How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Russell H. Your Own Question
Russell H.
Russell H., Service Tech
Category: TV
Satisfied Customers: 10808
Experience:  8+ years of professional experience
Type Your TV Question Here...
Russell H. is online now
A new question is answered every 9 seconds

I have a PN60E550D1FXZA turns on fine with picture and sound

Customer Question

I have a PN60E550D1FXZA turns on fine with picture and sound no problem. The tv stays on for several hours no problem. The issue is if the tv is on for 10 minutes or more, but then accidentally turned off, you won't be able to turn it back on and get both
picture and sound, you would only get sound. The panel will not prime. If you let the set cool down then try again, it turns back on no problem. The tv has issues having picture turn on if the set has already been on for at least 10 minutes. I have noticed
that the VA and VS voltage just doesn't show up what so ever when I try to turn it on after turning it off. There is no way for me to really check components since everything is working properly when you first turn the tv on. I would like to figure out which
board is causing this without shotgunning boards. I understand that this issue could be coming from either the Power supply, Y or X main, possibly the Logic or the main board. I doubt the buffers could be the issue. I have tried bypassing the main board by
doing the PS-on to ground and VS-ON to the 5 volt line, and obviously everything works properly. I made sure to disconnect the buffers and panel from this test. I was honestly hoping to leave it on for a little and see something smoke that would give away
the issue, but nothing. Which makes sense because the tv stays on no problem through several movies, as long as you don't turn it off and try to turn it back on. What kind of test could I do in order to figure out this issue?
Submitted: 2 years ago.
Category: TV
Expert:  Russell H. replied 2 years ago.
Hi, thank you for contacting My name is Russell. I will do my best to provide the right answer to your question. In this sort of problem, it is the fully-heated status of a component that is causing this sort of heat-related problem. Without more information, I cannot tell where that component resides, but: if the component, being fully cool, works A-OK, then use cooling spray to diagnose it. Once the TV has warmed up, all components are warm, more or less. Use cooling spray on just one component after having briefly turned the TV Off after it gets warmed up - and see if that allows it to restart at once. Then go on to the next component, and so forth. (These components would most likely be chips or transistors and/or other solid-state components rather than capacitors or resistors.) If this sounds unlikely, well, the alternative is to inspect all the boards, one by one, for any bulging or leaking capacitors... and replace any that look defective. And try again.
Customer: replied 2 years ago.
Unfortunately, I have already sprayed all of the Main board, and all of the logic board with an upside down can or compressed air. I also sprayed pretty much every transistor screwed into a heat sink without result.
I have looked at all capacitors and all look good. However a capacitor is not the issue otherwise the problem would arise when I first turn on the tv. A transistor that is heating up to much and no longer in spec is more than likely the problem as you suggested earlier, but I already have sprayed all of them on both the power and the sustain boards without a different result, There are surface mount transistors on the back side of every board however, but since the boards are grounded to the tv there is no way for me to spray those.
Also how is it that the transistors will work just fine when you have the tv running for 2 or 3 hours but finally don't work once the tv is turned off and turned back on. That doesn't make sense to me.
Where would a component that only affect start up be located and no longer is active after the set is turned on.
That is the only explanation I can think of. If there is a separate part of a board only used for boot up that could somehow be located near a heat source that caused a transistor to heat up after the tv is on and since it is not in use when the tv is on it doesn't affect the set, but once the tv is turned off and then back on is when we can see the issue appear.
But even in this scenario, I bypassed all but the main board by force turning on the power, sustains, and logic by jumping VSon and Pson to ground and 5v. Shouldn't that transistor either give out or not turn the set on?
Customer: replied 2 years ago.
I guess my next step right now is to get a new can since I ran out with the old one, and try spraying more parts of certain boards. Its a lot of compressed air though.
Are there any suggestions on what board I could start with first????
Expert:  Russell H. replied 2 years ago.
I suggest the power board, esp. if you noticed any voltages missing in the no-video state. The component or board that needs replacing would likely have to do with the initiation of the video when the TV is turned On. That might be any of several places. But ultimately since the spraying did not have any effect.... did you turn the TV Off before spraying, then turn it On again? that might be necessary to test the problem after cooling the component(s) responsible. Again, I recommend getting a service manual for this model - a no-video state will no doubt be listed in its troubleshooting tables and a less scattered diagnosis would be obtained with its aid. Shall I seek a source for such a service manual ?
Customer: replied 2 years ago.
Russell,I did have the tv on when I sprayed the components but you are correct, I should have turned the tv back on to make sure the problem was occurring, then turned it off prior to spraying and then turn it back on to see if the spraying had any affect.
I will get back to you about the results once I get a new can later today.
Expert:  Russell H. replied 2 years ago.
OK. Good luck, and let me know how it goes, at your convenience.