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My Panasonic PW6 plasma gone pop!


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Old 13-05-2013, 11:45
arbretree
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My beloved Panasonic plasma TH-42PW6 went pop yesterday when I switched it off with the remote. Now there is no red standby light and nothing at on when switched on at socket. Tried another power lead in case fuse gone but still the same, PW6 is probably 8-10 years old but picture is mint in HD, better than the 2 other HD tv's we have so keen to get it fixed. As I'm thinking likely the PSU gone, would any recommend going for a punt on a 2nd hand PSU on eBay for 30 before taking to the repairer as likely 100+ bill from them?
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Old 13-05-2013, 12:00
chrisjr
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What skills do you have with screwdriver and soldering iron? If you have none then I would not take the risk. And of course it may not be the PSU. So the first task is to diagnose the exact cause of the failure then get the necessary parts in to repair it.

The PSU going is the most likely cause but you have to make sure that the PSU did not go pop because of some other fault in the set taking it out. Be a bit of a bummer to swap out the PSU only for the replacement to die in front of you!
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Old 13-05-2013, 13:15
arbretree
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Ok with repairing monitors, had a NEC plasma screen go before and purchased another NEC with a power problem and from the 2 made one good one. Diagnosis is not so easy - not sure how to check the psu. Although I do have access to another PW6 so could I suppose swap the psu from that into the failed PW6 and see if it works - but don't want to blow that psu if something else is causing the failure.
Would it be a prudent approach to try the other PW6's psu?
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Old 13-05-2013, 13:45
chrisjr
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If you do NOT know why the original PSU popped (assuming that it has) then it is not a good idea to go randomly swapping bits round. You could end up with two dead tellies instead of one.

Ideally you would isolate the suspect PSU and test it to see what voltages it is putting out and whether the output is clean, ie pure DC or whether it has loads of crap superimposed on it.

You could then use a bench power supply, that can handle short circuits or excess loads without blowing up, to power the rest of the TV to check if the PSU went by itself or was provoked. And also to see if the PSU popping only affected the PSU itself or if it took something else out as it died.
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Old 13-05-2013, 15:11
arbretree
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I take your point. So step one is to check the output from the suspect PSU, if that is not as it should be then it has failed so then try and ascertain what caused it to fail.
Is it possible also that the PSU may have just failed on it's own?
I remember checking the PSU parts on failed Thomson Sky HD boxes and they showed domed heads on the failed transistors - is this the sort of thing to look for on PSU and other parts?

I'm thinking I can try the basic checks but at some point unless I find clear causes I need to take it in to a specialist repairer.
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Old 13-05-2013, 15:32
chrisjr
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I presume you mean Capacitors not Transistors. Transistors tend to crack open when abused not swell up which electrolytic capacitors can do.

Dodgy capacitors are certainly one cause of a PSU failing on it's own. And is something you can check for. If the top of the case isn't slightly concave then it may indicate a failure. Also look for a sludgy mess round the base which could indicate leaking. Though sometimes an adhesive compound is used to hold the capacitor in place which can confuse matters.

Oh and be wary of exploding capacitors! If you power up a circuit with iffy capacitors or accidentally replace one with the +ve and -ve reversed the cap can turn into a rocket. You don't want to be leaning over it if that happens! And it leaves one hell of a mess behind.

Another common failure is a voltage regulator popping. Sometimes with no visible effects. Or some component has overheated and burnt out. I've seen more than a few PSUs with signs of burning on the PCB and (usually) a fried resistor in the middle of the burnt patch. Trouble is if a resistor burns out you often have no idea what value it was with out a circuit diagram or parts list.
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Old 13-05-2013, 15:39
arbretree
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I presume you mean Capacitors not Transistors. .
Yes - my mistake.

I'll take a look a PSU board and see what I can deduce.
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