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Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

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    Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

    Hi
    I have a Panasonic SAPM-31 mini hifi and the tape deck motor keeps spinning all the time
    If I just connect the ribbon cable to PCB That is connected to the motor, it spins continuously

    If I change the input it still spins

    I have put it all back together with all the belts in place and still
    I can play, forward and rewind but the motor never stops when I press stop

    This never used to happen so I am not sure if a transistor has failed or a diode
    I will really appreciate the help from this forum
    Thanks all

    Here is the service manual
    https://www.manualslib.com/manual/14...-Sa-Pm31p.html

    #2
    Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

    I suspect this is normal as the motor operates the mechanism when a button, ie Play is pressed. The motor runs in tape standby and when you hit IE(play) the plunger solenoid activates the mechanism, as there are no mechanical buttons to engage the mechanism.
    If you select CD, does the motor tape motor stop?
    Last edited by R_J; 04-11-2022, 02:18 PM.

    Comment


      #3
      Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

      Originally posted by R_J View Post
      I suspect this is normal as the motor operates the mechanism when a button, ie Play is pressed. If you select CD does the motor tape motor stop?
      Hi
      No it does not stop when selecting other modes
      I have been told it is not normal and this never used to happen to me before

      Comment


        #4
        Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

        Originally posted by lcdcaps1 View Post
        Hi
        No it does not stop when selecting other modes
        I have been told it is not normal and this never used to happen to me before
        Looking at the logic of Q1314 (page 61) the base should change from 1.9v to 0 volts in standby, this will change Q1314 collector from 10.1 to -0.1 volts
        But looking at the voltage on Q1316, it's collector only changes from 0.1 to 0, This suggests the motor - is always low (motor ON)
        Last edited by R_J; 04-11-2022, 03:06 PM.

        Comment


          #5
          Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

          Originally posted by R_J View Post
          Looking at the logic of Q1314 (page 61) the base should change from 1.9v to 0 volts in standby, this will change Q1314 collector from 10.1 to -0.1 volts
          But looking at the voltage on Q1316, it's collector only changes from 0.1 to 0, This suggests the motor - is always low (motor ON)
          The motor did not used to run continuously
          Not sure what's happened for it to start doing it now
          It doesn't stop when selecting other inputs Ask when stop js pressed it doesn't stop
          Something is up and not sure what
          I've read it could be a transistor
          Last edited by lcdcaps1; 04-11-2022, 03:16 PM.

          Comment


            #6
            Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

            After checking your voltages
            Pin 2 on c309 goes from 2v to 9v on startup and then steady 9v
            Q310 collector voltages on startup goes from 2v to 9v
            Q310 base has no voltage, when running
            When I keep my meter red probe on q310 base I get 1v for a blip and goes to mv

            Comment


              #7
              Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

              Q310 base is controlled by the logic from the microprocessor. 0 volts on Q310 base means that Q310 is not turned on, so the collector will be high. If you want, short pin2 of cn309 to ground and see if the motor turns off.

              These type of tape decks need the motor to be running so that when you press a function, the plunger engages the mechanism WHILE the MOTOR is running. If the motor is not running when you press play nothing will happen.

              Tape decks that have levers that you push to engage the mechanism keep the motor off until the mechanism is engaged. This is not how this mechanism works.
              The tape motor may turn off after 10min of non use. see if you don't play a tape and let it sit, maybe the microprocessor program will turn it off.
              Last edited by R_J; 04-11-2022, 05:14 PM.

              Comment


                #8
                Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

                Originally posted by R_J View Post
                Q310 base is controlled by the logic from the microprocessor. 0 volts on Q310 base means that Q310 is not turned on, so the collector will be high. If you want, short pin2 of cn309 to ground and see if the motor turns off.

                These type of tape decks need the motor to be running so that when you press a function, the plunger engages the mechanism WHILE the MOTOR is running. If the motor is not running when you press play nothing will happen.

                Tape decks that have levers that you push to engage the mechanism keep the motor off until the mechanism is engaged. This is not how this mechanism works.
                The tape motor may turn off after 10min of non use. see if you don't play a tape and let it sit, maybe the microprocessor program will turn it off.
                Thanks for the reply
                After looking at the schematic. I can see they state q309 as a plunger switch that works fine
                Also stated is q310 is a switch for motor
                As the motor is continously on I'm thinking q310 has failed..
                The microprocessor seems to be working as all the unit is working
                Radio.
                Cd
                And tape
                .if I short pin 2 to ground on cn309 and motor turns off does this mean q310 is faulty

                Comment


                  #9
                  Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

                  Q310 controls the motor circuit on the tape deck, if bypassing Q310 by shorting cn309/pin2 to ground turns off the motor, that means the circuit on the tape deck is working like it should, this does not mean that Q310 is defective.
                  You can also check the voltage on CN309/pin2 when you place the whole machine in standby, this should also turn off the cassette deck motor by turning on Q310 causing pin2 to go low

