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    Micromega CD player repair

    I was doing a ordinary change of a laser unit and mechanism on a Micromega stage CD-player. The laser unit is a Philips CDM12.4.
    After laser change, player refuse to play one single cd. Here is what happens:
    Tray closes. Laser succeeds focusing. Cd starts to spin, though way too fast,
    3 seconds later display shows "ERR".
    If closing tray without having a cd in, the display show "No disc" which means the laser can focus correctly and actually works, right?
    The CDM12.4 laser has an onboard RF amp, as can be seen in the picture.
    Before the laserchange the player actually worked, but had reading problems.
    Any advice is appreciated.

    Best regards
    PowerAmpFreak
    Attached Files

    #2
    Re: Micromega CD player repair

    disk spinning out of control is an unreadable signal.
    you can get this if the bias or gain on the laser is wrong.

    another symptom is the disk moving in small bursts & the laser lens clicking.

    Comment


      #3
      Re: Micromega CD player repair

      Thanks for fast reply, stj!
      There are no adjustments for gain or bias, only laser power which is set as the old pickup.
      The cd spins up maximum speed for 3-4 seconds, drops to near zero, and repeats again.
      I wonder what I can do to make it work..

      Comment


        #4
        Re: Micromega CD player repair

        scope the eye & look at the pot on the laser assembly.

        Comment


          #5
          Re: Micromega CD player repair

          and look at the caps in the psu, there may be ripple causing the laser to not read clearly.

          Comment


            #6
            Re: Micromega CD player repair

            Originally posted by stj
            scope the eye & look at the pot on the laser assembly.
            You mean scoping the RF amp data output, and watch for the "eye" pattern?
            What do you mean by "looking at the pot"?
            Didn't check for PSU ripple, but all +5VDC was nice and stable.

            Comment


              #7
              Re: Micromega CD player repair

              Does the laser emit?

              Most laser assemblies have a switch or a piece of flexible wiring which can be safely cut off (read the service manual first), to protect the laser diode from static.
              My first choice in quality Japanese electrolytics is Nippon Chemi-Con, which has been in business since 1931... the quality of electronics is dependent on the quality of the electrolytics.

              Comment


                #8
                Re: Micromega CD player repair

                Originally posted by japlytic
                Does the laser emit?

                Most laser assemblies have a switch or a piece of flexible wiring which can be safely cut off (read the service manual first), to protect the laser diode from static.
                Guess it's not possible to focus correctly if laser doesn't emit, right?
                The player can determine if there are a CD or not inside, which I assume is a result of focus ok...
                With no cd display show "No disc", with a disc inside it show "ERR".
                Other lasers I've replaced all did contain a solder jumper which must be desoldered (for ESD protection), but I can't see any on this dude.
                May be probably due to the RF amp fitted on the laser assembly itself, minimizing ESD problems, since laserdiode is "already connected" and properly terminated to the RF frontend.

                Comment


                  #9
                  Re: Micromega CD player repair

                  no, it may focus well enough to detect a disc, but not well enough to actually read it.
                  sigpic

                  (Insert witty quote here)

                  Comment


                    #10
                    Re: Micromega CD player repair

                    Originally posted by ratdude747
                    no, it may focus well enough to detect a disc, but not well enough to actually read it.
                    Yes, so the answer to the question "does the laser emit" must be YES since it's actually able to focus at all, though doesn't read it correctly, right?

                    Comment


                      #11
                      Re: Micromega CD player repair

                      The laser gives a decent 1V peak-peak RF signal measured right at the RF amp output. The "eye pattern" is visible but not that clear. If memory serves me right the eye pattern should be pretty sharp and clear. So could this mean the new laser is actually bad?

                      Comment


                        #12
                        Re: Micromega CD player repair

                        Believe it or not, but it appears my "new" laser was an old used one which the company where I ordered it, cannot explain. A new laser unit is on delivery!
                        Hope for better luck next time.

                        Comment


                          #13
                          Re: Micromega CD player repair

                          The new laser arrived, this time it was new and not used...
                          Unfortunately it didn't make any difference to the repair. It still shows "ERROR" in the display. There are just above 1V peak RF amplitude, and the "eye pattern" is visible. Have no idea why the player refuse...
                          There are no adjustments except for laser power which appears to be good since the RF level is ok. There are a few screws on the laser unit covered with glue so you shouldn't touch these.
                          Anyone having a hint?
                          Regards,
                          PowerAmpFreak

                          Comment


                            #14
                            Re: Micromega CD player repair

                            Checked the draw is closing and activating any relevant switches correctly.

                            Comment


                              #15
                              Re: Micromega CD player repair

                              yes, that seems fine, as soon as the tray enters "home" position, the laser unit begin to focus, cd starts to spin, but it speeds up too much, probably because it isn't able to read the disc properly (for any reason)...

                              Comment


                                #16
                                Re: Micromega CD player repair

                                Hi All,

                                I have the same issue for this case on my micromega player too. have anyone resolve this issue ? Thanks

                                Comment


                                  #17
                                  Re: Micromega CD player repair

                                  Hello everyone and health!!
                                  I understand, chtema old, but the answer to a question and have not found.
                                  I tried to attach four new CDM12,4. And always result one - ERROR. The eye moves as well as it is necessary by search, and the beam is not present, where that it vanishes. Where?

                                  Comment


                                    #18
                                    Re: Micromega CD player repair

                                    Could you please take a picture of the whole player ( without cover ) ?

                                    I might have an idea, but I am not sure it is the correct player I am remembering.

                                    Comment


                                      #19
                                      Re: Micromega CD player repair

                                      the eye pattern must be more that visible, it must be correct - it should look like perfect equal diamonds.

                                      Comment


                                        #20
                                        Re: Micromega CD player repair

                                        Originally posted by MViktor View Post
                                        Hello everyone and health!!
                                        I understand, chtema old, but the answer to a question and have not found.
                                        I tried to attach four new CDM12,4. And always result one - ERROR. The eye moves as well as it is necessary by search, and the beam is not present, where that it vanishes. Where?
                                        Check the mainboard. Close to where the laser FFC attach, is there a TDA1300T ?

                                        If yes, change it.

                                        Comment

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