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Blue band from top to bottom of screen

While I was watching the set, the screen suddenly went dark, then this blue band appeared. It's a 47 inch set, the band is about three inches wide. I bought the set used about a year ago for $300. I pulled the boards out to look for obvious things, found no loose connections or burned parts. It appears (from the solder side) that diodes D452, D455, and D456 have been replaced at some earlier time. The diodes are mounted near IC7001, one of the convergence amps, on the heat sink side. I see that the convergence chips are a pretty common fix for these TVs, but I'm not seeing this symptom being mentioned too often. I've got tools, a digital Fluke, and skills, but no O-scope. Please help, watching Lost on the small screen really sucks.

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  • CyberGregg Feb 27, 2008

    I should have posted the make and model in the request.
    Panasonic PT-47WX54J
    sorry...

  • CyberGregg Mar 07, 2008

    I replaced the convergence chips today, checked the values of all the nearby precision resistors all were in tolerance. I did continuity checks on all the nearby diodes, they all still appear to be one-way devices.
    Powered it up, and got the exact same screen as before. What to do now?

  • CyberGregg Mar 07, 2008

    I have no intellegible image on the screen, so set-up menus are not an option here. http://www.fixya.com/uploads/images/4049...
    Perhaps this is horizontal deflection problem? What parts drive that circuit?

  • CyberGregg Mar 10, 2008

    I've already swapped the convergence amps.
    I'm hoping that MikeMaierTV's information will lead me to the proper fix.

  • CyberGregg Mar 12, 2008

    Thanks MikeMaierTv,
    I have checked the resistors in the area of the yoke connectors (and pretty much every other one on the whole board) and have not found any bad ones. I don't think my skills are enough to do in circuit testing on transistors with just a multimeter. Most of the electrolytic caps are anchored to the board with blobs of silicone glue-like stuff, I've pulled a couple off the board to test for short or open conditions (no lucky guesses for me there...)but I fear damaging the board if I try to test them all that way. I eagerly await your help...

  • CyberGregg Mar 16, 2008

    Any suggestions besides replacing the convergence ic's (already done that...)?

  • CyberGregg Mar 16, 2008

    Any suggestions besides replacing the convergence ic's (already done that...)?

  • CyberGregg Mar 24, 2008

    I'm giving up and calling the Authorized Panasonic Repair Center in my area. This was a real waste of ten bucks. I would be less disappointed if I hadn't continued to get the "replace the convergence IC's" solutions after I had already posted that I had already done that. If you don't have the ability to read why would anyone trust your technical ability? Once I get the set fixed I will post that the repair has been done, and anyone who wants to know the real scoop on this fix can talk to me....

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It is certainly possible that the problem is the flyback transformer.
This does appear to be a deflection problem.
Only trouble is, I tried fixing a projection tv with a fluke meter like yours and it is too difficult to isolate the problem.
I suggest investing in maybe a used one from ebay or similar place.
You can end up replacing just about every component without one.

Posted on Mar 16, 2008

  • Hjalmer Lamminen
    Hjalmer Lamminen Mar 25, 2008

    http://www.manualuniverse.com/manager/pr...

    Here is a link to your model service manual.

    Hope this helps.

    Have you tried pulling the center wire from the flyback transformer yet?

    If the tv stays on with that unplugged it may be a problem with the flyback.

    You may have a problem with a resistor, capacitor etc. in the high voltage section just after the flyback.

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Well this aint no convergance problem, I have seen this once or twice, first find where the yokes plug into the main deflection board ( three conectors with four wires each ) Now there should be some damaged resistor right in this area. Also in this area will be a large transistor it may be shorted, this all started becuse a capacitor in the high voltage let go. I will get the service manual out and get more specific when I get back to work but see if you can find these resistors locate around the Yoke plugs and see if there shot

Posted on Mar 07, 2008

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This defect is not very common but is usually found around the horizontal drive and amplifiers circuity.
I would suggest to check nearby the flyback transformer for a defective low value resistor, diodes and possibly dry capacitor(s)
If you can get the schematic diagram it will definitely help.
Good Luck.

Posted on Mar 07, 2008

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Hi have a nice day! Go to menu. Select either video or setup. Select convergence. There could be one or two setups. Try the automatic setup first. If it's just a minor problem this should work. Let it do it's thing and if all goes ok you should have a good picture. If this does not solve the problem do any other convergence setups available. If this does not solve the problem you probably have a bad digital convergence box.

Posted on Mar 07, 2008

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Malfunction of the convergence ics

Posted on Mar 01, 2008

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