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JVC 32" Widescreen - Turning itself off/degaus issue??!!

Discussion in 'Televisions' started by MAD ANDY, May 4, 2005.

  1. MAD ANDY

    MAD ANDY
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    Hi all

    got a 32" JVC widescreen which is a good few years old now, yet still better spec'd than some new models out today! Anyway, its done us well over the years and I've often seen it degaus, but just lately it seems to be doing it a lot during the day, sometimes noticable, sometimes only the 'click' sound heard even though the picture doesnt reset, however lately its also started turning itself off :confused: and then goes into some sort of self-protect mode where the amber LED flashes next to the consistent red LED, and if you try to turn on too fast it wont until after a set period.

    Any help would be most appreciated as we were just about to move this into the kids playroom and invest in either a Toshiba 36ZP46P or Panasonic 42" Viera 50 model which are currently on offer with a free Panasonic Diga DVD recorder (favouring the Tosh as if I remember correctly the picture was far superior to the plasma) but dont want to rush into anything if this TV is about to blow up, leaving us with replacing the kids TV also.

    cheers

    Andy
    ---
    edit: funnily enough we have another TV which is playing up, but its only a few months old and under warranty. Currys sent an engineer out though for some reason, he couldnt fix at site but when chatting to him about the other TV problem, he too backup up what you said about dry joints being the most common cause of CRT failure, and mentioned that its due to RF wearing the solder out over time?

    Anyway, he said to me its a simple fix and just needs the back of the TV removing, the board pulling out and up (?) and looking for any solder which either looks warn away or with a black ring around it, then simply using my own solder gun to restore it back. Removed cover and found lots of dust and the following, any advice as all solder looks intact (I have the below at full 7megapixel resolution if interested:

    http://img.photobucket.com/albums/0603/MADANDY1/Picture320.jpg

    http://img.photobucket.com/albums/0603/MADANDY1/Picture321.jpg
     
  2. JayCee

    JayCee
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    Model no?
     
  3. MAD ANDY

    MAD ANDY
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    not sure exactly, I can find out, but how would that help? are there certain models with this problem?

    I didnt know if it was just a sign of a TV getting old as I've never had a TV 'blow' so dont know what happens exactly.
     
  4. JayCee

    JayCee
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    I'm an engineer, I repair Tv's/Vcr's/Satt/Audio for a living.
    Once I know the model number I can find which chassis is fitted to it and refer to common problems.
     
  5. MAD ANDY

    MAD ANDY
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    looking at homecinemachoice.com reviews, it looks very similar to the JVC AV-32WP2EK and that model number seems to ring a few bells too, but ill have a look round for the manual to see if I can confirm.

    cheers
     
  6. MAD ANDY

    MAD ANDY
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    bttt

    almost ready to buy another tv but dont want to if this is an easy fix, or at least until someone can tell me what it is :(
     
  7. JayCee

    JayCee
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    I already asked you for the model no.........it's on the rear label fixed to the back of the set :confused:
     
  8. MAD ANDY

    MAD ANDY
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    sorry mate, thought you were going to go off the above model number, but confirmed it is the JVC AV-32WP2EK as per the model number on the back of the TV.

    Its turned itself off another 2 times in front of me over the last few days, and degaussed while keeping itself turned on a few times also, other than that its perfect which is the weirdest thing! Wife says its happened to her also though.
     
  9. JayCee

    JayCee
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    It could be something as simple as a dry joint but I suggest you call a local Tv engineer for an estimate.
     
  10. MAD ANDY

    MAD ANDY
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    whats one of them and why/how would that cause the issue I'm having? just so I can try and understand :)

    cheers
     
  11. JayCee

    JayCee
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    All the components are mounted on a printed circuit board and soldered to the board.
    A "Dry Joint" is the term given to a loose solder joint...........so in effect one of the component's connections is intermittently losing the connection.
    Dry joints are probably responsible for more faults in Tv's than faulty components and can be caused by a variety of reasons.........heat, vibration, poor quality solder etc.
    If the problem is a dry joint you call in an engineer who will resolder the suspect joint/joints.
     
  12. MAD ANDY

    MAD ANDY
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    how much for the engineer though? if a few hundred quid I may as well get a new TV thats all I'm thinking.
     
  13. JayCee

    JayCee
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    It would only be "a few hundred quid" if it was something major needed like a new crt and I agree not worth getting repaired.
    But if it's a dry joint you are talking maybe £40-£90.
     
