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Thread: Panasonic TH-P50V20A intermittent audio problem

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    Default Panasonic TH-P50V20A intermittent audio problem

    Hi guys, My trusty plasma has developed an unusual fault. Every so often the audio goes scratchy and distorted, drops in volume a little and then returns to normal. It does this on any input including FTA TV. Any ideas? Thanks



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    Try connecting an external speakers to your TV and if the external speakers sounds fine then the problems is with your TV speakers.

    Maybe a Firmware update might help if possible on your plasma.

    Or, this link might help


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    I should have said, its hooked up to a 5.1 amp. The TV has been on for 3 hours now and the problem has not occurred during that time. It only lasts for a couple of seconds when it happens, might not happen again until tomorrow. Its very erratic, it only occurs when you really need to hear something!

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    Well if it continues, I would go through the elimination process - remove the amp and all it's connections and just test the TV's audio speakers and go from there.. Comprende Amigo

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    Quote Originally Posted by Johnno View Post
    Well if it continues, I would go through the elimination process - remove the amp and all it's connections and just test the TV's audio speakers and go from there.. Comprende Amigo
    Yeah done all that. Its the TV I'm afraid, and its not a mechanical noise, the picture even changes slightly . Thanks for your suggestions

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    Quote Originally Posted by sdrambo View Post
    Yeah done all that. Its the TV I'm afraid, and its not a mechanical noise, the picture even changes slightly . Thanks for your suggestions
    That might suggest power supply board or mainboard decoder/demux being weird... if it's really sporadic, it'd be worth at least checking the mainboard for dust/other accumulation...mainboard looks like a rabbithole repair =)




    Power board looks pretty straight forward tho'




    Parts for these sets are now hard to get/NLA, and you have to hunt for them or end up with good, used..ie;

    You'd need weigh the possible repair cost, against the notion of replacing with a newer device ~ this unit would be nearly 10years old? That's pretty much service done, time for retirement age with this gear =)
    Last edited by wotnot; 06-08-20 at 07:58 PM.

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    Would definitely be looking at power supply caps.

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    Quote Originally Posted by Reschs View Post
    Would definitely be looking at power supply caps.
    Yes I will. The set still has a beautiful naturally coloured picture, but reluctantly it may have to go :-(

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    Quote Originally Posted by Reschs View Post
    Would definitely be looking at power supply caps.
    Any in particular I should replace?

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    Quote Originally Posted by sdrambo View Post
    Any in particular I should replace?
    That's sort of like asking which haystack has the 10mm long needle, and not the 15mm long needle hidden in it =)

    Intermittent sound is one thing ~ intermittent sound with associated/coincidental change in display, hints at a common problem, and both of these are symptoms of that.

    I should've asked before ~ in what way exactly does the picture change when the sound problem manifests itself?

    It's a hard call - panasonic make their own caps, and they're usually pretty good....there'll be a low voltage supply block on the powerboard, could be 5 or 12 volts, might create both rails...I'd start poking there. Just looking at the mainboard image, I can see a couple of mosfet bucks, good chance they're doing the 3.3volt rail....it's always at times like this, one wishes they had schematics

    Typically I just grab the multimeter, and as a first check measure all the voltage rails, and hope I find one hovering at the low end of spec...and start there. For intermittent faults, I'd just attach probe channels to the likely suspects of interest, and graph the voltages on a 5minute rolling window, turn the set on and hope/wait for the fault...if I'm suspecting a power rail.

    Else daft logic here ~ plasma sets run pretty hot ; hotair gun on wide dispersal and see if the fault can be coaxed by heat.

    One would also consider, after a decade, exactly what shape whatever heat transfer material was used under that heatsink is in.

    You might open it up, and immediately spot a bulging cap, or find it covered in enough dust you can start planting your own garden : ducks in a row, examination & investigation first, then solution =)

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    Quote Originally Posted by sdrambo View Post
    Any in particular I should replace?
    Any that look like they are damaged, leaking, bulging etc.

    Otherwise, simply replace all of them.

    There are plenty of threads that are similar to this one.

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    As already said.. If you can not see the culprit, replace all the electrolytic on the PSU

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    Quote Originally Posted by wotnot View Post
    That's sort of like asking which haystack has the 10mm long needle, and not the 15mm long needle hidden in it =)

    Intermittent sound is one thing ~ intermittent sound with associated/coincidental change in display, hints at a common problem, and both of these are symptoms of that.

    I should've asked before ~ in what way exactly does the picture change when the sound problem manifests itself?

