jornada 720 blank screen (but backlight)?

hey folks,

i wonder if my jornada's screen is broken.. it just doesn't work anymore. the backlight turns on and off when switching the power button, apparently the whole device is working properly as well (as i can browse the file system via activesync), but the screen stays dark. well, grey, as the backlight turns on.
as the internal battery was quite low last time i used it, i thought that might be issue and replaced it. now the initial starting-up-for-the-first-time-sound can be heard as well, but still nothing on the screen.

is there a way to repair good ol' jornada? is it a known problem? would be great, as a spend some 150 euros for it and really really like it, comes in handy when listening to lectures in university..


greetings!,
sebastian

mablung[at]gmx[dot]net

the screen cable might have some problem - or might just need adjusting it. (disassembly required)

The Jornada's screen cable eventually develops a break in one of the wires. You can't really fix that type of ribbon cable, and HP doesn't sell replacements. You can try to wiggle the cable until it starts working again, but it'll only work intermittently and for so long before it's completly dead again. About all you can do is find another Jornada that hasn't seem so much use.

There are two ways of patching this, and none of them are good, except if you live in a place like this, where getting your hands on another jornada is just about as easy as acquiring some rocks from Mars or Venus.

1 - try to salvage a very thin wire from some old electronic appliance (like one of those gigantic calculators that were made BEFORE the screen cable was invented). Then identify the broken cable strip and solder a piece of wire from one connector to another. I used to fix laptops this way, but a soldering iron won't do. You need one of those hot air flow devices, used to chance microprocessors and microcircuits. That's hard to find and it costs a heap of money. (unless you have one at work).
And in 1 out of 5 attempts i would just melt the motherboard, or the neighboring contact pins and stuff.

2 - there is some kind of... well.. glue tube...
You know the heating device that cars have in the back window? The thin brownish wires, that keep the window thawed in winter time by heating it a bit.
Well, this glue tube is used to repair such things. It's conductive glue. And i used it to repair screen cable, by coating the wires inside the strip. That, of course, works only with those screen cables that don't have both sides insulated.

Language barriers prevent me from being clear, excuse me. {thumps his head against a nearby wall}

Boy, talk about timing! Right after I read this thread, the following new thread appeared:

http://www.hpcfactor.com/forums/forums/thread-view.asp?tid=6856&pos...

Bet this person can get you the parts you need.

mhm.. okay then. will both try to get that glue and find a working screen.

does anyone know of a downloadable service manual or some explanation how to open up the case and remove the screen? tried to, but somehow didn't get the upper and lower case parts seperated.

thanks for your advice!

That glue isn't going to help you. http://www.jax184.com/pictures/jornadas/jornada5/IMG_0481.JPG
That's what breaks. See how small the wires are? They're also coated in plastic insulation on both sides, so you can't get solder or glue to them without a lot of work. And even if you could, look at the size of them! This assumes that you know where the broken wire even is. It won't be obvious. You'll have to test every pin of the cable with an ohm meter to figure out which wire is broken, and then flex it all along it's length until you see a change in the reading to find the break.

The Jornada's screen is quite hard to get apart. It also usually does more damage to the cable.
But if you insist...

Break the warrenty void stickers in the battery bay, then undo all the T6 torx screws. Also remove the ones at the front edge of the Jornada, and the one in the CF bay. Now you can pop the bottom panel of the Jornada off. Disconnect the screen cable from the motherboard.
Now very carefully undo the snaps along the edges of the "tube" that sits between the screen and the bottom half of the Jornada. The one with the power light in it. You'll probably break the snaps on it, or the points where they go into if you've never done it before. Once it's unsnapped, you can carefully remove the screen half from the bottom half.

Now getting the screen open. Very very carefully remove the HP and model number stickers from the screen. There's a T6 torx screw under both. With both out, you can separate the two halves of the screen case.

From there you can remove the screen cable from the back of the screen and the inverter.

When trying to open a plastic case, always use the electronics hacker's secret weapon, nylon guitar picks. They'll sneak into the tiny gap between parts to unfasten snaps without chewing up the plastic.

mhm.. okay, thanks to your advice i was able to open up the case, braking one of the screen snaps as you anticipated. took me some minutes to find out that you actually need to move the pcmcia-removal-lever 90 degrees to get some latch unlocked.. =)

anyway, the screen cable looks perfekt, not as the one on your picture. will have to find my ohmmeter to test it. might the gpu (or however it's called) be broken?

seems like i've to watch out for some ebay offers. don't know about the spare-part-guy mentioned above, cause shipping and bank fees might easily exceed the price for an entire damaged device here in germany..

i presume all jornadas (from 680 to 728) got the same screen model?


thanks again for your help!

depends on who does it. of course a beginner who never did such tweaking before might break some snaps off, but don't be so negative please






yeah i dunno about the video controller. i'm not so sure that it is always the screen cable that breaks. i bought a dead 720 for 10$, had same blank screen with backlight as yours. after adjusting and cleaning cable, still same... so we (friend of mine helped) took out the cable and tried it in another 720. it worked fine. so it wasn't the cable. if we replaced entire screen it worked so it wasn't something on the motherboard. must be something inside the screen but never tried to fully troubleshoot the thing to find out the cause... would be an interesting experiment.

I have 3 bad Jornada cables. None of them LOOK broken, even under a magnifying glass. I honestly don't know which wire or where is broken. Yet all three are bad.

The screens in the 680, 690, 710, 720 and 728 are slightly different models, but all compatible with each other. A screen cable from one will work in any other.

I've yet to see a Jornada with a bad video controller. It's almost certainly the cable, or the screen.

"or the screen" = what do you mean by this?

I mean that if you have a screen that's not working, it's possible that it's the screen that's not working .

ok but what parts of it could be at fault?

The screen controller board, the small board on the back of the LCD which takes the incoming video signals and then sends it off to the panel drivers. I doubt that it's managed to fail, but it's possible. The cable is still much more likely.

Thanx for making that comment, cmonex. I'm a techno-idiot, and I just successfully transplanted the screen cable from my 680 to my first 728, and brought that 728 back to life!