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Found a working mirror of handhelds.org ftp repository

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munchausen Page Icon Posted 2021-01-09 10:30 PM
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I've looked for a mirror of handhelds.org a number of times without success, and tonight I was looking for something else and just stumbled upon it. I thought others might find it useful too. It's here
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ArchiMark Page Icon Posted 2021-01-09 10:42 PM
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That is great.

Thanks for sharing!

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joval Page Icon Posted 2021-01-10 4:05 AM
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@Munchausen: Now that's a lucky find...I browsed through it , easiest to start in root directory and work down the tree to jornada. The memory info chips etc very useful, and LCD power inverter (jeez...340 volts with fluorescent tube lit up but a whopping...1,200 volts on start up ...no wonder that thing has a bite to it...having been zapped a few times repairing bad ribbon connector a time or two.

Great to know that info is tucked away in a safe place. Did you see that readme about an ON/Off switch zimage and modules (fails 10 percent of time to awaken)... interesting as it actuallly used the power on button.

Sort of an exotic web site...Max Planck Society types and all. If I join they'd make me "walk the planck" for sure (well...once they got to know the real me)!

@ArchiMark: Hey, good to hear you're back on the trail. DId you ever get your MP900 upgraded to the CMonex ROM? Oh, I got the Aironet wifi card working on my J720/Devuan/SSH/X11/RasPi hybrid...so NO ethernet tether...furthermore...seems as fast as the tethered ethernet card to me. So may not really need the Ambicom 54Mbs card if 11Mbs will do (but do keep trying and thanks for your help doing all that).




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munchausen Page Icon Posted 2021-01-10 10:53 AM
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I cloned the whole thing for posterity. It comes to 12gb but I think there are a few large files under .git/svn and so on that can be deleted

Edited by munchausen 2021-01-10 10:53 AM
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joval Page Icon Posted 2021-01-11 3:16 PM
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munchausen - 2021-01-10 2:53 AM

I cloned the whole thing for posterity. It comes to 12gb but I think there are a few large files under .git/svn and so on that can be deleted


Great! You may want to add your motherboard photos to it for completeness.

You say you can repair motherboards...wow. I have a display but the touch/digitizer doesn't work...LCD is fine. I fussed with the ribbon cable but still not working...I checked cable for continuity, it's ok, and swapped motherboard and problem persists. Any tips or suggestions on how to troubleshoot...
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munchausen Page Icon Posted 2021-01-11 5:18 PM
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I'm having a go. I've got a J720 board that suffered from being fed too high a voltage I think. A few components were obviously burned to look at, but after removing them it seemed that the output of a burned MOSFET was still shorted. By looking at datasheets I found that it was the output driver of a buck converter, and removed the capacitor and diode from that drive circuit too, and the short has gone, so one or other of those was fried, but both looked OK visually. I'm hoping that I've now found all the dead parts, but I wont know if anything else has also been fried until I replace them, and if any of the larger chips are dead it's game over. The hardest part has been identifying parts, because these little discrete components have obscure codes written on them that have little relation to the actual part numbers. If I do get it going again I'll make a post about it.

Touch screens and LCDs on these devices are custom and a real pain because of that, and probably not repairable I'm afraid. Sometimes FPCs get tiny cracks in them, or it may be that the digitizer has taken a knock. If you have some patience you can figure out the connections for it and check if it registers a touch using a multimeter. The interface for a resistive touch screen logically looks like two resistors, so you're looking for four wires, and have to figure out which pair is the X resistance and which pair is Y (you can sometimes tell from looking at the touch panel itself). Then you can put a meter across each pair and look for resistance changes when you press the screen. But even if that does help you diagnose the fault your chances of repairing it are still very low I'm afraid.

Edited by munchausen 2021-01-11 5:19 PM
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joval Page Icon Posted 2021-01-12 6:35 PM
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munchausen - 2021-01-11 9:18 AM


Touch screens and LCDs on these devices are custom and a real pain because of that, and probably not repairable I'm afraid. Sometimes FPCs get tiny cracks in them, or it may be that the digitizer has taken a knock. If you have some patience you can figure out the connections for it and check if it registers a touch using a multimeter. The interface for a resistive touch screen logically looks like two resistors, so you're looking for four wires, and have to figure out which pair is the X resistance and which pair is Y (you can sometimes tell from looking at the touch panel itself). Then you can put a meter across each pair and look for resistance changes when you press the screen. But even if that does help you diagnose the fault your chances of repairing it are still very low I'm afraid.


Thanks for both the excellent explanation and the clues on where to start. I remember disconnecting a tiny branch of ribbon cable I think from the touchsceen...looked like 4 wires/leads. I trimmed off 1mm or so, which as worked on other J720's in the past, but not this one. I'll check the resistance and see if can get a response. I'm impressed with your abilities tacking the Motherboard...but although they appear so mysterious, I guess it's electronics like anything else...and I suppose quite robust at that. Good luck. Thanks again. :0


Joval
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munchausen Page Icon Posted 2021-01-13 8:40 AM
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Yeah repairing electronics is not that much different from repairing any machine, it's just harder to see how it all works because a lot of it is hidden from view, and that part ends up taking most of the time. Also you may need quite a lot of expensive equipment to do some repairs (solder rework station, oscilloscope, meter, logic analyser etc).
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