HAIER 17¨ CRT monitor image shaking

Discussion in 'General Electronics Chat' started by elpillo0807, Sep 2, 2014.

  1. elpillo0807

    Thread Starter New Member

    Sep 2, 2014
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    Hi! I´m new in town and want to say thanks to all of the people that take his time to help the others!

    I have a 17" CRT monitor branded as Haier (el chapo, I think) tha was working fine, but from a few days on the image starts to shake horizontally (i think) so the monitor is almost imposible to be read, even the "NO SIGNAL" banner is shaking so I think it has to be something inside the monitor.

    I´ve surfing the web and found a reference about something called ´X-mas tree effect´ but no other reference or explanation about how to solve it.

    so I need any clue about how to solve this problem or at least where I can look inside the monitor or what component I must check

    many thanks in advance

    SAMH
     
  2. ISB123

    Well-Known Member

    May 21, 2014
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    Don't even try to open that thing up,it can kill you! EM can cause the shaking so if you placed something with high EM emission near by it could cause the problems.
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,000
    3,229
    A filter capacitor failure in the power supply could cause excessive ripple the could cause the observed jitter.
     
  4. elpillo0807

    Thread Starter New Member

    Sep 2, 2014
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    Many thanks
    I will check the capacitors, in fact the monitor is no close to any EM emitter.

    the image just moves conyinuosly from one side to the other of the screen, and the borders (left and rigth) are moving forming a pattern that resembles the leafs of a xmas tree
     
  5. MrChips

    Moderator

    Oct 2, 2009
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    Can you post a photo of the screen?
     
  6. #12

    Expert

    Nov 30, 2010
    16,261
    6,770
    My mind goes to the horizontal deflection system where an arc in the high voltage can disturb the synchronization.

    If you open it, use your human senses first. An arc can choose you as the ground path!
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
    2,369
    Another cause of horizontal jitter is weak Horiz sync OR the horiz hold slightly at one end making it hard for the sync to pull it back in.
    Try adjusting the H. sync if it has one.
    Max.
     
  8. elpillo0807

    Thread Starter New Member

    Sep 2, 2014
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    Thanks to everybody, I will try to post a picture as soon as possible, yesterday nigth I changed the main capacitor in the power supply and three other ones around it, but no changes in the image.

    I will check the H-Sync adjustment, but how cqan I check if there is any arcing in the high voltage area, the monitor is dissasembled on the my reparations desk.
     
  9. #12

    Expert

    Nov 30, 2010
    16,261
    6,770
    To check for arcing, open the case, turn the monitor on, put both hands in your back pockets. Look for arcs. Smell for ozone. Watch for smoke. It might help to darken the room a bit.
     
  10. elpillo0807

    Thread Starter New Member

    Sep 2, 2014
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    The PCB has the following numbers on it:

    LK-29 94V-0 E78613

    is there any choice of get an schematic or diagram of it??
     
  11. BR-549

    Well-Known Member

    Sep 22, 2013
    1,981
    388
    Take the unit to a quiet area. Turn the lights off. Be wery quiet. Turn unit on. Look and listen.
     
  12. elpillo0807

    Thread Starter New Member

    Sep 2, 2014
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    I see now that the model is Haier 1772EH

    any idea of where can I get the servcie maual, diagram or schematics

    Many thanks,

    SAMH
     
  13. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    My first thought is dry joints (Dodgy RoHS solder) maybe on the divider that taps a sample off a flyback winding for the phase comparator in the sync chip - arcing there could cause horizontal shakes - or more likely line tearing.

    Some CRT monitors have a sync winding on the flyback transforme to keep the main SMPSU in step, another place to check for anything loose.

    The only other springs to mind is a degauss fault, that can make the picture quiver - but not just horizontally. There's usually a rainbow colour distortion too.

    The degauss component is a PTC thermistor that conducts a large AC current into a coil round the CRT that decays as the current heats the PTC - the residual current to keep the PTC hot is enough to wobble the picture, so a time delayed relay switches it out by the time the CRT heater warms up.
     
  14. elpillo0807

    Thread Starter New Member

    Sep 2, 2014
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  15. ian field

    Distinguished Member

    Oct 27, 2012
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    Hard to see - but it doesn't look so bad on the LHS. The scan deflection starts from the centre of the screen and progresses to the RHS - that is the horizontal forward conduction period, at the RHS; the transistor lets go and the energy stored in the flyback inductor produces the rapid retrace to the LHS and also generates the EHT.

    My best guess would be a dodgy solder joint not far from the horizontal scan transistor.

    Some of the classier 17" monitors had separate scan and EHT transformers - so possibly twice as much ground to cover!
     
  16. elpillo0807

    Thread Starter New Member

    Sep 2, 2014
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    the effect i shown in both sides of the image, the angle of the shoot wasn´t the best. I will check all the solders around

    many thanks
     
  17. MaxHeadRoom

    Expert

    Jul 18, 2013
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    It does look like corona discharge could also be causing it, as suggested by others, look and listen in the back in darkened room.
    Max.
     
  18. wayneh

    Expert

    Sep 9, 2010
    12,100
    3,034
    A bad cable or video board can give give a similar appearance. Have you ruled those out?
     
  19. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782

    When I serviced monitors for a living, I frequently encountered intermittent VGA cables. They give out where they get bent most; next to the plug and next to the stain relief bushing at the back of the monitor.

    If you test with a DMM or continuity checker, its impossible to guarantee there won't be callbacks for further intermittents - I test with a 12V SLA battery and one filament of a H4 headlamp bulb to limit the current, if one of the wires is about to fail - that makes sure it does while you're there to do something about it.

    Chances of getting a replacement VGA cable for any particular CRT monitor these days is probably slim. One option is to buy a cable for a monitor that has a socket on the back, you can cut one of the plugs of and splice it inside the monitor case, the other option is to carve away the moulded plug body and cut the cable back to where it isn't dodgy, you can get 9/15 sub-D housings that clamp together with screws.

    If you can't salvage the plug header, you can buy just that bit, but some VGA cards have one hole blanked on the socket - you can wiggle the unwanted pin till it snaps off (at risk of bending surrounding pins). The method I use is to make sure I've got the right pin and grip it with pointy-nosed pliers while heating the solder receptacle on the other side, as the plastic starts to melt the pin pulls out easy.
     
  20. elpillo0807

    Thread Starter New Member

    Sep 2, 2014
    8
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    Many thanks, I will change the VGA cable because fortunately I have another monitor of the same model whose flyback melted a few months ago, I have almost all the spare parts that I could need!
     
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