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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Dry joint on 28" Hitachi wide screen TV?
Hi All,
A mate has given me his 5yr old 28" Hitachi wide screen TV and it comes with an intermittent fault where it just cuts out. Apparently if it does this you can *sometimes* switch it back on with the remote and sometimes not. He said if it fails to come back on, lifting one corner and dropping it (gently?) often sorts it out? I had a quick word with the guy in the local electrical shop today and he suggested this was not an unknown fault on that and smaller models in the range and of that age. So, before I start tapping about all over the place looking for dry joints, any TV gurus out there have any idea if there is a 'common' area that I could start with please? If I do get it all sorted I will probably give it to my elderly Mum / Dad. All the best .. T i m |
#2
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Failure to come on suggests PSU as a likely candidate, though not the
only one. But you need to be aware of the various dangers in TVs before poking about. Theres caps that store mains V, live lines on boards, 25kV EHT, with storage in the tube, and one or 2 HT lines as well for eg focus (maybe a few kV) etc. Plenty of ways to cook. NT |
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#4
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T i m wrote: Hi All, A mate has given me his 5yr old 28" Hitachi wide screen TV and it comes with an intermittent fault where it just cuts out. Apparently if it does this you can *sometimes* switch it back on with the remote and sometimes not. He said if it fails to come back on, lifting one corner and dropping it (gently?) often sorts it out? I had a quick word with the guy in the local electrical shop today and he suggested this was not an unknown fault on that and smaller models in the range and of that age. So, before I start tapping about all over the place looking for dry joints, any TV gurus out there have any idea if there is a 'common' area that I could start with please? If I do get it all sorted I will probably give it to my elderly Mum / Dad. All the best .. T i m Look around the flyback transformer. I was told (by the man who repaired one of my TVs with this kind of fault) that the amount of copper in that area makes a very efficient heatsink and makes reliable soldering difficult. MBQ |
#6
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Hi All,
A mate has given me his 5yr old 28" Hitachi wide screen TV and it comes with an intermittent fault where it just cuts out. Apparently if it does this you can *sometimes* switch it back on with the remote and sometimes not. He said if it fails to come back on, lifting one corner and dropping it (gently?) often sorts it out? I had a quick word with the guy in the local electrical shop today and he suggested this was not an unknown fault on that and smaller models in the range and of that age. So, before I start tapping about all over the place looking for dry joints, any TV gurus out there have any idea if there is a 'common' area that I could start with please? If I do get it all sorted I will probably give it to my elderly Mum / Dad. All the best .. T i m Out 28" hitachi did exactly the same - it was rented so an engineer (!?) came out and knew exactly where to look, he just remade a couple of joints (I couldnt tell you where on the board though) and it has been find since - he said it was a common fault. |
#7
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On Thu, 20 Jan 2005 13:44:16 -0000, "a" wrote:
So, before I start tapping about all over the place looking for dry joints, any TV gurus out there have any idea if there is a 'common' area that I could start with please? Out 28" hitachi did exactly the same - it was rented so an engineer (!?) came out and knew exactly where to look, he just remade a couple of joints (I couldnt tell you where on the board though) and it has been find since - he said it was a common fault. Hmm, I re-soldered all the main joints today and now I have a *dead* telly ;-( The problem is I may have 'firmed up' the intermittent fault? I have spoken to an ex TV repair mate and he might pop in to point me in the right direction, or get one of his TV repair mates to sort it for me. ;-( All the best .. T i m |
#8
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oh do crosspost this lot to sci.electronics.repair.
NT |
#9
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I thought it might be around that area but other things (like
overvoltage to the HT) can cause TV's to shutdown can't it? HT overvoltage would be a PSU fault. If you mean EHT overvoltage... On second thoughts it might not be set up like that, I dont do tv repairs any more. SMPSUs can be a right pain now with their overzealous protection schemes, so youre right its not necessarily a psu fault. Just a question of starting where things are most likely. Thats the way when you cant divide and conquer, and with todays overprotected psus you often cant. Its good you know the risks, i just never know whos going to read these posts on a public ng. NT |
#10
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On another note, regular readers here may remember me rambling on
about a sony TV suffering from green screen/flyback lines/PSU shutdown. I used to bash it hard, it was getting worse. Cassandras prophesised that it would finally fail as the tube was going. In fact, for some unexplained reasn, it has performed flawlessly for the last 6 months. Perhaps a tube short burnt out or fell off? Burning shorts out is a standard repair after all, and the associated psu shutdown suggests possible high fault current. Who knows I once experimentally ran a Sony tube fairly heavily overvoltage (heater +70%, drive V increased, and 10% EHT boost), and it did this fairly regularly. The tube would arc over and so on. It was the only tube I saw that turned PAL into Never The Same Colour Twice Dont think I'd do that sort of thing now though NT |
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