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Picture Tube Hazards

Discussion in 'Electronic Repair' started by Scott, Aug 20, 2007.

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  1. Scott

    Scott Guest

    I have a TV/DVD/VCR combo. The DVD player started skipping and just
    totally went out. I suspect that the lens is dirty but in order to clean
    it I have to remove the DVD unit from the TV. There are a couple of
    screws right below the picture tube that are going to be hard to reach.
    My question is it ok if I touch the bottom of the tube and not get
    electrocuted. I know about the hazards of touching the thick wire on top
    of the tube but unsure about the tube itself.

    -ss
     
  2. Meat Plow

    Meat Plow Guest

    Just don't come close to the area around that "thick wire" and you should
    be ok. And watch the other circuitry, avoid using both hands if you can,
    make sure the thing isn't plugged in.
     
  3. JANA

    JANA Guest

    There are proper procedures to remove the DVD player section. It requires
    some disassembly. TV service tech's do this type of work all the time, and
    there are no hazards.

    You should NOT be messing around in your TV set. Your safest procedure is to
    give it out to a service shop that services TV sets, and have them do the
    work. This way, it will be responsibly performed, and there will not be any
    possible safety issues after assembly, and when you are using the unit.

    --

    JANA
    _____


    I have a TV/DVD/VCR combo. The DVD player started skipping and just
    totally went out. I suspect that the lens is dirty but in order to clean
    it I have to remove the DVD unit from the TV. There are a couple of
    screws right below the picture tube that are going to be hard to reach.
    My question is it ok if I touch the bottom of the tube and not get
    electrocuted. I know about the hazards of touching the thick wire on top
    of the tube but unsure about the tube itself.

    -ss
     
  4. Scott

    Scott Guest

    I know what you mean but then I will have to bring my heavy TV to the
    shop (which is even harder since I don't have a truck), possibly wait a
    few days in which I won't have a TV and then get charge an arm and a
    leg...just to have my lens clean! I think I'll take my chances. That's
    what I get for buying a TV/DVD/VCR combo.
     
  5. Arfa Daily

    Arfa Daily Guest

    To be honest, you are likely to be wasting your time getting to the lens to
    clean it, as this is highly unlikely to be your problem unless a) you live
    in a very smoky house, or b) you've recently had some dusty building work
    done. Unlike with a CD player, normal household dust tends not to deposit on
    the lens of a DVD deck, because of the extremely high rotational speed of
    the disc, compared to a CD deck. This causes a layer of air to be dragged
    round under the disc at high speed, which tends to keep the lens dust-free.
    From years of experience repairing DVD players, it is far more likely that
    you have a worn laser ( or possibly, but less likely ) a worn spindle motor.
    If the unit plays CDs without skipping, then you can be reasonably sure that
    it is a laser issue.

    Arfa
     
  6. Scott

    Scott Guest

    It started skipping when I was playing a CD. It has been exposed to a
    lot of smoke from people exhaling towards the TV. I'm prepare for the
    worst anyways, just in case the DVD unit is bad I already have the
    replacement # from Panasonic($110). So either way I have to pull the
    unit out.

    -ss
     
  7. jakdedert

    jakdedert Guest

    Maybe they're just living on borrowed time, but I've fixed a number of
    them by cleaning the lens. I'd say it was the smokey environment in my
    house, but at least a couple of them were second-hand from others.

    jak
     
  8. Arfa Daily

    Arfa Daily Guest

    You may be lucky then, and a clean of the lens might restore it - for a
    while at least, and assuming that it's not a computer-style IDE type drive.
    Cleaning never seems to help with these. Clean the lens with a cotton bud
    (Q-Tip) moistened with electronics grade (99.7% + ) isopropyl alcohol.
    Polish with a dry cotton bud. Don't be tempted to adjust any pots mounted on
    the laser. Mis-adjustment of them is likely to result in rapid destruction
    of the laser diode(s).

    If the price you have from Pan is for just a laser, rather than a
    pre-assembled sub deck, be aware that most Pan DVD players, require
    mechanical adjustment of the tilt and skew after the laser is fitted.
    Provided that the model in question has the jitter meter software built in,
    this is not difficult, if a little fiddly.

    Arfa
     
  9. James Sweet

    James Sweet Guest

    Yeah you'll be fine. Take care not to damage the delicate neck and connector
    pins of the picture tube, if you crack the glass and let air in, the tube is
    toast.
     
  10. Scott

    Scott Guest

    Thanks for all the info! It has a IDE connector on the back so I'm
    assuming it's IDE. Also the price from Panasonic is for the whole unit.
     
  11. Arfa Daily

    Arfa Daily Guest

    Yeah, I kinda suspected that might be the case, which is why I made the
    comment. In that case, I think, from experience, that you are unlikely to
    recover it with cleaning. As these drives are pretty much totally enclosed,
    anything like cigarette smoke has a tendency to condense out on the outside
    of the drive, rather than on internal components. I think that in the end,
    you will finish up replacing the whole drive, as you felt that you might
    have to.

    Arfa
     

  12. Well if it is IDE could he just purchase a cheap computer DVD drive and put
    it in there? I'd try that, but I have no expierence with dvd players that
    use IDE drives and don't know if it would work.

