Tv turns off then instantly cuts off help please

Discussion in 'General Electronics Chat' started by rastaman46, Oct 30, 2014.

  1. rastaman46

    Thread Starter Member

    Nov 17, 2011
    69
    0
    Hi its me again

    My friend tv died today

    All it does is turn on but cuts off instantly

    I have power suply screen witch part can cause it can any one link me please.

    Thanks
    Kind regards
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,148
    3,058
    Is that upper right capacitor (EC8 ?) damaged or pulled off the board? It shouldn't look like that.

    Have you looked for a schematic?
     
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  3. rastaman46

    Thread Starter Member

    Nov 17, 2011
    69
    0
    Cap looks fine its just bent.

    Where i get schematics from?

    There no burn marks or anything like that.

    All id does is once back light kicks in tv cuts off

    Regards
     
  4. rastaman46

    Thread Starter Member

    Nov 17, 2011
    69
    0
    More if i turn on its never stops turning on and off just constantly doing this

    Mesuared voltages against prints on board all fine all matches up

    Regards
     
  5. ScottWang

    Moderator

    Aug 23, 2012
    4,855
    767
    If you check the capacitors then you should check their ESR using ESR meter, if you measure the voltage cross on the capacitor then you should using O'scope to see the ripple voltage, if you can see the ripple voltage then the capacitor was damaged.

    TVProblem_rastaman46_AAC.jpg
     
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  6. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
    1,190
    156
    Also look up problems with model number cause this isn't probably the first time this kind of tv has had this problem ...
     
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  7. rastaman46

    Thread Starter Member

    Nov 17, 2011
    69
    0
    Hi i dont have ESR meter all i have is standard meter
     
  8. rastaman46

    Thread Starter Member

    Nov 17, 2011
    69
    0
    I did google all i can bit did not find anything related to this power supply can it be firmware related
     
  9. MrAl

    Well-Known Member

    Jun 17, 2014
    2,439
    492
    Hi,

    Mine did the same thing, it was the low voltage power supply section, the electrolytic caps.

    Check the BOTTOM of the caps to see if there is anything leaking out, it may be brown or dark color and dried up already. You need a good flashlight and try to see UNDER the caps at least partially.
    Usually the top bulges too but if the bottom leaked it may not bulge.
    I had three bad ones and one good one, replaced all four. It works now.
     
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  10. rastaman46

    Thread Starter Member

    Nov 17, 2011
    69
    0
    Removed all caps mesuared all fine
     
  11. pwdixon

    Member

    Oct 11, 2012
    488
    56
    So what happened to what looks like a blown fuse in the lower left hand corner?
     
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  12. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
    1,190
    156
    Hey let try my luck and what's the model number of the tv ???
    What kind of TV is this ?? My times when the voltage is corrrect from the power supply there is a problem some where else .. But generally most issue start with the power supply and the Elec caps and the inverter boards and sometimes the caps on the main board...
     
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  13. rastaman46

    Thread Starter Member

    Nov 17, 2011
    69
    0
    Can it be eeprom?

    Tv is m
    Umc 39 really simple tv.
     
  14. wayneh

    Expert

    Sep 9, 2010
    12,148
    3,058
    Then the problem is likely elsewhere. A service manual would help.

    Is this a CRT? I don't see any high voltage components, like a flyback transformer for instance. Common failure. The power supply will shut itself down if it detects a fault. With an LCD, the backlight inverter is a typical failure.
     
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  15. wayneh

    Expert

    Sep 9, 2010
    12,148
    3,058
    I recently worked on a power supply. Some of its capacitors appeared to have decent capacitance (I can only take approximate readings with my meter). But using a DIY ESR I built showed that some had a very high ESR, 40Ω versus 1Ω for their new replacements.

    My point: You can't judge a capacitor without an ESR meter.
     
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  16. Gdrumm

    Distinguished Member

    Aug 29, 2008
    684
    36
    Fuse.JPG On the left hand side of the picture, the fuse looks compromised.
    It appears to have been factory wrapped, and that wrap has melted away, or been cut away.
    Have you checked the fuse?
    Gary
     
    Last edited: Oct 31, 2014
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  17. ISB123

    Well-Known Member

    May 21, 2014
    1,239
    527
    Use continuity test to see if fuse is blown.
     
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  18. ScottWang

    Moderator

    Aug 23, 2012
    4,855
    767
    Before I bought the ESR meter that i only could measured the capacitance as you did, although the capacitance is right, but the internal resistance could be too high, because the Electrolytic liquid was lost a lot, so i had to unsolder the capacitor and replaced a new one to tried.
     
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  19. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    Probably a transformer with shorted turns on the backlight inverter - a firm called HR does pattern spares of this sort. They started off making replacement flyback transformers for CRT TVs - I've never had a dud from them.
     
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  20. bwilliams60

    Active Member

    Nov 18, 2012
    725
    90
    You said you measured all your voltages on the output side correct? if you have done this properly, you should have 24v, 12v, 5v and 3v supplies from this connector. The tv will vary by make and model. If these are okay, I suspect you have issues elsewhere. Do you have a backlight if you leave it on in a dark room or is that out as well
     
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