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Toshiba TP55F81 going into protection mode

I recently purchased a the TV in the subject knowing it had an issue. I thought it was the IC convergence chips but found out tonight it wasn't. The problem seems to be within the red circuitry/gun. As the set works fine if the circuit card on the red yoke is pulled off. Leave it on and all you get is a red screen with vertical white concave lines for approximately 10 seconds and then the set goes into protection mode.

Any Ideas???

Thanks

Posted by on

  • bigl31 Feb 01, 2008

    Gents this Set is was made in 1997 so its not new or under any kind of warranty. I just got it cheap on ebay by accident. .99 cents! It worked perfectly fine when I got it home for two or three power on cycles then the problem appeared. The guy I got it from said it had a problem but didnt have it looked at and just wanted rid of it. He had bought a new set already.

  • bigl31 Feb 02, 2008

    Im begining to think this site sucks! What kind of answers are those anyway & why if you know nothing about TV's would you respond. I need someone who has the full service manual who would actually talk to me with some intelligence.



    Thanks for wasting my time & money!!!

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Sir
well if you purachased the tv recently and if any problem is there then you must use your warranty period oderwise if you will do something then it might work against you getting new tv so sir go for the warranty its the best option right now ,i will try and help you if this doesnt work!!

Posted on Feb 01, 2008

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The problem is with the circuit board, there has to be a short somewhere either in the connection to the circuit board or the board itself. The only reason the tv would go into protection is dur to an overheat on the board. My guess is if you replace the red circuit board you fix your problem.

Posted on Feb 01, 2008

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Sir,

Since you have recently purchased that TV... It is best to return it have it changed with a new one... It has still a warranty, right? So why give yourself a problem... It is your right as a customer to get satisfied with what was bought. Remember you pay them for that... Exercise your right!

Go!

Posted on Feb 01, 2008

  • Rommel Balcita Feb 02, 2008

    OKEY FORGET WARRANTY...

    I can offer is to trace the red signal and see where it gets weak. If you put a mostly white screen up you should have more or less equal voltages all the way from the input cable to the cathode pins on the CRT, you have three identical circuits which are relatively simple, so it should be fairly straightforward to trace them as the color signals often go straight to the little neck board and don't even pass through the big main board.


    Check the crt voltages, that should lead you to the problem (although it could be a tube fault).


    First, measure the cathode voltages. One should be a lot higher than the others. If they are all about the same, the CRT is weak. I've seen a lot of bad video output ICs in monitors. Bad soldering on the CRT board is also common with some monitors. The good news is that the entire video circuit is normally on the CRT board, so it's easy to get to and trace.


    The CRT socket is always a prime suspect, even if it looks good, reheat the joints (especially on a intermittent)....


    The loss (or intermittent failure before loss) of a color on a CRT

    monitor is a common and simple problem that can be fixed without any schematic.


    In fact, a schematic cannot help.

    Unplug monitor, remove case, and if you want extra safety, connect a wire to the chassis (ground) first, and then to the HV cap on the CRT.


    Unplug the circuit board from the back of the CRT and unsolder the metal shielding box around it; there are usually tabs that need to be untwisted as well, so that the box can be removed.

    Then use solder wick to remove old solder from the socket leads at the PCB; and then freshly re-solder them (no need to blob as much on as was done originally).


    Replace the shield can, but do not re-twist the tabs (no need, and they could break off) - just re-solder.


    If you used a safety wire, remove it from the CRT cap first, then

    from ground. Then put the case back on, and you will be in business from one to 4 years more.



    If you look carefully, you will note a sponge in the back of the case that (when on) presses against that metal case, thereby creating stress on the solder connections from the PCB to the CRT socket.


    It is that stress which aggravates electromigration of the solder,

    creating the equivalent of a cold solder joint and/or open.

    The reason for the sponge is to help decrease shock on the CRT during transportation.


    There you go... That's all I got, just be careful...

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