  14. MAD ANDY

    MAD ANDY
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    excellent, cheers for the advice, I'll do a bit of phoning around to see if I can get someone to quote :)
     
  15. MAD ANDY

    MAD ANDY
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    back to the top - new information including pics added to first post
     
  16. MAD ANDY

    MAD ANDY
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    can on one advise at all?

    Would hate to buy a new TV then someone spend a few minutes giving some advice afterwards :(

    cheers
     
  17. ScootermanRoger

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    Hi Mad Andy!
    Replying to your PM to me, if the set is degaussing while it is already on, (you would hear a momentary "bzzzzz", accompanied by a rainbow effect reducing to zero after a second or two) then the problem could be either a dry joint on the thermistor in the degauss circuit (that's the component that when cold allows current to flow through both it, and the degauss coils in series with it, which in turn heats up this component and then rapidly increases its resistance so that it ultimately passes little current.) - or actual failure of the thermistor itself, often just by falling apart! - Or it could be a combination of both. Thermistor cost is quite minor.
    However, you won't find it on the tube-base as shown on your pictures, it is more likely to be on the main board, or possibly on a sub-board, but in any event it will be somewhere near where the wires from the on/off switch join the board. MAKE SURE THE SET IS UNPLUGGED FIRST!!!
    Coming back to that tube-base, if you experience intermittent red or blue or green casts, the solder joints which may be electrical connections as well as anchoring the heat sinks for the gun output drivers look a bit suspect, and could do with resoldering, but in any case, if that bit aint broke, don't try fixing it!
    Good luck!
     
  18. MAD ANDY

    MAD ANDY
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    Hi

    cheers for the reply, no the colour is fine, all the time! Its just the TV will either work perfectly fine for hours on end, or it may only work for a few minutes before it then turns itself off! but when it does this, its not like a controled turn off like when you press the button, more an instant turn off like if switched off at the plug.

    Sometimes it will just switch off and an amber light starts to flash as if trying to warn us (and it must have a timer built in as it wont allow itself to be turned back on for several minutes), other times it will do very fast degaus-type visual refreshes (only 1 at a time though), making a strange clicking sound when it does. Sometimes it may do one and another wont come, other times 3 within a minute! Sometimes it will do 1 to how ever many then suddenly turn off, however when its not doing any of this, the picture is absolutely perfect geometry and colour wise, and sound is not a problem either hence the reason I dont want to bin the TV!

    cheers
     
  19. ScootermanRoger

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    Re the above, I suggest that with the set unplugged from the wall (thus isolating the on/off switch), you inspect the underside of the main board and any sub boards on the printed circuit side for dry joints. These would appear as "grey circles" surrounding the soldered leads, and may well be accompanied by blackening due to arcing across.
    Also, check the mains plug hasn't got loose grub screws on their terminals! Sometimes intermittent faults can be very basic ones!
    Good luck!
     
  20. JayCee

    JayCee
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    MAD ANDY, Sorry to be blunt but I think it's time to call a halt to this thread and call in a professional as you obviously haven't a clue what your'e doing.
    Just phone around a few TV engineers in your area for a quote. :lesson:
     
  21. MAD ANDY

    MAD ANDY
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    ScootermanRoger - thanks very much for your helpful, informative posts :)

    JayCee - er, no thanks! Most of this "thread" is wasted posts of mis-communication and "bttt" etc - so the idea of halting it just because I have asked for help from someone who is now giving me help - no thanks! I appreciate your a TV engineer and so less likely to help because you are doing yourself and others like you out of business, but equally I am not wanting to be ripped off either when I am a competent solderer and just need some advice as to where to look! I do "have a clue what I'm doing" as I am an ex-PC engineer and so soldering, removing circuit boards and stripping down the unit is no problem at all, however as I have no experience with TV's I just need some advice as to where to look for the problem, so thanks but no thanks!
     
  22. red16v

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    Hi, calm down. Jaycee has already suggested to you that you inspect the circuit boards and see if there is a 'dry' joint - he has been most helpful. You've said you are a competent solderer and as such you should have been taught what is a good quality solder joint and what is a poor solder joint. If that is the case then if you feel confident and competent then inspect the pcbs and see if there are any dry joints. It does not matter what the 'kit' is (ie , a tv or a fridge or a pc) to see if the solder joints are ok. Regards, yt.
     
