Trying to repair a bigscreen TV

Discussion in 'Technical Repair' started by strantor, Jun 21, 2011.

  1. strantor

    Thread Starter AAC Fanatic!

    Oct 3, 2010
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    Good morning/day/night my international friends. I have scored another free broken TV (the one on the right). The one on the left was my first and it was beyond repair, gave up on it. This new one is only 4 years old and looks much less broken. I have no experience (other than my previous failure) repairing TVs. I thought maybe you all could take a look at the pics and let me know what I'm up against.
    [​IMG]

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    The way that all 3 color tubes project the image with the same warp in the middle makes me think that there's a problem with the screen itself or the mirror behind. I took out the mirror and its a metal frame with reflective mylar stretched over it, like an airplane wing. I couldn't see any warp in it, but it may be too miniscule to see with the naked eye. what do you think?
     
  2. Jotto

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    Apr 1, 2011
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    First you need to do the convergence alignment. This is not easy and you will need a pattern generator.

    You might have a built in display that might work, not sure about what model it is.
     
  3. strantor

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    NOOO! I want this to be easy! crap. Other than a pattern generator (don't know what that is, but I'll look it up), what will I need to do the alignment? Is it a mechanical adjustment? does it require 2 people? As for the model, I will have to get back to you on that. All I know right now is that it's a JVC 52" widescreen projector HDTV, made in '07.
     
  4. debe

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    Sep 21, 2010
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    A patern generator for convergence puts a crosshatch on the screen of vert & horz lines, The idea is to adjust the red, green & blue tubes to get them to form one line not 3 different ones like is in your picture. Some sets have a function that gives a vertical line & a horizontal line to set up the tubes. The convergence can be either electronic or mechanical adjustments, or both.
     
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  5. PackratKing

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    Analog TV.
    All alignment hardware is housed in rings around the CRT yoke.
    If the set was fancy enough, color, dot and crosshatch alignments on the raster are done by shifting rings w/ tiny magnets around the yoke assembly. An NTSC ? dot/crosshatch/colorbar/tone generator for alignment features is necessary. For field work, I had these on a vcr tape sooner than lug the gen. around.
    Lesser sets had very few easy electrical adjustments.

    ** All has to be done w/ the set up and running, please be careful.

    Being you are dealing with three separate color guns, the adjustment is likely in the mount hardware as a sort of gimbal arrangement, with guns mounted on sprung pivots.
    The set may have a feature that projects a small "X" from each gun somewhere on the screen for convergence, so you don't go blind trying to see the whole picture in a mirror.
    Not familiar with actual screen construction, I would think your screen had to be dead flat to focus right.
    Some of the earlier rear-projection units have a large fresnel lens [ packrat priceless ] for uniform brightness or limiting viewing angle.

    I have yet to mess with anything digital, hope this is some help :rolleyes:
     
    Last edited: Jun 21, 2011
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  6. strantor

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    is the bowed/warped appearance also due to the convergence issue? or are we looking at 2 seperate issues, convergence and warping? Some other info I have googled (information not pertaining to my specific set) suggests that when convergence ICs go bad you can get this warping effect, but from what I can tell there are 3 different ICs for red, blue, and green. I find it hard to believe that 3 seperate ICs are exhibiting the same warp effect which is why I suspect a warped mirror. I also hypothesize that a warped mirror could cause a misconvergence. Am I barking up the wrong tree with the mirror?
     
  7. beenthere

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  8. R!f@@

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    You have to ask ur self one thing before jumping
     
  9. Jotto

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    First thing to fix is convergence, you don't fix that there is no reason to continue any further. Being a projection tv, three tubes. Very easy to mess up convergence moving the set or being dropped when moved. Yokes very seldom go out of convergence. You are going to need something for a pattern generator, this will be best if you have white dots all across the screen so the alignment will be better. It would be nice to have a cross hatch pattern to see which tube is correctly positioned, then align the other two to that one.

    Pincushion is a minor problem that should be corrected after you complete the convergence problem.
     
  10. R!f@@

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    Did the TV came out that way ?
    I presume some one else must have tried to re align the set before, so why do you think you can do it?
     
    Last edited: Jun 21, 2011
  11. #12

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    Nov 30, 2010
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    Dot/bar/crosshatch generators are a lot smaller nowadays. I saw one that runs on a 9v battery and fits in your shirt pocket about a decade ago. It cost over $100 then, but they are probably cheaper now.

