Connect with us

A Sony' CRTs color is screwed up.

Discussion in 'Electronic Repair' started by micky, Jun 1, 2013.

  1. micky

    micky Guest

    I have a Sony 19" desktop tv, about 20 years old, which gave a perfect
    picture since I got it 10 years ago, until I went on vacation 10 days
    ago. I was gone for 8 days and when I got back the picture was weird.

    There are no ghosts but the colors are screwed up. OTOH a picture
    transmitted in black and white is pretty good, still black and white.

    But with a color picture, in some parts of the screen at least, the
    blue has become pure green and the red has become pure blue.

    A medium blue background has become all green except for a 2" red
    circle on the outer parts of the screen, and blue at the corners.
    Despite this, as a tv show progresses, there seems to be less red than
    normal, mostly some pink, and skin tones are all wrong. Probably
    everything is wrong.


    I was a moderately successful amateur repairman in the days of tubes,
    and I did some other repairs besides just changing tubes, but tv's
    have gotten a lot more complicated. Any chance I can fix this?

    Even if I can't, I'm curious what sort ol failure causes these
    symptoms?

    And would I have been better off leaving the tv on for 8 days, or
    putting it on a timer, than letting it sit that long. It seems to
    me that a lot of tvs and vcrs have failed when not used for months.

    Thanks.
     
  2. Sounds like a purity problem. Start by degaussing it.
     
  3. The laziest first step is try degaussing it, or make sure the degausser
    still works. Is the nasty thud and buss present when you fire up the
    set from being cold and off?

    It's been said lightning strikes can magnetize a TV chassis enough to mess
    up colors, but I have no first hand experience with that. TVs have so
    little metal even scrappers don't want them.

    A 19" television from 20 years ago won't have one of those north/south
    hemisphere detector chips, so it's probably not that thing.
     
  4. Smarty

    Smarty Guest

    A purity problem would NOT have black and white looking ok as reported in
    the original post nor would it result in explicit color replacements as
    reported.

    Sounds like a color demodulation problem.
     
  5. Phil Allison

    Phil Allison Guest

    "Smarty"
    ** The set is a 19 inch Sony - so it is a Trinitron type.

    I suspect the behaviour is typical of Triniton with a magnetised aperture
    grille. The degaussing thermistor may have failed in the set and at the
    instant of failure left with a parting blow by magnetising the grille.

    The OP can check for this by noting if the usual switch on " bong" noise
    still happens.

    He can also bring a magnet near ( not touching) the screen and see if that
    tends to fix various areas.


    ** Not likely.


    .... Phil
     
  6. Guest

    What Phil says. I did color tv repair for 20+ years, and it is
    amazing what magnetization can do. If there was a lightning storm
    while you were gone, that would explain a lot.
     
  7. Smarty

    Smarty Guest

    This is altogether surprising to me, but then again I virtually never
    did TV repair. I have a bit of trouble understanding why a magnetized
    shadow mask or aperture grill would still allow a black and white image
    to be correctly displayed. If beam alignment were 'spoiled' by residual
    magnetic contamination of the CRT near the faceplate or if the purity
    rings were not doing their job, then the outcome should be color
    blotches regardless of whether chroma saturation is absent or present. I
    hope this specific problem is eventually solved so I can hear the actual
    cause of the problem. This old dog loves to learn new tricks !
     
  8. John-Del

    John-Del Guest

    Not true. Purity problems are most apparent when the chroma is on. If one looks carefully, the purity problem does exist in the black and white image, but it's just no where near as apparent.
    A color demodulator problem would cause incorrect colors, but I've never seen one cause localized errors as the OP pointed out.

    Most likely the dual degaussing thermistor is either bad, or has one lead detached from the board.
     
  9. Phil Allison

    Phil Allison Guest

    "Smarty"
    "Phil Allison"
    ** I did - in the B&W days in Australia, circa 1972 and onto to 1976.

    But it never grabbed me.