  23. MAD ANDY

    MAD ANDY
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    red - thanks mate, but that came a little from a few PM's I sent to JayCee (when no one was helping at the time) after I took pics of the circuit boards (and couldnt find any dry joints or black marks), but although JayCee read this PM and subsequent PM's (read receipts), no reply was given, which is fair enough if he didnt want to help, after all most of the advice JayCee has posted end with "call a TV engineer", but to ignore the PM's and this thread completely since, then come back on the thread when two other guys such as yourself and ScootermanRoger are helping and then tell me to call it a day and pay someone I think is a little cheeky, thats all :)
     
  24. nig28

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    Hi
    It does confuse things when members send each other PM,s, unless it is personal of coarse.
    These threads, as well as helping the posters also help other members looking for answers and are sometimes quite interesting.
    Nigel
     
  25. Noo

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    I suspect problems in the power supplies. There will be several supply rails within the TV almost certainly supplied by a primary switch mode power supply.

    Essentially these power supplies rectify the mains to approx 350V DC then rapidly switch this DC voltage into secondary storage capacitors (thus reducing the voltage and being extremely efficient).

    Either: -

    1. The main electrolytic storage capacitor is failing, the one that stores the rectified mains (usually 400VDC in the region of a few hundred uFs).

    or

    2. A secondary storage capacitor is failing. They are many voltage "rails" in a TV and each rail will have associated storage capacitors.

    I suspect number 2. I have fixed many freeview/sky boxes where this happens. Some won't come out of standby, some flash an LED.

    The LED flash is usually an indication that a supply rail is trying to "come up" but the "over current" detection circuit is shutting the switch mode controller IC down again. This cycle then repeats giving you a flashing LED and usually a "tick" sound.

    The capacitors fail because of the high switching currents they are subjected to. The energy input via FET from the rectified mains is brutal. So these capacitors get whacked when charging and then are "emptied" by the components attached to that voltage rail.

    The failed capacitors can sometimes show a slightly "domed" top.

    I know this is a bit of a technical post but I hope you all enjoyed it!

    ;)
     
  26. MAD ANDY

    MAD ANDY
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    Completely agree mate! :) The only reason I PM'd JayCee at the time was because much time had passed, hence rather than "bttt" this again, better to PM and point him to the thread, which is the same thing I did to ScootermanRoger and Red ie PM'd them asking them to look here, rather than give me the answer over PM, that way others with the same problem may find the answer and also fix their TV's themselves :)

    excellent post mate, very helpful! :) Interesting re: Sky boxes, as funnily enough ours has started locking up every now and then and wont come out of Standby unless the plug is turned off and left off for a while, although its been fine for a long time, just a short spurt over a few days a few weeks ago! With what you have said that really is a bit too much for me and would require a TV engineer, however with how long it could take, wondering whether to just buy a new TV, but equally I dont want to sling this one because when its working its working perfectly fine! Confused.... DOH!
     
  27. JayCee

    JayCee
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    Unlikely........ going by his reported symptoms he does not have a startup problem which a failed or high ESR capacitor would give.........and these tend to improve as they warm up.
    No, he is complaining of it cutting out which could be any number of things such as a dry joint as has been suggested, a semiconductor failing, EHT failure due to a faulty LOPT.......or CRT flashover which is extremely common............. especially if it is a Philips CRT which has been fitted. All these would give the "Tripping" symptoms he reports.

    The reason I suggested ending the thread is because it started in early May and he is no further forward.....time to call in someone technically proficient who can nail it down.
    MAD ANDY did say and agree in the 14th message in this thread that's what he was going to do, so I was surprised when I came back from my holidays a couple of weeks ago to find a PM waiting for me......I did read it and ticked the "Read Receipt" but I thought I would bow out gently as....honestly........ I don't have the time.....and trying to remotely diagnose a fault which is just dragging on.........there comes a time when you've just got to call in someone who knows the product and can physically examine it/fix it.
     
  28. MAD ANDY

    MAD ANDY
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    This was because I took the back off and took pics and hoped you could diagnose the dry joint from the pics

    yet bizarrely you had the time to reply to the post when others were helping, and reply to this post with more info than any other of your posts on here, bizarre!

    This thread isnt dragging on at all. It would be dragging on if lots of people were advising and I tried all the suggestions and nothing worked, but time here is not the issue, this thread could be 2 years old but if not one single knowledgable person had replied, then its not dragging on, as when someone did, the fault may have been fixed there and then! Now people who are willing to help are posting, I may fix this once I have taken a look!

    and I will once I have actually tried to fix it once myself and failed from suggestions given, cheers :hiya:
     

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