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pengyou Page Icon Posted 2011-02-09 8:11 AM
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H/PC Philosopher

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The displays on both of my J720's are not nearly as bright as they used to be. I go through phases of using them and then not using them. Also, the batteries are really weak. Is that the reason for the faint display? The cases and screens still look almost brand new. If I can resolve this problem I may try to dig one out again and use it as a dedicated function machine - maybe ebook reader or movie player.
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CE Geek Page Icon Posted 2011-02-09 8:32 AM
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The J72x displays do seem to dim somewhat over time, though the battery may well be contributing to the problem. Needless to say, I'd try a better battery first. There are still some on eBay these days.
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t6nna Page Icon Posted 2011-02-11 1:12 PM
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Factor Fanatic

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If you have adapter connected, then you should get full power it needs. No need to buy new battery just to test your screen.
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wallythacker Page Icon Posted 2011-02-11 1:38 PM
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H/PC Elder

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well peng, none of my 3 have dimmed. so why others and not mine? as suggested, use AC to eliminate the battery as a cause.
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Rich Hawley Page Icon Posted 2011-02-11 3:08 PM
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Dimming of the screen over time is normal. Normally it is the CCFL, but sometimes it may be the invertor board supplying the CCFL its power. I've actually pulled apart a few Mobilepro screens and replaced the CCFLs in them with those from broken LCDs before, just to get the nice bright and crisp screens you see with new screens. I've also swapped out invertor boards, but that rarely has effected any significant change. Either you have enough voltage to stimulate the lamp, or you don't.
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pengyou Page Icon Posted 2011-02-14 4:28 PM
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H/PC Philosopher

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Thanks! I will give it a try. I am skeptical about buying a battery for this. I bought two for my nec 880 that were supposedly "brand new" but they only held a charge for about an hour - they probably were brand new, never used before, but the chemical activity and potential in the battery is diminished. I will search this forum to see about rebuilding the batteries.
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C:Amie Page Icon Posted 2011-02-14 4:29 PM
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Don't you have AC to test the brightness against?
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arlex Page Icon Posted 2011-02-14 7:13 PM
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Factorite (Elite)

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Hi everybody!
For those interested to replace the CCFL tube with LEDs, here is a most interesting 3 pages article on how to hack a Jornada 680 - "LEDs replacing CCFL backlight" at http://spritesmods.com/?art=ledbl
The author says that there is no doubt about the gain in the brightness and colour shade of the screen.
I guess that the forward converter can be made more simple with a non-programable IC.

Edited by arlex 2011-02-14 8:07 PM
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chiark Page Icon Posted 2011-02-14 8:37 PM
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H/PC Sensei

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It's definitely the CCFL lamp in the backlight, unfortunately...
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