Connect with us

TVs and speakers

Discussion in 'Electronic Repair' started by Sean O'Leathlobhair, May 27, 2004.

Scroll to continue with content
  1. I have come to this group since it seems to contain the most posts on
    this topic. Nonetheless, despite searching, I have not quite found
    the answer to my question.

    I have an 11 year old Sony TV. For most of its life it has had a pair
    of HiFi speakers two feet to either side. These used to be Mission
    707s but a couple of years ago they were replaced with bigger ones:
    Tanoy R7s.

    A few years ago (still the old speakers), the TV suffered some severe
    discolouration. This was similar to the effect described by others in
    this group: big green and purple patches. I guessed that it was
    related to the speaker magnets so I moved them away and waited. This
    did not seem to help and I considered bringing it into a shop to be
    checked. Luckily, I could not do this for several days and during
    these days the set corrected itself. The speakers had to go back to
    their original place but the problem did not immediately reoccur.

    In fact it was a long time (maybe more than a year) before the problem
    reoccurred but eventually it did. Now the problem is occurring more
    often (every few weeks) but also clears more quickly (hours).

    Previous threads on this subject say that the internal degaussing does
    not occur if the power is cycled with the remote control and suggest
    disconnecting the mains. How about using the power button on the set,
    is that enough? I don't normally disconnect the mains since unless I
    crawl behind the furniture to the multiway extension cable, I have to
    disconnect the extension cable and lose power to the video as well.
    Losing video power is annoying since it is too old to set its own
    clock. But if disconnecting from the mains were more effective than
    using the power button on the set, I would rearrange the cabling to
    make it easier.

    Now the question. Is this a sign that my TV is aging and will die
    soon? Or are the speakers to blame? Except in unusual circumstances,
    they do not move. The TV malfunctions are not linked to any equipment
    movements, they appear random but are becoming more frequent.

    I am considering replacing the TV but if the speakers are to blame
    then I may be in danger of ruining it as well. Are modern sets more
    resistant to magnetic fields? Are some models better than others? I
    cannot significantly rearrange the furniture so the TV will have to
    live with these speakers 2 feet away.

    Seán O'Leathlóbhair
     
  2. Jerry G.

    Jerry G. Guest

    The TV's degaussing will work each time the set is turned off for more than
    30 to 40 minutes. The degaussing coil should work each time the set's power
    is re-cycled. It does not matter if it is done with the remote, or the main
    power button on the set. The remote is controlling the same circuits as the
    power button. There is no difference in this set.

    If the speakers are closer than about 4 feet, they will re-magnetize the
    CRT mask all the time. Normally this is not going to do permanent damage to
    the CRT. It is only an annoyance.

    If you place the speakers far from the set and the degaussing is not
    working, it is possible you also have a fault in the degaussing circuit. The
    degauss thermo-resistor failing is usually the main cause of this circuit to
    not work. Other failures may be caused by cold solder connections, and or
    the degaussing coil itself may be defective (very rare).

    If the mask in the CRT is damaged from some type of disturbance, then the
    colour errors will not be able to be corrected. Usually the mask can go
    defective if the set was rough handled during transport, or if the set was
    dropped or knocked over. It is rare, but if one of the support wires in the
    CRT break or become out of position by themselves, there will be colour
    errors showing that cannot be corrected.


    --

    Jerry G.
    =====


    I have come to this group since it seems to contain the most posts on
    this topic. Nonetheless, despite searching, I have not quite found
    the answer to my question.

    I have an 11 year old Sony TV. For most of its life it has had a pair
    of HiFi speakers two feet to either side. These used to be Mission
    707s but a couple of years ago they were replaced with bigger ones:
    Tanoy R7s.

    A few years ago (still the old speakers), the TV suffered some severe
    discolouration. This was similar to the effect described by others in
    this group: big green and purple patches. I guessed that it was
    related to the speaker magnets so I moved them away and waited. This
    did not seem to help and I considered bringing it into a shop to be
    checked. Luckily, I could not do this for several days and during
    these days the set corrected itself. The speakers had to go back to
    their original place but the problem did not immediately reoccur.

    In fact it was a long time (maybe more than a year) before the problem
    reoccurred but eventually it did. Now the problem is occurring more
    often (every few weeks) but also clears more quickly (hours).

    Previous threads on this subject say that the internal degaussing does
    not occur if the power is cycled with the remote control and suggest
    disconnecting the mains. How about using the power button on the set,
    is that enough? I don't normally disconnect the mains since unless I
    crawl behind the furniture to the multiway extension cable, I have to
    disconnect the extension cable and lose power to the video as well.
    Losing video power is annoying since it is too old to set its own
    clock. But if disconnecting from the mains were more effective than
    using the power button on the set, I would rearrange the cabling to
    make it easier.

    Now the question. Is this a sign that my TV is aging and will die
    soon? Or are the speakers to blame? Except in unusual circumstances,
    they do not move. The TV malfunctions are not linked to any equipment
    movements, they appear random but are becoming more frequent.

    I am considering replacing the TV but if the speakers are to blame
    then I may be in danger of ruining it as well. Are modern sets more
    resistant to magnetic fields? Are some models better than others? I
    cannot significantly rearrange the furniture so the TV will have to
    live with these speakers 2 feet away.

    Seán O'Leathlóbhair
     
  3. Mike Berger

    Mike Berger Guest

    The effects of magnetic fields may be subtle and the color
    distortion may appear very gradually. Your degaussing coil
    should activate any time you turn the TV on, whether you use
    the remote or not, if it has been inactive long enough for the
    thermistor to cool down (20-30 minutes on most TV's). In
    other words, if you power cycle it 5 times in a row, it will
    only degauss the first time. Let it sit for 30 minutes and
    it should degauss again when you turn it on.

