              Some voltages i have recorded
              - Voltage at the receiver end of the IR recerive when path is blocked : 2.5V
              - Voltage at Base of Transistor (pin 2) : 1 V
              - Voltage between C and E (Pin 1 and 3) : 30V
              - Voltage across coil of relay : 8v (This should be around 24) but this is gradually very gradually increasing and climbing upwards
              Last edited by jinu_j; 11-09-2019, 07:07 AM.

              Comment


                #8
                Re: Shredder very slow to start

                I'd also make sure the paper sensor is actually working properly too...

                Comment


                  #9
                  Re: Shredder very slow to start

                  Paper sensor is working fine. Without the paper blocking the path between the sensors i see volts 0.5v and when i put the paper the voltage rises to 2.5V

                  Comment


                    #10
                    Re: Shredder very slow to start

                    what's the reference point of base of transistor when you say 1V ?

                    Comment


                      #11
                      Re: Shredder very slow to start

                      transistor looks duff . try shorting emitter to collector and see if relay clicks in .

                      Comment


                        #12
                        Re: Shredder very slow to start

                        Originally posted by eccerr0r View Post
                        what's the reference point of base of transistor when you say 1V ?
                        The problem is i cant find the specs on the Transistor. It is just numbered as A44 B331.

                        I think its ground. Please see image below. The voltages measured are:

                        - Voltage at the receiver end of the IR receiver when path between IR Transmitter and receiver is blocked (Points C and D : 2.5V
                        - Voltage at Base of Transistor (pin 2) Points C and H : 1 V
                        - Voltage between C and E (Pin 1 and 3)Points G and I : 30V
                        - Voltage across coil of relay Points E and F : 8v (This should be around 24) but this is gradually very gradually increasing and climbing upwards
                        - Points A and B are points to the IR Tranmitter - 1V
                        - The transistor is at points G, H, I

                        Attached Files

                        Comment


                          #13
                          Re: Shredder very slow to start

                          Originally posted by petehall347 View Post
                          transistor looks duff . try shorting emitter to collector and see if relay clicks in .
                          Actually it did. When i shorted the Emitter and collector the Shredder started working. Thanks a lot.

                          So can i assume the transistor is bad and needs replacement. If so the problem is i cant find the replacement of a transistor with the name A44 B331 is there an equivalent.

                          Comment


                            #14
                            Re: Shredder very slow to start

                            This could be it. Either the transistor is bad OR the base is not being turned on enough.
                            Attached Files
                            Last edited by R_J; 11-09-2019, 11:43 AM.

                            Comment


                              #15
                              Re: Shredder very slow to start

                              Originally posted by R_J View Post
                              This could be it. Either the transistor is bad OR the base is not being turned on enough.
                              Is there anyway i can test for the second issue (base not being turned on enough) ?

                              Comment


                                #16
                                Re: Shredder very slow to start

                                Check the voltage between emitter and base. It should be around 0.7 volts or a bit more, also what is the voltage across C2
                                Last edited by R_J; 11-09-2019, 11:50 AM.

                                Comment


                                  #17
                                  Re: Shredder very slow to start

                                  Originally posted by R_J View Post
                                  Check the voltage between emitter and base. It should be around 0.7 volts or a bit more, also what is the voltage across C2
                                  The voltage between the Emitter and base is 0.45V

                                  Comment


                                    #18
                                    Re: Shredder very slow to start

                                    That seems too low to turn on the transistor, check the voltage across C2 (or R6) also check R7 10k, it could be open
                                    Check that the trace that goes from R9 to D5 to R6 to ZD1 is not open, this is the ground or common point
                                    C1+ seems to be the low voltage supply (5V?) It then goes through R5, through D6 to C2+
                                    Last edited by R_J; 11-09-2019, 12:19 PM.

                                    Comment


                                      #19
                                      Re: Shredder very slow to start

                                      Voltage across C2 is 1.8V. R7 is 10k and is not open. That would indicate a a problem with the diode D5? If I check the voltage between points after R7 and before D5 it about 1V, but i move it to after D5, it drops to 0.45V

                                      Comment


                                        #20
                                        Re: Shredder very slow to start

                                        D5 has nothing to do with the base circuit, it connects the emitter of Q1 to ground.
                                        Check the voltage across C1. C1 negative is the ground of this circuit.
                                        There are 2 wires next to the relay (Violet and Grey) where do they connect? The violet wire connects to ground, and the grey wire seems to control the voltage going to the Q1 base
                                        Last edited by R_J; 11-09-2019, 12:27 PM.

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