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I have a MIts VS-70803 and just replaced a leaky capacitor on board location C910 200V 820uf. Turned the TV on and a loud buzzing noise coming from somewhere then poof my new capacitor went up in smoke. What could be causing this problem? What are some other parts to check?

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  • Eric Boklep
    Eric Boklep Aug 28, 2010

    This is a rear projection Tv.

  • Eric Boklep
    Eric Boklep Aug 28, 2010

    This capacitor that blew is in front of the convergence chips STK392-040 (if looking in TV from the rear). Before it blew I had picture and sound. And it was hot as heck. From turn on to blow up took about 25 secs. I also noticed a resistor that was out of the board on location R8D22 which i put back in the board. (It was out when I had the buzzing before the capacitor replacement, then I soldered it back in upon new install of capacitor).

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    Ok I'm not sure here but I am testing these resistors and am a little confused. The resistors read Green Blue Gold Gold, which means 5.6 ohm resistor correct? They all read 2.0, 2.1, 2.2. Are these all bad? Thanks

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    So I'm testing these resistors here is what going on. The resistors read Green Blue Gold Gold so it is a 5.6 ohm +/-5% correct? They all read 2.0, 2.1, 2.2 are these bad? And if so are there other parts that could have made these go out? Thanks

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    I tested these resistors and am a little confused. The resistor reads Green Blue Gold Gold which means 5.6 ohm at /- 5% correct? They all read 2.1 or 2.2 are these bad? If so are there any parts that I should test that made those go bad? Thanks

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    I tested these resistors and am a little confused. The resistor reads Green Blue Gold Gold which means 5.6 ohm at /- 5% correct? They all read 2.1 or 2.2 are these bad? If so are there any parts that I should test that made those go bad? Thanks

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    So I'm still a newcomer to this but they are marked on the board IC921 and IC922 are LM2576T-12 QFY831, IC900 is STR F 6626 SK8626, IC401 is LA7845 8U O, IC402 is 9805H 74HC14AP, IC403 is MC74HC74AN JAM9847L. Or these ICDB01

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    Ok the ic's are marked icon the board right? What #'s do you need off of them? The ICBD01 and 2 #'s are STK392-040. Not sure if my replies are getting to you they are not on the solutions area of what we have discussed. Thanks

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    Wow I thinking I'm just overloading my brain. Now for checking these ic's, what do i set my multimeter on? And these ic's are 5 pin LM2576T-12 Do you know what readings I should be getting? Or do you know a good place to find this information? I feel like I'm asking to much from you. Thanks again

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    Sorry caroldon I do not know how to rate the comments. Could you tell me how? And for whats happened so far not sure if you have all the info...Turn on TV the first time and a loud buzzing from somewhere, found a leaky capacitor 820uf 200V a resistor was out of the board and re-soldered some of the STK392-040 pins. Replaced the capacitor and the buzzing was still there after 45 secs or so the capacitor blew same 1 I just put in. I tested all the resistors in the row that had 1 out of board by STK and all on other side by STK they are all bad 16 total. So this is where I am at. Thanks

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    A resistor with Yellow Violet Silver Silver is a .47 ohm /- 10% and they both read .6 are these bad? Thanks

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    What does marking on circuit board D8D83, R8D82,Q8D83 etc double letter ?

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    The STK chips have 21 pins and are really big I thought these were the convergence chips. Or am I wrong? I'm starting to think I'm in way over my head. When I started this the TV does work but only for less than a minute. Should I just order all the IC's and the resistors I found bad 20 the capacitor, also found a couple diodes? On another note diodes should only read 1 way correct? Thanks for your time

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    eagle338, every time I reply to you I click add comment for you. Am I not doing this right? And I do know terminologies although not very well. Am just confused on the wording is all. Remember I am new to this and I do appreciate your help very much. Updates of my journey of fixing this beast found 2 diodes that are bad D-911 just beeps both ways and D-912 reads 453 1 way and then 1809. And I was reading up on buzzing and humming noises, is it possible that the noise is the color wheel or a fan coil or transformer? And another when looking down at the crt fluid should you see the color? Thanks

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    eagle338, on diode test with the red to black to - meter reads 457, with red to - and black to meter reads 1812 board locationD912. D911 just beeps so that is bad correct? Also while testing transistors CB pin should read 1 way, CE pins should read 1 way( how close should the measurements be), and BE pins should not read either way? And as far as the flyback transformer how do I identify that and test it if need be? Thanks again

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    It does not show V mV or anything just a # meter is set on diode check and also has a continuous symbol. I guess I would have to say its in Volt where my rad lead plugs into the multimeter. Sorry I'm really starting to get discouraged but dont want to quit. Thanks again

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    to all would any of the bad parts resistors capacitors diodes transistors cause this buzzing or humming noise? The noise is not coming through the speakers it is in the tv itself.

