Repairing a lot of MobilePro 900s

Hi All,

I recently got a lot of 20 MobilePros 900s from eBay and was disappointed to learn that none of them worked. I was able to swap a non-working screen and get one of them working and updated with Cmonex's 4.3 ROM. To test, I removed the battery and backup battery, waited for a few minutes and plugged each in. They group into the following in terms of symptom:

8 Charge light turns on, unit does not turn on. No startup chime, no noise.
5 Charge light does not turn on, unit does not turn on.
2 Unit turns on but screen is dark (startup chime happens and you can hear button clicks, etc.). Tried sapping working screens but no screen. Brightness buttons have no effect.
1 unit has vertical lines on screen. Ground connection was broken so tried swapping a working screen with good ground and vertical lines still present.
1 unit the keyboard works but some of the keys type 2 different keys
2 units turn on but ROM appears to be corrupted. One unit just hangs after stylus calibration while the other the screen won't refresh.

Varying amounts of physical damage; one cracked screen, trashed keyboards, broken plastic, etc.

Most seemed to have working main batteries and one came with a stylus so not a complete loss with the working unit. I'm betting that I have about 10 working screens.

These units appear to have come from a lot of non-working units from a police department auction. The police department appears to have hooked these up to an external monitor and used for alcohol breath testing devices; there is alcohol testing software baked into the ROM that is persisting after hard resets and the updated ROM.

Any ideas to try to resurrect some of these? I thought it would be a fun project to get some of these working but am not having much luck.

I have two other complete working 900s that have been upgraded so am somewhat familiar with these but am hoping you all might have some ideas.

Thanks!

The 900 series has a 64MB PSA on it, so is the alcohol app in that rather than ROM?

You'll need the service manual, PCB wiring diagrams, tester tools, flux, solder and a soldering iron to start resurrecting these by the sound of it.

I was afraid that might be the reailty - I'll begin disassembly of the non-working bases to see what shape the mainboards are in... any particular components I that are suspect?

I managed to get one more compete unit working but it isn't recognizing my newer CF cards so haven't been able to update the ROM. I tried to push files via IR but only one of my 4 working units seems to have the drivers.

I did more thorough testing on the batteries and only 1 is good but I am hoping I can re-cell some of the rest assuming the charging/protection circuits are OK.

For the one bad keyboard you could try swapping out with those others, but, lastly you can use ASCII code workaround by pressing <alt + code> together like <alt 64>( I have a keyboard that lacks working " and - keys and the ascii code works for most part). Those keyboards are so wonderful to type on...

Quite a menagerie of sick critters...some may have burned out fluorescent tubes. I had a Jornada 720 with horizontal lines that had a defective ribbon cable which I diagnosed with a voltmeter with continuity check...I soldered a thin wire to the circuit boards and ran it thru the hinge...took care of the problem. Good luck exploring...you will learn much.

C:Amie...sounds like you've been in the trenches in the past...good advice.

Edited by joval 2019-06-23 3:35 AM

CE4 comes with IR drivers in the OS, so it isn't a driver issue. It's probably the transport app. Just use Total Commander https://www.hpcfactor.com/scl/932/Christian_Ghisler/Total_Commander/version_2.5

CF Cards: 32GB FAT32, no exFAT and no NTFS.

Most of your issues are likely bad contacts/traces. Patchable, but you need to know where that are going and what to expect on each line. If you can get one fully working then you can at least continuity test as a comparison between the working one and the dead one... but without knowing where the traces are going, it'll be a chore and a half.

You will have to send them to Louis Rossman
https://www.youtube.com/user/rossmanngroup

Thank you for the advice... I'll try downloading Total Commander to see if that works and will make sure the CFs are formatted correctly. It was odd since they work in some but not other MPs... but I need to load these up with useful software in any case.

I found a listing for 9 refurbished mainboards so ordered them; hopefully they work. Rossmann may be getting bored due to running out of repairable mac mainboards lol

Sounds like you are having trace problems and eve cap issues in that. There is a good chance that the lamp isn't powering. Use your cell phone camera or webcam to see if it blinks.

Thank you - I'll do that with the bad screens to see if they have the image but no back light.

I am going to take a good working board and then test all of screens that are not physically damaged, keyboards, etc.
I was testing via the DC jack; I need to go through and test all of the non-working units via a charged battery in case the DC jack is the issue on any of them. Turns out that just about all of the batteries were bad after more thorough testing but I hope to be able to re-cell with good 18650s
Inspect the boards to see if there are any obviously blown caps, burn marks, etc.

I'll get into these more next weekend and post some pics.

Test the IR lamps with the phone I meant, screens you just need a bright torch for

Ah! Will do!

OK just an update and conclusion to this story. I purchased the lot of 20 MP 900s from an eBay auction. I tested the screens with a good unit and they all work, so it's definitely down to the mainboards. I then found another eBay lot of 9 "refurbished" boards but they all turned out to be toast - the anti static bags they came in had loose surface mount components rattling around. I decided that both lots are going back - the price paid for both lots could get me a few demonstrably working MP 900s in excellent condition if I wait long enough. I thought about keeping the screens and keyboards for the 20 lot but can't imagine with the slow pace of MP900s showing up on the market that there would be enough reasonably priced bad screen but working MPs floating around to warrant keeping the working parts. My skills at tracing down faults and re-working on PCBs is probably not sufficient to warrant further work on these. The lot of 20 was an e-waste broken parts lot from a Police station that was using these for alcohol testing on patrol vehicles.

So just down to my two original working MP 900s...

Agree...not worth going down that rabbit hole (better used by a really heavy drinker who needs a lot of backups)...

Shame, CmoneX had some ideas about how you might resurrect some of them. It did sound like it was going to be a full blown hassle though!

The only silver lining is that the seller of the 9 defunct mainboards refunded me and didn't want to deal with the expense of shipping the boards back. Anyone want them? Happy to send these to someone who can try to fix them rather than taking them to local e-waste bin. 2-3 had a loose surface mount component or two, but for most of the rest the charge light lit up, just no display on a working screen. In a few cases the startup sequence would happen for a few seconds and then it would turn itself off.


Edited by voneschenbach 2019-06-28 2:11 PM

That sounds like a capacitor problem.