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Old April 14th, 2013, 02:26 PM
pop1020 pop1020 is offline
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Problem with an LG monitor

I have LG Flatron w2252TQ screen which stopped working....black screen, no power light. After changing the cables made no difference I decided to open it up and test the power and logic boards. After close inspection of the power board I figured at least three radial capacitors (contained in two groups of five) were defective. I noted the value 470μF 35volt and ordered these from a local supplier.
A couple of days later (when they arrived) I de-soldered them all and tested them. There were in fact four blown. I re-soldered all ten back in place only changing those that were defective. I reassembled the screen and tested it....it worked...end of story...well it should be.

However when tidying up I noticed that not all the capacitors had the same value as I had assumed. Of the four, two were 470μF35v but two were 1000μf 16v....I had replaced them all with 470μF 35v!
The increase in voltage won't make much difference but what about the reduction in the microfarad value?? The tolerance is 20% at a Max temp of 105C

Any observations or comments most appreciated.

Lionel
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  #2  
Old April 15th, 2013, 02:38 PM
Digerati Digerati is offline
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You are right, the voltage will not matter because that is the capacity. The capacitance may matter but without knowing the type or purpose of the circuit they go in, it is impossible to tell what affect they may have. In any case, I don't see this being a safety issue (as far as excessive current or heat issues), but I can see this causing problems with display stability or quality and if me, I would replace those caps with the right value caps as soon as possible.

Note capacitance in series adds. So if you cannot find 1000F caps, you can add another 470F in series (if physical space permits) to get you to 940F, and within specs.
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Old April 16th, 2013, 08:38 AM
pop1020 pop1020 is offline
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Hi there,
Thanks for the reply. I had thought of adding another in series as you suggested but this would involve adding in a new pathway to the board which as you probably know is a real pain. I will probably replace them as you suggested but I will now have to find the original circuit diagram to find the exact location of each capacitor.
The hardest part of all this is re-opening the case!!!!
Lionel
PS the epoxy putty worked really great!! I will add a couple of photos to my other post to give a sort of closure to it. L.
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Old April 16th, 2013, 01:29 PM
Digerati Digerati is offline
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Quote:
PS the epoxy putty worked really great!!
Ah! I am bad at paying attention to usernames and did not realize this was the epoxy putty/broken case system. I am glad that worked - and hope it lasts.
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Old April 16th, 2013, 06:28 PM
pop1020 pop1020 is offline
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“did not realize this was the epoxy putty/broken case system”

Well actually it's not...the “putty/broken case” is the Asus portable belonging to my wife, that my daughter dropped. This post concerns the broken screen from my daughters system.
The common factors are my daughter.... who breaks things.... and myself who is obliged to repair them.
I have considered locking my daughter in the garage until she is eighteen....which , logically, will cut down my workload.
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Old April 17th, 2013, 03:58 PM
Digerati Digerati is offline
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The common factors are my daughter.... who breaks things.... and myself who is obliged to repair them.
Well, been there, done that - on second go-around now with the grandkids.
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