TV fixed it self?..please read

[RicB]

i posted about my 2004 NEC PX42VP4A plasma tv, having an issue with turning off as soon as a signal was put to it...well an hour ago i decided to put the PSU back in and test the 15 pin computer hook which i thought i had tested but did not..long story short the computer booted up and thats when i saw kubuntu splash on the screen...and it stayed on : next I plugged in my DVD (RGB component cables) player and it has been playing now for the last 20 mins I am at a loss as to how it fixed itself...i know sometimes that electronics can get..."confused" especially after a power dip/loss and this is my only guess as to what happened and me removing the PSU completely powered down the other 2 boards effectively rebooting them...anyone else ever have this happen? and what was the cause?

thnx

[PlainBill]

Re: TV fixed it self?..please read

i posted about my 2004 NEC PX42VP4A plasma tv, having an issue with turning off as soon as a signal was put to it...well an hour ago i decided to put the PSU back in and test the 15 pin computer hook which i thought i had tested but did not..long story short the computer booted up and thats when i saw kubuntu splash on the screen...and it stayed on : next I plugged in my DVD (RGB component cables) player and it has been playing now for the last 20 mins I am at a loss as to how it fixed itself...i know sometimes that electronics can get..."confused" especially after a power dip/loss and this is my only guess as to what happened and me removing the PSU completely powered down the other 2 boards effectively rebooting them...anyone else ever have this happen? and what was the cause?

thnx

The logical assumption is that one or more of the 437490 solder joints has broken. Your handling has caused them to make contact again. Now you are going to ask "Which one?"

DamnifIknow.

PlainBill

[RicB]

Re: TV fixed it self?..please read

well if it is a solder joint then i know it has tobe on the PSU because that is the only thing i have handled, I think ill go buy a magnifine glass

[RicB]

Re: TV fixed it self?..please read

ok gents riddle me this...how can a tv not work (go to standby when signal is applied or lets stand for more than 2 mins) then have the PSU removed for almost 4 days then have the PSU put back in (with out any repairs) and have the tv work for almost the same amount of days?(tv is back to original problem) ... I cant get my head around this one...i know what bad solder is...i know what a bad cap looks like...I know how a failing cap can act (screen bowing in on the sides when tv starts) I know that some components work fine when there cold but after heating up can start to act up...but this problem is something i have never heard of or seen. the only correlation i can see is the time the PSU was out of the tv and time it was working for (4 days out , 3 days tv working).
has anyone heard of anything like this??


thnx for any help

[tmwalsh]

Re: TV fixed it self?..please read

FWIW, you could have a cracked trace on the PS board. Just recently had a cracked trace on the 'gun' board on a crt. Had to push on the back of the monitor case to get green to display. Found a minor crack...
Surely the board got flexed at least a bit when you removed and reinstalled it, no?

tom

[seanc]

Re: TV fixed it self?..please read

Have you re-soldered all of the connectors and cables that hook up the power supply board?

[weirdlookinguy]

Re: TV fixed it self?..please read

Try resoldering every connector, everything on a heatsink, all coils, and anything that looks like it gets hot on the PSU.

[RicB]

Re: TV fixed it self?..please read

thnx guys for your responses , now there is a new development...the regular composite (yellow rca video) turns the tv off as described when signal hits it...but the RGB component works (which it did not do originally) . There is a weird green hue that shows up during some scenes in a movie...mostly during blue sky scenes, i thought i read some where that bad caps on the PSU can cause this kind of problem.
Do you think the input board is bad as well? or could it have been the problem all along? do i still replace all the caps on the PSU or start looking at the input board?...this is getting confusing


thnx again for any help

[ausheaven]

Re: TV fixed it self?..please read

thnx guys for your responses , now there is a new development...the regular composite (yellow rca video) turns the tv off as described when signal hits it...but the RGB component works (which it did not do originally) . There is a weird green hue that shows up during some scenes in a movie...mostly during blue sky scenes, i thought i read some where that bad caps on the PSU can cause this kind of problem.
Do you think the input board is bad as well? or could it have been the problem all along? do i still replace all the caps on the PSU or start looking at the input board?...this is getting confusing


thnx again for any help

As some has suggested, it is possible that there is bad soldering. One possible problem is heat. Some component is about to fail. As you leave the TV on heat gradually builts up take the soul out of it performance but not enough to break it down. This will be your most difficulty task to find.
Your initialy description point towards this direction.
If you suspect bad caps is the problem try this first. Caps are cheap.

If you are handy with a soldering iron replace the caps (eectrolytic only) one at a time, if after several go you have a fix then run it for a few hours and see if the problem comes back, if it is all OK then you have found the problem. If after replacing every caps and you still have a problem then you have to look elsewhere.
The colour turning green indicate that there is a problem elsewhere.

[RicB]

Re: TV fixed it self?..please read

As some has suggested, it is possible that there is bad soldering. One possible problem is heat. Some component is about to fail. As you leave the TV on heat gradually builts up take the soul out of it performance but not enough to break it down. This will be your most difficulty task to find.
Your initialy description point towards this direction.
If you suspect bad caps is the problem try this first. Caps are cheap.

If you are handy with a soldering iron replace the caps (eectrolytic only) one at a time, if after several go you have a fix then run it for a few hours and see if the problem comes back, if it is all OK then you have found the problem. If after replacing every caps and you still have a problem then you have to look elsewhere.
The colour turning green indicate that there is a problem elsewhere.

thnx for your reply, i did some research and found out that these units run hot I can smell the heat from 5 ft away, when the unit has been on for an hour I hear what i can only describe as a tiny electric motor touching a bit of metal....it is coming from the scan board I know there is no motor back there so I am sure there is something about to die I
will try the caps on the PSU and look for broken trace...but after that i am not sure the tv is worth any more investment of time or money

[Wizard]

Re: TV fixed it self?..please read

Reason I do not like a TV that reanimates themselves is intermittent components or bad solder jonts. I just had caught one (old samsung 42" plasma units) and warned my coworker to pull power supply and check. These SMPS boards are 1 layer type. Not double sided.

Cheers, Wizard