Question about Toshiba 55HX70 55" Rear Projection Television

2 Answers

Toshiba 55H70 My unit powers on, then goes to standby. Replaced convergence chips 6 months ago, also re-soldered the area around Z801 high voltage protect ic. Worked great until two days ago. Started to notice image bowing in on the top and bottom, then convergence began to get bad. Image dropped out within 5 minutes after that. Has not powered up correctly since. I have removed the convergence cables as noted by some techs to see if that is a problem again, but it still won't power up. I see nor smell anything burnt on the circuit boards.

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  • gmarkthornto Feb 06, 2010

    I removed the digital converter board and the two convergence ic's. The unit still goes into the slow blink power light mode after about 20 seconds of power-on.

  • gmarkthornto Feb 06, 2010

    I just finished re-soldering the connections to Z801 and the tv powered on and the screen came up. As expected the convergence is all messed up. The image was stable for a few seconds then I heard some clicking noise that coincided with the screen jumping. I shut down the unit, and reflowed solder on the components near Z801 and tried again. The unit came up and remained stable for 30 seconds before I powered it off. How long can it run safely without the convergence chips?

    This is similar to the problem I had after the last time I replaced the convergence chips. I had some sort of problem in the power section that caused the entire image to jump, then the unit would power down. I fixed it by working in the area around the high voltage/x-ray protect chip. I never really saw anything bad but it worked for 6 months. An I missing something obvious?

    Thanks


  • gmarkthornto Feb 07, 2010

    I have reinstalled the convergence chips and the board. The tv is up and running now. The alignment needs to be adjusted again, but the biggest issue is horizontal jiggle. What I mean is the horizontal width is fluctuating slightly. Obviously there are some solder problems I keep coming across. I am using de-soldering braid to remove solder, then re-soldering with lead-free solder.

    What voltages should I measure, and how should I measure them to look for problems? It looks like I have some sort of fluctuation that is causing the horizontal deflection to jiggle. Six months ago I went through with a capacitor checker and couldn't find any bad caps, and there are no visible leaks.


  • gmarkthornto Feb 07, 2010

    You mentioned replacing the caps in the convergence circuit. Which ones would those be? The ones on the main board, the digital converter board or the hyper board?

  • gmarkthornto Feb 08, 2010

    Yesterday before the game I had a very bad revelation. I was in the local Radio Shack getting more de-soldering braid and looked at the solder. While the bins were labeled as containing lead-free solder, that had stocked the standard solder across all bins. I have been re-soldering with standard solder. Needless to say, I am a bit **********. I am going to an electronics supply in San Antonio today to get new solder, then I am going to start working through the board as you suggest. From my latest work, I am back to the situation where the set goes into the standby mode rather than powering up correctly. It definitely looks like a solder problem because I wasn't moving the board between the time I the unit working, but with horizontal stability issues, and now with it not powering up again.

    When you talk about replacing the caps, how far should I go down that road? Do I start with the big ones, or should I make a list from the schematic and order them all up?

  • gmarkthornto Feb 08, 2010

    I replaced with 110's from ACME sales. They appear to be fine. I removed them and the digital convergence board with no change. It appears I have some problems on the power board with solder joints and possibly caps. I re-soldered the area around the high-voltage protect circuit and got the system to power on, but the horizontal hold was jumpy. I continued re-soldering suspect looking connections and now the unit is back in the mode of going directly to standby.

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It could be that this time the convergence module went. I have replaced many convergence ICs and don't believe I have ever had any go out within 6 months. That does not mean that they can't. Remove the leads from the convergence area to isolate the ICs as you said you were told. Now remove the digital convergence board which should be nearby and probably will be in a metal box for noise protection. If you can I would unsolder the convergence ICs to totally take them out of the circuit and just in case one or both shorted out. Once everything I talked about has be removed try the unit. If your problem is in the convergence only your set should work but have an ugly picture. Let me know what you find and we will go from there.

hardrocko

Posted on Feb 06, 2010

Testimonial: "Thank you, I resoldered thoard withe entire power b lead free solder and the image is rock solid. "

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  • Kim Yearick
    Kim Yearick Feb 07, 2010

    The unit can run forever without the convergence circuitry, it will just not be a pretty picture. I am intrigued by your statement about z801 and resoldering. Ever since they removed lead from solder I have seen more bad solder connection problems than ever before. Perhaps you need to go back to the components which you soldered before and clean them thoroughly and use lead free solder to resolder the units. It is possible that some capacitors in the convergence circuit have gone south. They are so cheap I would just replace them all. Try these suggestions and get back to me.



    hardrocko

  • Kim Yearick
    Kim Yearick Feb 07, 2010

    You also mention a problem in the power supply section. I think it's time to measure the voltages and be absolutely sure that they are correct. Let me know.



    hardrocko

  • Kim Yearick
    Kim Yearick Feb 07, 2010

    Just reread your post. Perhaps we are missing something obvious. You mention doing some rework in the power supply. Check or redo that also and use lead free solder. Let me know.



    hardrocko

  • Kim Yearick
    Kim Yearick Feb 08, 2010

    That would be the electrolytic capacitors on all the boards which you mentioned. I believe you are on the right track and need to just keep resoldering until your unit is fine. I've had sets that the very last solder connection, in the worst possible position to get to, was the final problem. Make sure that somehow you don't miss any connections. One other possibility could be a cracked board, crack to small to see, from all the work that has been going on. If that is the problem your only solution would probably be a new board. If you resolder the connections and change out the electrolytics and your unit still does not work correctly you may have to consider a board change. Also make sure you solder any connectors where they go through the board. Another possible problem could be the connectors. Typically they are inserted into the female end and crimped. I remember once having to actually solder the wires to the connector because they were not making connection through the crimp. Let me know how this works out.



    hardrocko

  • Kim Yearick
    Kim Yearick Feb 08, 2010

    I just reread your comments and something struck me. Usually when the horizontal width flucuates it is caused by a problem in the horizontal circuit. I would concentrate on that area.



    hardrocko

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  • Toshiba Master
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Unpluging convergence does not work on all TVs just some of them like Magnavox, also what STKs did you replace old ones with If you went back with 110s that is your problem again use 180s. STK392-110s are the worst ICs they made they fall apart and DO NOT hold up. Did you resolder all of your yoke plugins? Mats Electronics is where I order ics
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Posted on Feb 07, 2010

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