    ** Once, I was optimistic enough to buy an "re-conditioned" ( = re-gunned )
    26 inch colour tube for my own TV. It was a regular, three stripe, full
    convergence, colour Toshiba CRT with removable yoke dating from the early
    1970s.

    The tube supplier wanted the old tube back so I had to have it out of the
    set and ready - the exchange took place around 11AM. I fitted the tube
    that afternoon and after a heck of a lot of work was able to watch my
    favourite TV programs the same evening.

    Doing a full convergence "ab initio" on an aging and rather heavy TV set is
    not for the faint hearted - but the set served me damn well for another 10
    years.

    Interesting that electron guns cathodes ( particularly the red one ) wear
    out long before phosphors on the tube face are history.



    ..... Phil
     
  10. Smarty

    Smarty Guest

    I have not dealt at all with magnetized Trinitrons / aperture grills,
    and only have very limited experience with magnetized conventional CRTs
    but purity problems certainly were visible in the black and white images
    of those needing degaussing. It did not take moving color images to
    suggest purity / magnetization nor did it take careful inspection. The
    other, even more confusing original post issue was the non stationary
    nature of the color shifts, and the fact they were reported as moving
    with the displayed image, again evidence that the problem was not a
    purity problem.

    I gladly defer to the experience and judgement of those who repair TVs.
    My experience is limited to building a Heathkit color set a million
    years ago and repairing my Advent and Kloss projectors, not using or
    needing any purity control whatsoever!
     
  11. Smarty

    Smarty Guest

    I recall vaguely that the rare earth material from which red phosphors
    were created was comparatively inefficient, unstable, and expensive. I
    think it might have been ytrium but I may have the name wrong. Zenith
    and others many decades ago proudly introduced newer and more advanced
    red phosphors but I would not be surprised that they wore out faster.
     
  12. "Smarty" wrote in message
    This broad error about red phosphors has been repeated many times in this
    group. Many people here grew up during the introduction of rare-earth
    phosphors, so it's hard t understand why the error persists.

    The original red phosphor had low output and turned orange-ish when pushed.
    The rare-earth red phosphor -- introduced in the mid-60s (I think) -- had
    greater output and more-consistent hue. It might have deteriorated faster (I
    don't know), but //it// was the advanced phosphor -- not the phosphor that
    preceded it.

    I specifically remember a radio program sponsored by Sylvania that promoted
    these new phosphors as bringing color TV "out of the dark ages".
     
  13. John-Del

    John-Del Guest


    Perhaps your experience is with the old delta gun arrangement, which were prone to more purity error and more severe error. But I can tell you that with modern in line arrangements (Sony being no exception), bad purity is not always obvious in black and white pictures.

    The

    I reread the OP's post several times, and don't see what you mean by non stationary color shift. From what I read, the purity error was static on thescreen. I'm not a betting man, but I'd bet that if the OP degausses the TV, the problem will go away.
     
  14. Smarty

    Smarty Guest

    Thanks John for the further clarifications. My experiences in this
    regard are so very limited that the only cases I have seen cause static,
    noticeable blotches, visible in black and white at least as much so as
    in color. They also do not agree with the OP comment: "As a tv show
    progresses, there seems to be less red", suggestion that the color error
    was not a static problem which (again in my very limited experience) is
    not the way a magnetic bias displays itself.

    For the very few situations I have personally dealt with where
    degaussing ***was*** the issue, such as after building a Heathkit from
    parts, or moving a TV from one room to another, the purity issue
    manifested itself the same, namely, static, highly visible blotches,
    both in the color and black and white displays. The black and white
    impurity effect, if anything, was much more obvious, owing to the
    masking and obscuring of color errors in a highly colorful program.
    (Same comment regarding convergence errors or for that matter most errors.)

    I entirely concede that this may be totally a color purity problem
    caused by magnetizing, and sincerely thank you and the group for
    enlightening me in this regard.
     
