mistergrumpy
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| posted on 22/5/15 at 06:40 PM |
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Electronics and SMD Capacitor
Are there any electronics genuises that can help?
Basically the girlfriend dropped her laptop, quite hard onto the floor and the screen broke. No problem, I got a new screen and no. Just a faint image
which flickers. It appears that the cable that connects the motherboard to the screen has broken two small wires. Replaced that and still nowt. On
removing the motherboard I can see that one way or another a component has melted on the back.
From research it looks like an SMD capacitor. Mid grey ceramic colour with silver each end. From another board I've temporarily bought,
that's faulty and isn't worth the money I paid and is going back, it's 2mm long, 1.25mm wide and around 0.85-0.9mm deep. I've
searched RS Components and Farnell websites and RS shows just 2, 2012 capacitors that are 0.85mm deep. They are around 6.5V and 25v. I don't
know which one to try and if indeed these two are the only ones it could be.
Can anybody advise on anything. I'm pulling my hair out (what's left of it) as a replacement motherboard is proving impossible to find and
I don't have a capacitor measuring function on my multimeter that could help.
ETA that the capacitor seems to be directly beneath the screen plug socket and is totally unmarked. The charger output is 19v and the laptop battery
is marked at 7.2v. Any advice appreciated.
[Edited on 22/5/15 by mistergrumpy]
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theprisioner
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| posted on 22/5/15 at 07:17 PM |
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I have never heard of a capacitor burning out unless it got damaged in the fall, more likely you had a short cct that caused a component near the
capacitor (possibly on the other side of the board) to burn out. Over voltage will cause the capacitor to burn out but that means you still have a
fault. These screens sometimes/frequently require a high voltage psu to backlight them. That is where the contrast is developed the rest is liquid
xtal that only requires a low voltage to stimulate. Does any of my ramblings help?
http://sylvabuild.blogspot.com/
http://austin7special.blogspot.co.uk/
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02GF74
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| posted on 22/5/15 at 07:59 PM |
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From your description it does sound like a capacitor. They usually are marked with the value, dont know if on one or both sides.
Can you take clear photo and post it?
Are you able to find circuit diagram?
Boards can be screen printed with components and value, presumably yours are not.
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peter030371
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| posted on 22/5/15 at 08:52 PM |
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For my sins i own/run an electronics company so this is my bread and butter. If you have a dead smd cap then I am afraid without circuit diagrams its
scrap. Smd caps are never marked and it could be one of thousands of values! As has been already said a faulty cap like this has probably been caused
by something else, even if you did guess lucky something else is probably FUBAR 
Sorry not what you wanted to read
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02GF74
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| posted on 22/5/15 at 09:00 PM |
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^^^^ i would have said that. Re. 1000s of values, the physical size and board voltage would be be less than that, 10s or not more than a couple 100s
a most, still guess work ... and probably not the cause of failure.
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mistergrumpy
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| posted on 22/5/15 at 11:10 PM |
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The damage was caused by the flex cable shorting I think. I guess my only chance of success is somehow to measure the capacitance of the chip on this
other board I have then?I may have to keep the board just for the capacitor and in order to avoid buying a new laptop it seems. 35 quid I had to pay!
Many thanks.
Eta Peter, would it be plausible to send both boards to a company like yours to remove the chip and put it onto the other board and would the cost be
worth it? The laptop was an Xmas present from Xmas just gone. Asus X553M.
[Edited on 22/5/15 by mistergrumpy]
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coozer
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| posted on 23/5/15 at 04:48 AM |
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Try this...
http://www.digikey.co.uk/?WT.srch=1&mkwid=sSGNfk4J5&pcrid=55746693506&pkw=digikey%20uk&pmt=e&pdv=t
Found this on this forum at the top....
1972 V8 Jago
1980 Z750
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mistergrumpy
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| posted on 23/5/15 at 06:26 AM |
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Buying them ain't the problem. It's which one to buy but ta. I'll keep hold for future bits.
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MikeRJ
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| posted on 23/5/15 at 08:53 AM |
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It's virtually unheard of for a ceramic SMD capacitor to melt, though they can crack and go open circuit or occasionally fail short circuit. A
picture of the board might help to determine what it is.
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mistergrumpy
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| posted on 23/5/15 at 11:45 AM |
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Here's pictures of the damaged board and the replacement board also. On the rearside of the damage and directly behind it is the plug for the
flexi cable that connects to the screen and there is 2 cables damaged in it. I think that when I've connected the cable up it has caused a short
through this plug. In hindsight I should have disconnected the battery but it's accessible only by removing the keyboard and I didn't
think it'd matter at the time. How wrong was I! The damaged cap dropped off and I did have it but it's gone now. It was just a small, non
descriptive dark grey mass and just identifiable as the cap by a very small corner visible.
[img]
 
Asus Chip2
[/img]
[img]
 
Asus Chip1
[/img]
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peter030371
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| posted on 23/5/15 at 04:25 PM |
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That looks quite major, to get that much damage I will be surprised if nothing else is not damaged
I am happy to take the good cap of and try and refit it on the other board for you. It won't be pretty but it may work!
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mistergrumpy
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| posted on 23/5/15 at 05:06 PM |
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If you could I'd be very grateful. Pretty I don't mind, we're not all blessed  . Without the cap the laptop still works it's
just that the screen is dark and flickers so fingers crossed. Could you message me an address to send it and I'll cover postage any expenses.
Thanks again.
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02GF74
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| posted on 23/5/15 at 05:56 PM |
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Thats quite a big hole. If board is multi layer, then there May be tracks that have burned out so unless you have circuit diagran, you are unlikely
to fix the links.
This is a laltop right? My suggestion would be to find dead one cheap on ebay and use that to source the parts, no guarantees it will fix it or buy
another laptop. Fairly decent s/h ones can be picked uo on ebay, new ones cane be as low as £ 160(advert on radio so it must be true)
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mistergrumpy
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| posted on 23/5/15 at 06:15 PM |
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Yes I have been looking. The cheaper ones with the same motherboard go for just over £100. Thing is is that this was a present top the girlfriend from
her dad and she feels guilty for being cack handed and dropping it so a repair would be preferential if not the cheapest option. If it comes to it and
the repair can't be done then there'll be no option obviously but I can try I suppose.
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mistergrumpy
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 posted on 31/5/15 at 11:46 AM |
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Just to say thanks a load to peter030371. All fixed and working again. You've gone some way to restoring faith in people (until I go to work in
an hours time!) Thanks again
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peter030371
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| posted on 31/5/15 at 01:56 PM |
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Glad it worked, took less than 5 minutes....as I said before easy when you have the tools 
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