    Mike
     
  13. Arfa Daily

    Arfa Daily Guest

    Hi Mike. I only ever tried it once. I can't remember the make, but I seem to
    think that it might have be a Sammy or a Tosh. Anyway, whichever, it didn't
    work. I remember asking the technical boys at whichever it was, why it
    didn't work, and they said it was a software thing. That somehow the
    player's operating system could recognise a 'correct' drive. I guess all CD
    / DVD drives have some type of readable model designator and serial number
    as part of their own controller's software, so maybe the machine's OS was
    programmed to evaluate this, or maybe the drives were even an OEM version
    'customed' for recognition in these machines.

    On the other hand, some time ago, I did a Yamaha hard disc recorder where
    the drive had failed. Looked like a pretty much standard IDE drive. We
    contacted Yammy to get a price on a replacement drive, and after the guy
    finished laughing at our sharp intake of breath, he told us that to be
    honest, we could put any old drive of the same size in it, but preferably
    one of the same make as well. So we ordered one off a computer supplies
    company for about a fifth the cost, flung it in, and away it went, good as
    gold. So the short answer is, I really don't know. I would be a bit
    reluctant to say that it's worth a go, for fear of corrupting the machine's
    software. There have been many cases where people have tried to make
    machines multi-region or region-free, by following either half-arsed
    internet instructions, or Honest Harry's Mod Tips page in DVD Hackers'
    Weekly, and ended up with unrecoverable corupted software, rendering their
    pride and joy useless, and outside of warranty ...

    At the end of the day, 110 bucks is not the end of the world, and if I was
    the OP, I think that I would feel happiest just dropping in a manufacturer's
    official replacement part.

    Arfa
     
  14. JANA

    JANA Guest

    Another thought. There are Laser cleaning CD kits on the market. It has
    little brushes in the disk, and you can simply put a drop of the cleaner on
    to the brushes, that comes with it. Follow the instructions.

    Most of the time, in these units skipping is a warn laser.

    --

    JANA
    _____


    It started skipping when I was playing a CD. It has been exposed to a
    lot of smoke from people exhaling towards the TV. I'm prepare for the
    worst anyways, just in case the DVD unit is bad I already have the
    replacement # from Panasonic($110). So either way I have to pull the
    unit out.

    -ss
     
  15. Scott

    Scott Guest

    I tried that already with no success. I even tried compressed air. Also
    the player is only 1.5 years old. I've probably only play around 50
    DVD's and a few CD's during that time.
     
  16. Arfa Daily

    Arfa Daily Guest

    You are brave to recommend these !

    IMHO, if you want to do no good at all at best, and actually damage the
    laser at worst, use a cleaning disc with little brushes on it ... On several
    occasions, I have seen an otherwise good laser wrecked by the brush getting
    caught in the lens suspension, and tearing this off with the high rotational
    speed of a DVD. As I have said on many occasions, it is rare for DVD lasers
    to suffer from dust like CD lasers. Even on CD lasers, the cleaning discs do
    little good, as the brush bristles are deflected by the 'wall' around the
    lens periphery, which is a typical design shape of a CD laser's lens.

    Arfa
     
  17. Scott

    Scott Guest

    Don't tell me that:( But since a laser cleaning CD kit is a 'CD'
    wouldn't the DVD player use the rotational speed for a CD?
     
  18. bz

    bz Guest

    Not to mention the mess that the 15 psi on each square inch of the tube can
    make if you 'get lucky' and shatter the tube. Kind of like a grenade going
    off. It can throw glass for quite some distance.




    --
    bz 73 de N5BZ k

    please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
    infinite set.

    remove ch100-5 to avoid spam trap
     
  19. Arfa Daily

    Arfa Daily Guest

    Well, once it has determined that it *is* a CD, it might, but there are a
    couple of qualifiers here. Firstly, most DVD players assume a DVD first, so
    spin up to full speed in readiness for that. They only then slow back down
    to CD speed, once they've determined that the data streaming off the disc is
    CD audio, not DVD video and audio. Secondly, some DVD players run CDs at
    full speed also, much like a personal CD player runs the disc at high speed,
    when in anti-shock mode ( to keep the bit bucket full ). Thirdly, some
    players have a lot of trouble making any sense of a cleaning disc. I don't
    know whether this is an issue with the data contained on them, or whether
    it's an issue with the brushes whacking the lens on every rotation, and
    vibrating it about its correct focus point. Whatever it is anyway, some
    players just will not lock their spindle servos on these discs, and they
    just run at very high speed, totally out of control. At the end of the day,
    the only way to clean a laser lens, is 'properly' - that is by hand,
    carefully, with nothing more aggressive than electronics grade IPA. Even
    then, any improvement may be only marginal or temporary as, if dust on the
    lens was the primary cause of whatever problem was apparent, the chances are
    that there is also dust on the critical angle mirror and the face of the
    pickup photodiode array, both of which are internal components of the
    optical block ( laser ) that you can't get at to clean. And again, DVD
    lasers seldom collect dust on their lens, due to the blanket of air dragged
    round under the disc, by its high rotational speed.

    Arfa
     
  20. And those lens cleaning CDs/DVDs may do more harm than good.

    --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
    Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
    +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
    | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

    Important: Anything sent to the email address in the message header above is
    ignored unless my full name AND either lasers or electronics is included in the
    subject line. Or, you can contact me via the Feedback Form in the FAQs.
     
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