                  Comment


                    #10
                    Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

                    Originally posted by R_J View Post
                    Q310 controls the motor circuit on the tape deck, if bypassing Q310 by shorting cn309/pin2 to ground turns off the motor, that means the circuit on the tape deck is working like it should, this does not mean that Q310 is defective.
                    You can also check the voltage on CN309/pin2 when you place the whole machine in standby, this should also turn off the cassette deck motor by turning on Q310 causing pin2 to go low
                    Thanks I'll try this later .
                    If the motor does not turn off when shorting pin 2 to ground is q310 the culprit

                    Comment


                      #11
                      Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

                      Originally posted by lcdcaps1 View Post
                      Thanks I'll try this later .
                      If the motor does not turn off when shorting pin 2 to ground is q310 the culprit
                      No. then it is likely Q1316 shorted e~c or Q1314 is bad.

                      I have see other tape decks that use touch controls for there operation, and they keep the motor running, as that is what makes this type of mechanism work.
                      If the mechanism engaged before the motor started it would not have the power or momentum to engage the mechanism.

                      If the motor was not running, when you pressed PLAY there would need to be a delay for the motor to start and get up to speed before the plunger activated the mechanism to engage the tape heads/pinch rollers.

                      Comment


                        #12
                        Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

                        Thanks for the reply
                        But this was not happening before. So something is very funny
                        I'd expect the tape motor to stop when selecting another input
                        It does not make logical sense to always keep it running even when the radio is selected
                        I've never seen a transistor with this part number
                        B1GDCFGH0002
                        Do you know if there is an alternative please .thanks

                        Comment


                          #13
                          Can't find anything B1GDCFGH0002

                          Hi
                          I can't find information on B1GDCFGH0002
                          What would be a suitable replacement please thanks

                          Comment


                            #14
                            Re: Can't find anything B1GDCFGH0002

                            It's a transistor I'm guessing for a panasonic stereo
                            Cap Datasheet Depot: http://www.paullinebarger.net/DS/
                            ^If you have datasheets not listed PM me

                            Comment


                              #15
                              Re: Can't find anything B1GDCFGH0002

                              Originally posted by Uranium-235 View Post
                              It's a transistor I'm guessing for a panasonic stereo
                              Thanks but need a replacement
                              Do you know what is an alternative please
                              Thanks

                              Comment


                                #16
                                Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

                                They are sometimes refered to as digital transistors, they have internal base bias resistors, look at the number on the part itself.
                                Measure the internal resistors
                                Last edited by R_J; 04-11-2022, 08:58 PM.

                                Comment


                                  #17
                                  Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

                                  Originally posted by R_J View Post
                                  They are sometimes refered to as digital transistors, they have internal base bias resistors, look at the number on the part itself.
                                  Measure the internal resistors
                                  Thanks for the reply
                                  I'll have a look but can't read the writing on the part
                                  How would I know for sure if it is Q1316 or Q1314

                                  Comment


                                    #18
                                    Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

                                    Originally posted by R_J View Post
                                    They are sometimes refered to as digital transistors, they have internal base bias resistors, look at the number on the part itself.
                                    Measure the internal resistors
                                    Ok so after a lot of cleaning, I managed to get the writing on the transistor
                                    for B1GDCFGH0002
                                    The writing on the chip is
                                    33 07

                                    Can anyone tell me which transistor this is and what replacement will be fine
                                    Thanks

                                    Comment


                                      #19
                                      Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

                                      Originally posted by R_J View Post
                                      No. then it is likely Q1316 shorted e~c or Q1314 is bad.

                                      I have see other tape decks that use touch controls for there operation, and they keep the motor running, as that is what makes this type of mechanism work.
                                      If the mechanism engaged before the motor started it would not have the power or momentum to engage the mechanism.

                                      If the motor was not running, when you pressed PLAY there would need to be a delay for the motor to start and get up to speed before the plunger activated the mechanism to engage the tape heads/pinch rollers.
                                      So i measured the emitter and collector on Q1316
                                      i got 0.8 ohms

                                      so how do i know if Q1316 is bad and so is Q1314
                                      i can buy q1316 easily but q1314 is a pain as nothing is coming up

                                      Comment


                                        #20
                                        Re: Panasonic SAPM-31 Mini hifi, Tapedeck motor spinning all the time

                                        Originally posted by R_J View Post
                                        Q310 base is controlled by the logic from the microprocessor. 0 volts on Q310 base means that Q310 is not turned on, so the collector will be high. If you want, short pin2 of cn309 to ground and see if the motor turns off.

                                        These type of tape decks need the motor to be running so that when you press a function, the plunger engages the mechanism WHILE the MOTOR is running. If the motor is not running when you press play nothing will happen.

                                        Tape decks that have levers that you push to engage the mechanism keep the motor off until the mechanism is engaged. This is not how this mechanism works.
                                        The tape motor may turn off after 10min of non use. see if you don't play a tape and let it sit, maybe the microprocessor program will turn it off.


                                        i shorted pin 2 to ground on cn309
                                        the motor did not turn off

                                        Comment

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