Replaced LCD; still no backlight

Discussion in 'Other Device Manufacturers' started by Half-Wit, Feb 18, 2009.

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  1. Half-Wit

    Half-Wit Newbie

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    Does anyone have any 'hardcore' tech data? I have an X51v with no backlight. Hard reset; no help. Replaced the LCD and touch screen from a non-working X51v with unknown problems; no help. Bought a new LCD on eBay; still no help.

    I am starting to suspect that the backlight is not getting power but I would rather have some wiring data BEFORE I start poking around with a multimeter. I found lots of places to buy repair parts or repair service but not a repair manual or repair data.

    Also, how do you separate the touch screen/digitizer from the LCD without breaking anything? They seem sort of glued together but I see that they are sold individually.
     
  2. Konrad Pierce

    Konrad Pierce Village Idiot 2.0

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    Before answering your question, HW, and without any insult intended, it's helpful to know

    - are you confident in your Axim disassembly/reassembly skills; is it possible that you've actually damaged something inadvertently, perhaps even through something as rare (but drastic) as ESD?
    - do you know how to use a DMM?
    - are you willing to do any soldering (if necessary) to effect a repair?
    - are you reasonably certain that - between your various screens - you definitely have at least one which should work perfectly?
    - are you certain you've purchased the correct part? (Do you have any part numbers?)

    You can be comforted by the fact that "poking around" with a multimeter cannot damage the screen, nor the Axim, battery, or any other circuitry. Provided you restrict your probing to the LCM itself, you can hardly even force the device to require a soft-reset, though of course you may see all sorts of interesting things happen to the screen. (All assuming that you do not inject any power from an external source while measuring. The LCM as an entire entity uses less than +5VDC and sucks less than 200mA at full blast.)

    You'll find that even though they don't make 'em anymore, the X51v is still considered a desirable PDA model - it's arguably one of the best ever made, and may even be the very best after a little upgrading. As a consequence, people are always willing to purchase X50v/X51v units in any condition, either to refurb for resale or use as part salvage for the same. The usual crowd of substandard part makers and vendors saturated this niche long ago, so much that it's impossible to assure real quality until you've got the piece in your hands and see it (not) working.
     
  3. Half-Wit

    Half-Wit Newbie

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    Thank you for responding.

    The first Axim I bought on eBay works except for the backlight. I bought another on eBay that would not turn on (inspection revealed that liquid contaminated the board and caused some corrosion around one chip). I expected to use the LCD in it to solve the problem in the first one. When that backlight also didn't work I bought a 'new' Axim X51v LCD from one of those Hong Kong eBay dealers with the same result. Now I am guessing that either all 3 LCD's are bad or (call me crazy) m-a-y-b-e there's a problem on the board.

    I was a military Electronics Tech 40 years ago and have worked with computer equipment in the private sector for 30+ years. DMM's, soldering and ESD safety are second nature to me. I am reasonably confident that, having disassembled 2 units at least 4 times each as I tested and retested parts combinations, I have not damaged anything and all parts, especially ribbon cables (worse than working on laptops!), are properly reconnected since symptoms are unchanged.

    I am well aware of the qualities of this product which is why I have chosen it as my first PPC. It will replace my well-worn Palm Pilot IIIc, also an excellent product in its class. I have repaired many of them over the years, too. I know just enough to know when to ask for help before I do irreparable harm.

    I do hope you can shed some light (pun intended) on this problem.
     
  4. Konrad Pierce

    Konrad Pierce Village Idiot 2.0

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    Aha, you're obviously no bumbling amateur (like me ;) ) - I apologize if I accused you of such.

    If you're confident that you've attempted to operate the unit with at least one working screen yet it still didn't work then of course some other component has failed. I would suspect hardware failure on the mainboard.

    It's possible you've got a corrupted ROM and your device is "bricked". Since this is just firmware it's (almost always) a trivial matter to fix: you might be able to just install the latest WM ROM update, you might be forced to resort to various bootloader tricks and tools.

    I would suspect the actual LCD ribbon connector. Like all connectors, it is subject to all sorts of mechanical failures ... it's possible that simply using an electrical contact cleaner will remove enough oxidation/corrosion to restore normal function.

    The same applies to the power source - in this case the removable Li-ion battery. Confirm that battery itself is in fact providing normal power (3.7V at full charge) and that the contacts are indeed doing their job.

    What's left after answering these obvious questions? Nasty troubleshooting; Something Important on the mainboard has failed. Maybe a trivial little resistor or cap on the charging circuitry, maybe the PXA270 processor or 2700G chip is zorched, maybe it's just a case of bad RAM. If you enjoy the challenge of this prospect then go for it, otherwise simply replacing the entire mainboard module (or the entire PDA) is your best bet.

    Very detailed specifications and tech-talk can be found all over the place if you comb through Aximsite, xda-developers, ppcgeeks, and handhelds.org. Good luck ;)
     
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