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    eagle338.....OK so all these parts failing together is causing the buzzing? I guess I just want to know where the buzzing is coming from. What part to be exact. Just getting a bit frustrated. Did you ever happen to come across the service manual? Thanks

  • Eric Boklep
    Eric Boklep Sep 02, 2010

    I just ordered the manual . I know its hard to teach over the computer but I do appreciate everything you have done. My friend got me into this repairing electronics stuff. And now that I try to stay home and do stuff he doesn't give me any straight answers about testing things and what he thinks may be wrong. Thats kinda why I get impatient at times. Hopefully this manual will help me out to. I will keep trying things and be hittin you up more. Thanks again

  • Eric Boklep
    Eric Boklep Sep 08, 2010

    eagle 338, got my service manual yesterday. wish i knew how to read some of that stuff..maybe you could give me some pointers as how to read some of that nonsense? Found another bad capacitor... how do you go about ordering the right diodes? it only gives you the mitsubishi part number and the description stf14. Thanks

  • Eric Boklep
    Eric Boklep Sep 09, 2010

    eagle338 , I figured the diodes out (they are printed wrong in my manual STF14 supposed to be sft14)got lots of parts on the way. As far as pointers mainly what certain parts of the board do. Per DBF , DEFL-MINI, JUNGLE, PWB-RGB of coarse I'm sure if I really looked at it I could figure it out. Thanks for all your help.

  • Eric Boklep
    Eric Boklep Sep 11, 2010

    Hey eagle338, Was wondering if you could do ma a favor if you have the schematics for the VS-70803 Mitsubishi? The 2 capacitors that were bad are at board locations C910 200V 820uf on the PCB-Power board Hot Chassis and C9A08 200v 820uf on the PCB-Main Hot Chassis. Could these 2 capacitors which I believe are in circuit with each other be the cause of the buzzing noise? Or There are 2 IC's locations IC900 STR-F6626 on Power board and IC9A00 STR-F6628 on main board. Question would these cause the caps to blow? I just got the caps to replace them and Ido have the IC's ordered. Just wondering if these are IC's that control the voltage or if I'm in the wrong spot? The part name in the manual of both are IC-H. Thanks in advance. eric

  • Eric Boklep
    Eric Boklep Sep 23, 2010

    eagle338, Hey got an update for you... There is a 70" Mitsubishi TV in my living room that is alive. It's great that with your help I am now watching my TV again. I do still have a small convergence problem with a bowed screen top and bottom. Just need to have the time to get into that. And how do I mark this problem solved and give you thumbs up for your great advice and help? Thanks a million. Eric

  • Eric Boklep
    Eric Boklep Oct 03, 2010

    hey eagle338, my convergence is all haywire. is there a way to get it back to the factory settings.? the first time i tried to do the convergence the red is way off, the blue is ok, but the green lines are horrible (they are wavy on the vertical and in the corners they are bowed in, horizontally they are just bowed in the center). Is there a factory reset to this tv? i cant seem to find it anywhere? everytime i try to fix it it gets worse it seems. Please help. Thanks

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2 Answers

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  • Master
  • 17,129 Answers

For sure you are getting a higher voltage on to the section where the limit is 200 volts. So the Switch mode is irregular and not regulating the power output. Possible failure of the invertor oscillator IC., the power diode. in series.-possible AC factors coming in.
It is easier to trace back logically into the section of the positive voltage that the capacitor receives to identify.
When powering use a variable power supply to check before the full voltage is applied.

Posted on Aug 28, 2010

  • 2 more comments 
  • Donald DCruz
    Donald DCruz Sep 02, 2010

    These are fusible resistors and they are of low value. Please do not attempt unless you are sure or you might end up with more damages. I insist that you must check the circuit in principle before it is switched on disconnect sections and proceed step by step.

    Please rate my comments.

  • Donald DCruz
    Donald DCruz Sep 02, 2010

    You cannot check an IC with the multimeter because of the compostion of the semiconductors within. Only if pins show a short like the voltage rail you can confirm .

    Most of the ICs mentioned are regulators and the pin voltage , the input to output values, current facotrs must be checked and I can go .

    You have still not rated me ....helpful

  • Donald DCruz
    Donald DCruz Sep 02, 2010

    I am off now but will check on your comments soon.

  • Donald DCruz
    Donald DCruz Sep 02, 2010

    The resistors are open but I think your regulators are also faulty..the STK's. Unless they work the voltage is not going to be regulated .Also with the damage there can be fault in the voltage/current path... a cascading efffect... Need to check...Thanks for the review.

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  • Master
  • 4,889 Answers

The buzzing noise usually comes from the deflection circuit. The first thing to check would be resistors to see if any of them are blown.

