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have bricked 900c? your 900c suddenly won't power on anymore? here's a solution

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afweismann Page Icon Posted 2024-04-23 12:40 AM
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Apologies, I mean that I tested the positive and negative prongs device-side. So imagine an NEC 900 plugged in to wall power and you applying those probes to the corresponding male connector on the back of the 900.

Though, now that you mention that, I took the charged battery from my known good NEC 900C and plugged it into the 900 aaaaaand...

Nothing.
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joval Page Icon Posted 2024-04-27 7:34 PM
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If you don't mind, please humor me by checking the voltage output of the second "charged" battery to assure me that it is above 7.7 volts. Thanks in advance...................................................joval posted from his MP900c + ethernet2wifi adapter + WRP proxy
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andrej2112 Page Icon Posted 2024-04-27 9:14 PM
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¨hi there
Did you find jtag schematics and image?
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andrej2112 Page Icon Posted 2024-04-27 10:27 PM
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find the fuse on the pcb near power connector and check it..
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afweismann Page Icon Posted 2024-04-29 8:18 PM
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7.78 v on the second battery. It holds an ok charge, though definitely showing its age.

No luck on the JTAG schematics or image. The fuse had continuity and I also used a wire to circumvent it. Still nothing.
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joval Page Icon Posted 2024-04-30 9:37 PM
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afweismann - 2024-04-29 12:18 PM


7.78 v on the second battery. It holds an ok charge, though definitely showing its age.

No luck on the JTAG schematics or image. The fuse had continuity and I also used a wire to circumvent it. Still nothing.


IMO that is inadequate... the .08 volts is within component variation if we assume 7.7 +/- %5 is equal to a "dead/discharged" battery.

It appears you have an under-voltage for boot, can you get a battery in the vicinity of 8 volts, or apply 8 volts DC to the MP900 battery prongs? (See my photos above, watch polarity, notched side is positive terminal)?

Charging circuit may be faulty but should still boot off a fully charged battery...which IMO, you obviously lack.

Suggesting just rule out this possibility... the old "close but no cigar" scenario... maybe close but not enough to boot.

best regards and hoping for your success!

Edited by joval 2024-04-30 9:51 PM
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afweismann Page Icon Posted 2024-05-02 12:18 AM
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Oh yeah, that post where you outline exactly that about the battery's voltage. Thank you for bearing with me.

No dice. Sent 8-8.4 volts through on the battery and there was no power draw. Something's not working and I guess I'll figure that out at some point! For now to the parts door for my working 900c.

At least my Mobile Gear II arrived from Japan today and that just needs a scrub, so off to an easier project!

Thank you so much for the help!
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joval Page Icon Posted 2024-05-05 5:31 PM
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afweismann - 2024-05-01 4:18 PM


Oh yeah, that post where you outline exactly that about the battery's voltage. Thank you for bearing with me.

No dice. Sent 8-8.4 volts through on the battery and there was no power draw. Something's not working and I guess I'll figure that out at some point! For now to the parts door for my working 900c.

At least my Mobile Gear II arrived from Japan today and that just needs a scrub, so off to an easier project!

Thank you so much for the help!


Well, hope I wasn't too overbearing or demanding myself... if so, it was my "Evil Twin" commandeering my keyboard and impersonating me once again, (as some on this site will eagerly attest to... haha). Anyway, I learned the cut off voltage for the MP900c. Let us know if you're able to resurrect the little beastie.

Best regards,

Joval
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afweismann Page Icon Posted 2024-05-13 6:31 PM
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No, you were fantastically helpful, thank you!

I just bought some battery acid damaged ARDATA CA-2000Ts off ArchiMark and have moved onto that. The 900C will have to wait a little longer than expected.



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torch Page Icon Posted 2024-05-15 3:09 AM
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afweismann - 2024-05-01 4:18 PM


At least my Mobile Gear II arrived from Japan today and that just needs a scrub, so off to an easier project!

Not trying to hijack the thread but I recently located some programs/updates for MobileGear devices here

https://www.hpcfactor.com/forums/forums/thread-view.asp?tid=21352&posts=2&start=1
May be of use
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afweismann Page Icon Posted 2024-05-16 2:52 PM
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I did see that and it's a fantastic set of resources--thank you for digging those up. I'm wowed that you could even find those.
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