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Pincusion on 32" JVC

Discussion in 'Televisions' started by MJ, Nov 23, 2004.

  1. MJ

    MJ
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    Is there anyone out there who has experienced geometry problems with a JVC AV32WX 32" widescreen tv (i.e. pincushioning) I suspect a capacitor. Not having a cct diagram is a bit of a pain. My experience of tv repairs is a little out of date. Most of the tvs I repaired had valves or discrete components back in the 70s and 80s.
     
  2. GalacticaActual

    GalacticaActual
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    have you tried adjusting the pincusion settings in the service menu?
     
  3. MJ

    MJ
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    I haven't because it has been intermittent for some weeks and has only finally gone completely in the last couple of days. So I'm not expecting to be able to bring it in. However it is worth a try. Thanks for the suggestion. I'll try that.
     
  4. GalacticaActual

    GalacticaActual
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    Probably stating the obvious but make sure you wright down all the settings and values first before altering anything. Also get something like digital video essentials that has a cross hatch pattern and other geomatry patterns on it. These will show you just how much everything is out :D
     
  5. red16v

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    Not trying to 'teach Granny to suck eggs' but if I didn't have a circuit diagram I would try the following :

    Look on the pcb for any obvious geometry controls (ie, pots) - the software values may be centred around a 'pot' and that might have a dirty track - might be worth a 'nudge'
    Use an ESR meter to check capacitors around those controls
    change any caps that are near heat sinks

    I'm assuming you're still happy to poke your soldering iron in the back of a tv ? www.mauritron.co.uk might be able to help you with a circuit diagram. Kind regards, yt.
     
  6. MJ

    MJ
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    Excellent idea. Yes I'm happy to poke around. Used to be a TV repair man over twenty years ago. Things have moved on a bit though. Thanks for the suggestion I had forgotten about Mauitron. Haven't used them for about 15 years. Will have a go later. The fault cleared again last night.
     
  7. MJ

    MJ
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    Had a look inside and after giving it a good vacuum inside so I could at least see the boards the fault seems to have gone completely. My bet is still on a capacitor with a dry joint but for now we'll see how it goes. Not much to adjust on the boards. Only pots I could find were on the lopt and the red green and blue. Much as I suspected everything is menu driven. Think I'll leave it like that now. Thanks for the advice anyway.
     
  8. Chris Muriel

    Chris Muriel
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    Modern TV designs tend to ditch old fashioned pots and use lots of DACs or digital pots ("digipots") instead.
    See , e.g., www.analog.com/digitalpots or similar from Xicor and Maxim.

    Chris Muriel, Manchester
     
  9. MJ

    MJ
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    Just for the record in case anyone has the same problem.
    Decided to pull the power card out and take a look as it went completely eventually.
    One of the pins on the transformer (sorry can't be more specific but it's in the middle of the board and is glaringly obvious) was completely open cicuit, it had got too hot darkening the pcb (dry joint) and all the solder had eventually drop away from the joint.

    Back removed, board out and fault found and resoldered and was back working in 30 minutes. :thumbsup:
     

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