Posted on Aug 28, 2010

  • 14 more comments 
  • eagle338
    eagle338 Aug 28, 2010

    Did u test the resistor to see if it's ok? Did you also test the other resistors in the circuit? Clearly caps going poof instantly is associated with blown resistors. So I told you that would be the first thing that I would check. I would also check to see if any voltAge regulator ics are fried.

  • Eric Boklep
    Eric Boklep Aug 28, 2010

    Ok, this is my first TV repair on my own and just cant afford to bring it in so please be easy on me. So I will test all those resistors. Also I did find some other bad solders on the convergence chips and touched those up. The board I am working on says power on 1 side, on that side it connects to the board on the right of it with the little wired clips. Is this actually where I should be testing other capacitors? I did trace it across to that board. Keep in mind also that I don't have any schematics or parts #'s to reference. How would I identify the voltage regulator ics? Thanks and sorry I'm such a dummy

  • eagle338
    eagle338 Aug 28, 2010

    Yes the power supply board is the source of the problem. You are working on the right board. Test the resistors and let me know. Make sure you set the multimeter to Ohm meter and set the range to auto(if its an auto-ranging meter). If the resistor is shorted it should read 1. or OL(over load). Once its done please update me on your findings. I will also look for a schematic in my collection. I have the schematics for most Mitsubishi sets.

  • Eric Boklep
    Eric Boklep Aug 30, 2010

    Sorry its taking so long. My multimeter found its final resting place. I'm borrowing a friends tomorrow and hopefully will get this accomplished so I can watch this giant again.

  • eagle338
    eagle338 Aug 30, 2010

    Yeah sure. No problem :)

  • eagle338
    eagle338 Sep 02, 2010

    Right you are. Its 5.6ohm indeed. Yes they have gone bad. Also test the ICs , transistors and diodes in the same circuit. If you dont know what the readings should be just get me the their number and i will see. Ex IC IC80C1

  • eagle338
    eagle338 Sep 02, 2010

    Yes I got your reply. But some of the comments may not be reaching me. Make sure you direct the comments to me.And yes the Ic numbers are correct. Check to see if any of them are shorted. From the numbers you have given me seems like some of them are voltage regulators. So test all of them Vcc of the IC With Respect to ground(You can use the common ground). If an IC is fried you will get a beep on your multimeter and a 1. in your reading.

  • eagle338
    eagle338 Sep 02, 2010

    Please address to whom you are addressing your comments coz I am getting confused. Anyways you should set the multimeter to volt meter. You can get the specs easily by googling for the datasheets of the ics. Ex: if ic no is ic8015 then search for datasheet ic8015. If you can't find any then let me know and I will get you the values. I hope you know terminologies like Vcc, gnd mean?

  • eagle338
    eagle338 Sep 02, 2010

    If memory serves right yours is a CRT projection tv. It does nor have a Colorwheel. And the diode is reading 490Volts? What is the setting? That sounds a bit too excessive. As for the transformer , now that you mention yes transformers can do that but not a very loud noise, the flyback transformer being an exception.

  • eagle338
    eagle338 Sep 02, 2010

    You did not me what unit it is? Volts? mV? Resistance? If you want to know whether its bad then this info is required. And CE CB are present in transistors . C-E means Collector-Emitter junction. CB means Collector-Base junction. As for testing a flyback the link below should be of immense help. However the flyback handles voltages of the range 25,000 to 30,000 volts. SO considering the fact that you are not well versed with electronics I am afraid it can hurt you. As my guru used to say "Your life and limb is worth much more than this". If you still want to go for it then click the link below
    http://www.repairfaq.org/sam/flytest.htm

  • eagle338
    eagle338 Sep 02, 2010

    And I thought we were talking about the samething since you posted this problem!

  • eagle338
    eagle338 Sep 02, 2010

    See one thing I am sure about is that its coming from the HV circuit. There are a lot of things that can go wrong. Sometimes you have to go component by component to identify the source of the problem. Since you have average skills the best bet for you would be to spot the source of the sound and take it from there. I will see if I have a service manual for this unit.

  • eagle338
    eagle338 Sep 03, 2010

    May be it will be easier if we can chat on messenger?

  • eagle338
    eagle338 Sep 08, 2010

    What kind of pointers? Please shoot what type of info you need and I will break it down into simple terms for you. As for the diodes in the last pages you will have whats known as electrical parts list. There the description for each part wil be given. Part number and the relevant technical specs etc.,

  • eagle338
    eagle338 Sep 09, 2010

    Cool. Good luck with the repair. And if you do get stuck somewhere , just whistle :)

  • eagle338
    eagle338 Sep 11, 2010

    Caps cannot cause the buzzing by themselves but they can overlioad the circuit and cause the transformers to do it. And yes the ICs you have mentioned can cause it. The STR ICs are the primary voltage regulators(block over voltage/over load). You can check out the datasheet below if you want to test if the ICs are bad.
    http://www.datasheetcatalog.org/datashee...

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