Question about Toshiba 50H71 50" Rear Projection Television

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Toshiba 50H71 TV, blown fuse 852, replaced STK392-110

Hi I have a Toshiba 50H71 TV, had a blown fuse 852, and replaced convergence ICs STK392-110 with STK392-110 T. Now TV will power on for a second or two you can her HV then will not power on again unless you unplug from outlet. I have soldering and TV fixing experience, also check soldering spots and jumpers 010, 050 as many suggested on this post.

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  • miran35 May 28, 2010

    Hi



    it is not arcing problem.



    power supply turn off after one of it's conditions is not met

  • miran35 May 29, 2010

    Hi



    I have service manual, yes it is Over load problem or one of the modules do not work properly, so is there a way to find out which module is causing shutting down



    Miran

  • miran35 May 29, 2010

    Hi



    There is not enough time to measure voltage because TV turns off in 1 sec

  • miran35 May 29, 2010

    Hey



    Please read may first post, "I have soldering and TV fixing experience" there so I have millimeter, oscilloscope(I hope you know what it is), My question is again how do I find which module is shutting down power supply, Can I remove one of the fuses ex F889 for audio amp Vcc or F470 120V and TV will still power on?





    Miran

  • miran35 May 29, 2010

    OK let's live jokes aside and get serious, You replayed 8 times and there wasn't any real answer ping pointing yet.
    Please do not user abbreviations like DMM or w.r.t because I do not know what they mean (English is my second language) Yes I did check stand by regulator Q840 for 5v. and red stand by LED is blinking at the front.

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  • 4,889 Answers

What do you mean by can hear HV? Does it sound like some kind of high pitched buzzing noise? Did you check for arcing near the flyback?

Posted on May 28, 2010

  • 5 more comments 
  • miran35 May 28, 2010

    Hi



    What do you mean by can hear HV?



    I mean HV starts for a sec or two then turn off looks like on or more conditions are not meet.

    Is there a way to see which condition is missing?




    Miran

  • eagle338
    eagle338 May 28, 2010

    Did you check for arcing near the flyback like I said in my previous post?

  • eagle338
    eagle338 May 29, 2010

    Ok.. DO you hear any clicking noise before it turns off. Over load on one or more circuits cause the relays to kick in and turn off the set to prevent damage. I have a service manual for this model so let me know when you are here and we will finish this today.

  • eagle338
    eagle338 May 29, 2010

    Since you have the service manual, yo should start by checking the specified test points marked in the manual especially near the voltage regulators. Try it and let me know.

  • eagle338
    eagle338 May 29, 2010

    That is why we are using a digital multimeter. Most digital multimeters have a voltage of their own. If your multimeter has that feature touch the probes on the anode and cathode of the voltage regulator and set the digital multimeter in ohm meter mode. Measure the resistance across it. Also check the voltage across it then report back along with the IC number and the voltage recorded. The only question is do you have such a meter?

  • eagle338
    eagle338 May 29, 2010

    I know what an oscilloscope is. Its for getting the wave forms. Now if you have an oscilloscope you should also know that there is something known as residual voltages. Your primary targets are the 3 pin voltage regulator ICs. Measure voltage w.r.t ground. I know the set is off but your DMM should do the trick. Trust me on this. I wave worked on 10's of Toshiba sets and I have helped people fix their sets. Thats how I got the Toshiba badge that you are seeing. For any reason if you cannot follow my instructions, please let me know and I will break it down for you and I will tell w.r.t to the service manual that you have.

  • eagle338
    eagle338 May 30, 2010

    That my friend is because you have ignored my advice. Sorry about the abbrevations though. As for the schematic looks like you don't have a comprehensive schematic. I see 3 lines 9V, 5V and 3.3V if the regulators are normal then you would have all 3 at proper ranges. Did you test them and see if any of them are overloaded? P.S if your service manual does not have a detailed schematic please let me know and I will give it to you. I am only trying to help you.

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