    It's a hard call - panasonic make their own caps, and they're usually pretty good....there'll be a low voltage supply block on the powerboard, could be 5 or 12 volts, might create both rails...I'd start poking there. Just looking at the mainboard image, I can see a couple of mosfet bucks, good chance they're doing the 3.3volt rail....it's always at times like this, one wishes they had schematics

    Typically I just grab the multimeter, and as a first check measure all the voltage rails, and hope I find one hovering at the low end of spec...and start there. For intermittent faults, I'd just attach probe channels to the likely suspects of interest, and graph the voltages on a 5minute rolling window, turn the set on and hope/wait for the fault...if I'm suspecting a power rail.

    Else daft logic here ~ plasma sets run pretty hot ; hotair gun on wide dispersal and see if the fault can be coaxed by heat.

    One would also consider, after a decade, exactly what shape whatever heat transfer material was used under that heatsink is in.

    You might open it up, and immediately spot a bulging cap, or find it covered in enough dust you can start planting your own garden : ducks in a row, examination & investigation first, then solution =)
    Often there is a common culprit, so its a case of replace C x,y,z according to much smarter people than me who care to post this sort of help.

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    Quote Originally Posted by wotnot View Post
    That's sort of like asking which haystack has the 10mm long needle, and not the 15mm long needle hidden in it =)

    Intermittent sound is one thing ~ intermittent sound with associated/coincidental change in display, hints at a common problem, and both of these are symptoms of that.

    I should've asked before ~ in what way exactly does the picture change when the sound problem manifests itself?

    It's a hard call - panasonic make their own caps, and they're usually pretty good....there'll be a low voltage supply block on the powerboard, could be 5 or 12 volts, might create both rails...I'd start poking there. Just looking at the mainboard image, I can see a couple of mosfet bucks, good chance they're doing the 3.3volt rail....it's always at times like this, one wishes they had schematics

    Typically I just grab the multimeter, and as a first check measure all the voltage rails, and hope I find one hovering at the low end of spec...and start there. For intermittent faults, I'd just attach probe channels to the likely suspects of interest, and graph the voltages on a 5minute rolling window, turn the set on and hope/wait for the fault...if I'm suspecting a power rail.

    Else daft logic here ~ plasma sets run pretty hot ; hotair gun on wide dispersal and see if the fault can be coaxed by heat.

    One would also consider, after a decade, exactly what shape whatever heat transfer material was used under that heatsink is in.

    You might open it up, and immediately spot a bulging cap, or find it covered in enough dust you can start planting your own garden : ducks in a row, examination & investigation first, then solution =)
    I am not brave enough to check voltages with the back off and the set running. In the last 6 months I have had the back off and removed accumulated dust and cleared the vents and heatsinks etc. I did not spot any bulging caps during that inspection as I am aware of this problem since my old Humax days. I am currently getting the audio from the optical out to see if this works. It takes a lot of time because the fault does not have a time frame

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    Quote Originally Posted by sdrambo View Post
    I am not brave enough to check voltages with the back off and the set running. In the last 6 months I have had the back off and removed accumulated dust and cleared the vents and heatsinks etc. I did not spot any bulging caps during that inspection as I am aware of this problem since my old Humax days. I am currently getting the audio from the optical out to see if this works. It takes a lot of time because the fault does not have a time frame
    Ok, thanks for drawing your situation better...you still didn't answer question about how the display is changing?

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    Quote Originally Posted by wotnot View Post
    Ok, thanks for drawing your situation better...you still didn't answer question about how the display is changing?
    The display sort of shimmies along with the distortion. I took the back off today. The caps all look fine. I will post photos later today. The set was manufactured in June 2010, it has served us well. Due for retirement, I just dont know what to replace it with now the Panasonic OLEDs are no more. I have not had a good run with LG appliances.

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    Hmmm.... common input component would be the signal mux.... this IC top left;



    If the powersupply measured sane, I'd likely annoy that chip with the hotair gun (or conversely coldspray when fault develops)

    All a waste of words I guess, considering you're thinking of buying anew ; sold 'as is' with intermittent fault, it's probably still worth something

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    Hi Attached are the images of the PSU and main board.. Whoops no images. Dont know what went wrong there
    Last edited by sdrambo; 08-08-20 at 03:21 PM.

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    Quote Originally Posted by sdrambo View Post
    Hi Attached are the images of the PSU and main board.. Whoops no images. Dont know what went wrong there






    For those of you following this, the actual album link is better, as you can get a zoomed view -->

    Look at the mainboard ~ now that I see it, as mentioned before but even more so now, I would have that heatsink off to clean behind it & renew thermal transfer material ; my gut feeling is there's a dust storm behind there.

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    Thanks wotnot, so I remove the big black heatsink and renew the thermal paste. That I can do, does noy seem to be too many traps there! For some reason I am blocked for attachments posting. I will have to email admin

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