    Some of these TV's have the pattern generator in the software. The trick is to get the service manual so you know how to get into the menus. Strange stuff like, unplug it and press brightness and contrast while you plug it in. Be careful not to adjust the horizontal frequency off the end of its range of the TV will never start again. Lots to learn!

    I vote for mechanical problem with the 3 tube mounting, but I am way over my head making a statement like that. I watch with curiosity.
     
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  12. Jotto

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    I use the VP401, also have the CM2125, both are sencore. I have never used the CM2125, I wouldn't have purchased the CM2125, the VP401 is portable does much more, and is easy to operate.

    Convergence when its first done at the factory is done with a microscope. They will use either small white dots or a square with colors all across the screen. I am going to see if I can take some pictures in the morning to show what convergence might look like if its programmed into the television. I would expect this one to have it since it is fairly new and they started putting these patterns in quite a while ago for the technicians.
     
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  13. debe

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    This is a DVD i made for checking TVs & monitors for convergence, recorded from TV station.
     
  14. debe

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    This is a cross hatch/dot generator i built about 20yrs ago.
     
  15. strantor

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    I've got 3 things going for me:
    #1. I'm more determined than the last guy
    #2. I live in America, steeped in the "throw-away mentality". Folks around here don't believe in fixing things very much anymore. They want new & shiny.
    #3. I don't have anything to lose. I don't have anything invested in the TV so I'll try anything.

    I did find evidence that someone had been inside the set, but who? The owner, who likely pushes papers? It's very possible that no electronically competent person has set foot on these shores.
     
  16. strantor

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    That's cool!
     
  17. PackratKing

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  18. strantor

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    So, I got the model# off my set, HD52W59 and google that + the keyword Convergence and came up with this. A fuse. All it was was a fuse. Took me a while to find it because it didn't look like a fuse; it was a permanent type I had to desolder. I replaced it with a fuse holder on wire leads from radio shack. 6$ for the holder + fuse. Picture looks almost perfect.

    [​IMG]


    Ok, so at this point, everything's good. just a very minimal convergence problem. I went in the menu to auto convergence adjustment. The TV said that it would take about 1 minute to complete and not to touch any buttons. I started and saw quick flashes of red all over, but lost interest and walked away. When I came back 5 min later, the TV was off. it wouldn't turn on. I unplugged it and re-plugged it and turned it on. When it came up, it was a black screen with a blue and a green horizontal line, then it turned off by itself, then turned itself back on - and did this 3 times before shutting off for good again. I went throught this sequence 3 times. I unplugged it and left it overnight. In the morning, I plugged it back in, and we're back to square1. Same exact pincusion picture as before. I guess the fuse went out again, but why did doing the auto convergence adjustment cause the fuse to blow? Should I replace all the resistors around it?
     
  19. PackratKing

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    Should you also have a red line in the black [raster] ?

    What do you have to hook up for a signal source........broadcast / cable / satellite / vcr ?? I ask this 'cuz the menu in your good picture is only an onboard feature of the unit, and comes up briefly when called for...........or does it have to be dismissed with an "OK" to a selected function ?

    How about the obvious stuff.........board-to-board jumpers w/ burnt or corroded / tarnished pins -- cold solder anywhere, scorched pcb's, or component parts.........detritus on pcb's or someone elses attempts at soldering leaving tiny solder particles shorting chip legs ??
    All that common annoying stuff you've likely already looked for........:D please forgive if that is the case.

    following this.........................
     
    Last edited: Jun 22, 2011
  20. strantor

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    I would think so. Maybe it was there, but I didn't see it. I don't think it was there though.

    Yes, i was only using the menu. When I get home, I will replace the fuse and hook cable or a DVD up to it. I was thinking, to emulate the crosshatch that you guys gave me, I might just draw a crosshatch image in MSPaint and hook my laptop up to it.
    The entire inside of the set is extremely dusty, dust caked thick in some areas. I am going in there with a can of compressed air and clean it all out. While I'm at it, I will inspect everything for all the issues you mentioned. go over it with a fine toothed comb. I should have done that first I guess, but I was eager to see a pretty picture on the front side.

    Thanks
     
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