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New DVD laser moves but doesn't light

Discussion in 'Troubleshooting and Repair' started by MoDz, Sep 13, 2012.

  1. MoDz

    MoDz

    2
    0
    Sep 13, 2012
    Hi guys. I'm not sure if my question is for this forum, please take my excuses if it isn't.

    I am lame when it comes to electronics, but I'm trying to repair a DVD player's laser.
    I bought 2 laser heads (just in case) and they both have the same strange behavior - the laser doesn't light although everything moves properly. I bought another ribbon cable as well, but when it's being used, the same problem occurs. Both of the potentiometers, the one for CDs and the one for DVDs, are set at 3.5K ohms which should be fine, and I haven't touched them, first I want to find out why the laser isn't lighting.

    Here's a video showing the laser trying to read (I'm sorry for the poor quality, my phone doesn't have auto focus when recording videos) and here's a picture just in case that you don't know what is what on the video.

    Thanks!
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,137
    1,846
    Nov 17, 2011
    This sounds like the problem is not the laser (nor is it the cable) but the laser driver on the mainboard of the player.
    Are you sure you grabbed a DVD laser head? If you laid hands on a CD laser head you wouldn't see anything because it is in the infared.
     
  3. MoDz

    MoDz

    2
    0
    Sep 13, 2012
    Thanks.
    Yes, I bought the exact same laser as the original one - Sanyo SF-HD65. The player is Philips DVP5140 if it matters.
    The player had worked before I tried to repair it. It didn't want to read disks (but the laser lighted) and without a multimeter in hand I foolishly decided to tune those potentiometers a little. But it seemed I lowered the resistance too much and I blew the laser head. But these potentiometers shouldn't impact any other part of the player, should they?
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    9,137
    1,846
    Nov 17, 2011
    This I can't answer. It is unlikely, but not impossible. Can you get a repair manual for the player? A good one should tell you where to measure the Laser current and to what value it should be adjusted.
     
  5. Timescope

    Timescope

    43
    0
    Aug 30, 2012
    Some Lasers have a solder bridge for anti-static protection that has to be removed before use.
    Timescope
     
  6. Timescope

    Timescope

    43
    0
    Aug 30, 2012
    "The laser diode terminals between LD and GND are shorted with solder to protect the laser diode from electrostatic
    damage during transport and storage......Open the short lands promptly with a soldering iron after connecting the LD drive circuit."
    From the datasheet :
    http://www.datasheet4u.net/datasheet/S/F/-/SF-HD65_Sanyo.pdf.html.
    Timescope
     
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