  15. Guest

    Even after the introduction of the rare-earth phosphors, the red
    phosphors were less efficient and the red electron gun still had to
    put out more electrons than the green or blue guns and so the red gun
    trended to poop out sooner than the green or blue guns.
     
  16. Guest

    Hats off to you for building one of those early color tvs. I hated to
    see Heathkits close up. Do you remember how they started with kits
    for airplane builders? The electronics came a little later. I still
    have some instruction manuals for some of their early kits that I
    built in the 1960s. Had my wife(to be) help me with reading some of
    the resistor color codes as I am partially RG colorblind
     
  17. Smarty

    Smarty Guest

    I do remember the original catalogs showing airplane related kits, but I
    did not get into it really until the late 1950s. I guess I became a
    Heathkit maniac. I built nearly 50 kits starting in the 1950s and ending
    in the 70s as I recall. The ham radio stuff was the earliest (DX20,
    DX40, Apache, SB-1 Single Sideband Adapter, SB101 transceiver, SB200
    kilowatt amplifier, Q multiplier, KW Compact mobile amplifier, SWR
    bridges, wattmeter, phone patch, two meter and UHF rigs,......), test
    equipment (scopes, signal generators, a couple VTVMs, a couple digital
    VOM / DMM meters / frequency counter, decade capacitor and resistor
    boxes,), all sorts of tube and then solid state audio equipment, a
    25inch color TV (for my parents), lots of electronic gadgets like
    digital clocks, indoor outdoor thermometer, digital platform scale, grid
    dip meter, "Cantenna", weather stations, and on and on.

    I am also saddened to see the era of electronic construction fade away.
    No doubt the deterioration of American leadership and expertise in
    "building things" is a bigger and related source of disappointment for
    those of us who remember this period fondly, and have deep concerns for
    our kids and grandchildren.

    The Heathkit appeal for me personally wore out as I began to do my own
    designs and finished my engineering program. I got heavily into digital,
    gave up ham radio (except for radioteletype RTTY), and began buying more
    advanced audio and video stuff. My basement in my parent's home looked
    like a cross between a wholesale electronics parts supplier and a messy
    teenager's bedroom.........

    Very little of it came with me when I got married and moved out. I
    presume my parents must have given most of it away except for the very
    few things I took with me. I still have one remaining Heath item only,
    an indoor outdoor digital thermometer, which I wound up modifying to
    control my hot tub water temperature nearly 30 years later!
     
  18. Guest

    What most likely happened here is that that the solder connections to the degaussing thermistor went bad and opened up on the initial surge after turnon.

    The idea is to magnetise one way and the other at less and less strength, evenually decaying to zero. What hapens in this failure mode is it gets magnetised one way, the connection breaks and the process is incomplete.

    Because of the high amperage involved there is usually a brown ring around the connection. To resolder you have to remove the old solder and clean the pin as well as the pad.

    The other possibility is the shadow mask (aperature grill in a Sony) cut loose. There is no fix for that, though I can do wonders with magnets around the bell of the CRT. The problem with that is that it might not be stable.
     
  19. I would also dispute that a black and white transmission
    I've been trying to reason this through. The best I can come up with is
    this...

    Whether purity is good or bad, the electron beams have to land /somewhere/. In
    a B&W image, it might not matter much if red winds up on blue, blue on green,
    and green on red. The result will be /something/ approximating a shade of
    gray.
     
  20. Guest

    It depends a bit on how well the phosphors' efficiency is matched. If the three cathode currents are pretty close, alot of people won't see much. I know what to look for though, and you need the right material to see it, alotof white. If the picture is too busy it is hard to see. Also, if the actual phosphor efficiency is not well matched, they compensated by making the less efficient phosphors larger.

    Also a magnetised CRT will exhibit some misconvergence, which is more visible on a high contrast image. You have to look hard though because the colorfringes will not be pure red, green or blue.

    But yes, in essence those electrons are going to hit somewhere.
     
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

-