    Newer TV's aren't any better shielded, and yes, you can expect
    the problem to occur with a new TV. Many newer speakers are
    better shielded, however, so they can be placed near the TV
    in a home theater setup. You might want to consider getting new
    shielded speakers along with the new TV.
     
  4. That was not the answer that I was hoping for but thanks.

    I would be happy to replace the TV since it is very old and it would
    be nice to get a widescreen model. I am not keen to replace the
    speakers since they are quite new, sound nice, and cost more than the
    TV. Except for the possibility of being the cause of this problem, I
    am entirely happy with them.

    I had failed to guess that the home theatre problem was solved by
    shielding the speakers rather than the TV. I had hoped that it was
    the TV that was better shielded so that it could placed close to the
    speakers.

    I now have a tricky decision to make. For stylistic reasons, my wife
    would not accept the speakers moving further from the TV. Anyway, due
    to the size and shape of the room, moving them further apart would
    spoil the stereo effect since we sit only about 6 feet back from the
    TV.

    Suppose that the positioning must remain, is it best to leave the
    speakers in place when a problem occurs and attempt to degauss?
    Rather than move them away until the problem clears and then bring
    them back. My theory is that the TV should adjust with the expected
    fields present.

    You say that the problem would be likely to occur with a new TV. But
    would I be harming the new TV? If not, I could buy the new TV before
    the move that I just described.

    Longer term I may solve the problem in a different way. We may move
    the TV to another room. I had planned to move the HiFi with it.
    Maybe I will leave the HiFi where it is, dump the TV, and buy a small
    home theatre system for the other room.

    Just to confirm, is this the best possible degaussing strategy?

    1. Turn the set on and run it for a few minutes (is the time
    important?).

    2. Turn it off (anyhow) and wait 30 - 60 minutes. (I guess that if
    the run was short then this period could be short as well).

    3. Repeat the above until the problem clears.

    Seán O'Leathlóbhair
     
  5. Art

    Art Guest

    Many SONY Teles have a symptom that develops after a while where components
    in the degauss control and activation circuitry fail and need to be
    addressed. Inclusive are the thermistor and relay, if implemented in your
    set. Other possibility is if the set has been subjected to physical shock,
    aka being dropped or bounced, causing sustained damage to the internal
    components of the crt. May want to have a tech check it out for you for a
    securely definitive answer.
     
  6. Thanks.

    I don't know whether the degaussing works correctly when the speakers
    are removed. It is quite a while since I moved the speakers away and
    I do not recall details such as how long I waited between power
    cycles.

    It would seem that the mask is OK since the problem is not permanent.
    It would also seem that the degaussing is working since the problem
    does correct itself.

    The odd thing is that the problem is becoming more frequent. Do you
    know why that may be and whether there is a practical solution other
    than replacing the TV? Although the problem does not take long to
    correct, it is a nuisance since when it fails, my son takes over our
    bedroom which contains the only other TV.

    I used to do amateur TV repair but the last time I did, valves were
    still in common use. I still have a soldering iron, a multimetre and
    a fairly good theoretical knowledge of electronics but no experience
    of working on a modern electronic appliance. So only simple repairs
    (e.g. resoldering a poor connection) are feasible.

    If you see my response to Mike, you will see that I am considering
    replacing the set and later separating the TV and HiFi. If the
    speakers are not likely to cause permanent damage then I may buy the
    new TV in advance of the separation.

    Seán O'Leathlóbhair
     
  7. I am fairly sure that the set has not had any serious shock but is 11 years
    old so age is a candidate. The remote control has been well abused and it
    look like someone has been eating it. I guess that it was my son when he
    was younger. However, I don't think that abuse of the remote control is the
    cause of the problem.

    The trouble with getting it checked is that the minimum charge is a
    substantial proportion of the value of an old TV. A friend took his oldish
    but nice widescreen TV in for repair. The fault seemed to be an
    intermittent power supply fault and worth fixing. The shop tried and failed
    several times to fix it. The last I heard, he was discussing the cost of
    the non-repair.

    I could easily afford a new set but I don't like waste so if I can easily
    extend the life of this one, I will. Also, I don't know what to do with the
    old set. It is hard to even give them away. Charity (thrift) shops around
    here won't accept mains powered items and even the poorest of my friends
    already owns a better TV.
     

  8. I have one speaker of my stereo installation within a few inches of
    my TV (RCA CTC185 - 1999 model). The speakers don't bother the TV
    picture at all. I have an Aiwa shelf system with three-way speakers,
    which are magnetically shielded so the speaker magnets cannot affect
    the TV in any way.

    I live in a small apartment and, like yourself, I cannot rearrange
    my furniture (much, anyhow) either. Fortunately, as I said, even with
    my stereo speakers close to the TV, there is no color distortion.

    You will not ruin your TV with new stereo speakers. As others have
    said here, the problem could well be the auto-degaussing circuit in
    the television itself; if it is not operating, you will have color
    distortion from your speakers being so close to the set, as they are
    magnetizing the shadow mask. This, of course, always wrecks the
    purity. Note as well that if you try to degauss the CRT more than once
    every half-hour, the degaussing coils may actually work in reverse,
    that is, remagnetizing the shadow mask. (The instruction manual for my
    computer monitor cautions against this as well.)
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-