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Prime does not turn on after charging
08-11-2019, 08:01 AM
Post: #1
Prime does not turn on after charging
Hello all,

yesterday evening i switched on my rarely used Prime and it told me immediately that batteries are low and i should charge. Thats what i did overnight (The screen switched off and no Led was on, is that normal?). Now the Prime seems to be dead. What i have tried:
  • SYMB + ON
  • SYMB + ESC + ON
  • SYMB + RESET Pin
  • SYMB + ESC + RESET Pin
  • C+F+O + ON
  • C+F+O + RESET Pin

Alle of these i tried with battery only, with battery+usb, with usb only.

Are there any ideas, how i can bring the device back to life?

Thanks,
olr
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08-11-2019, 11:59 AM (This post was last modified: 08-11-2019 12:00 PM by Tim Wessman.)
Post: #2
RE: Prime does not turn on after charging
Remove your battery, plug in the calculator, while plugged and running (is it running?), insert battery again. Does it remain on? Leave it plugged in for a few minutes. Try unplugging. Does it stay on even for a second? If so charge and keep using and you are good.

If not, find a replacement battery.

TW

Although I work for the HP calculator group, the views and opinions I post here are my own.
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08-11-2019, 12:39 PM
Post: #3
RE: Prime does not turn on after charging
Hello Tim,

(08-11-2019 11:59 AM)Tim Wessman Wrote:  Remove your battery, plug in the calculator, while plugged and running (is it running?)

No it's (also) not running with battery removed and plugged. Screen stays off, no led turns on. I tried with the original power supply and some others. I measure a current of 100mA. (During charging i measured a current from 670mA which is down to 300mA now).

Thanks,
olr.
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08-11-2019, 02:02 PM
Post: #4
Try a different cable
Clean the port and try a different micro USB cable to be sure.
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08-11-2019, 02:10 PM
Post: #5
RE: Prime does not turn on after charging
Hello,

(08-11-2019 02:02 PM)striegel Wrote:  Clean the port and try a different micro USB cable to be sure.

I cleaned the port and tried different chargers, different usb ports on different PCs/Laptops with four different cables (all combinations). Still dead.

Thanks,
olr.
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08-11-2019, 08:40 PM
Post: #6
RE: Prime does not turn on after charging
I have a vague memory of someone (probably Tim) mentioning checking for a loose display connector.

— Ian Abbott
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08-12-2019, 03:34 PM
Post: #7
RE: Prime does not turn on after charging
Thanks ijabbott

(08-11-2019 08:40 PM)ijabbott Wrote:  I have a vague memory of someone (probably Tim) mentioning checking for a loose display connector.

I removed the backcover and checked every connector. They all look (and feel) good. However i did not remove the upper PCB. If that is necessary, i would need more detailed instructions as just removing all visible screws does not make it fall apart.

olr.
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08-12-2019, 04:58 PM
Post: #8
RE: Prime does not turn on after charging
(08-12-2019 03:34 PM)olr Wrote:  However i did not remove the upper PCB. If that is necessary, i would need more detailed instructions as just removing all visible screws does not make it fall apart.

I advise you NOT to attempt removing the motherboard. It is glued pretty strongly to the back of the screen and there's nothing interesting back there for troubleshooting.

Assuming this is a G1, there should be a UART_TX pad on the motherboard. I haven't done this in a long time, but you can try connecting to it (3.3v TTL, 115200 bauds, 8 bits, no parity) and see if there's a boot log transmitted upon reset.
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08-13-2019, 11:11 AM
Post: #9
RE: Prime does not turn on after charging
(08-12-2019 04:58 PM)Jean-Baptiste Boric Wrote:  
(08-12-2019 03:34 PM)olr Wrote:  However i did not remove the upper PCB. If that is necessary, i would need more detailed instructions as just removing all visible screws does not make it fall apart.

I advise you NOT to attempt removing the motherboard. It is glued pretty strongly to the back of the screen and there's nothing interesting back there for troubleshooting.

Assuming this is a G1, there should be a UART_TX pad on the motherboard. I haven't done this in a long time, but you can try connecting to it (3.3v TTL, 115200 bauds, 8 bits, no parity) and see if there's a boot log transmitted upon reset.

Have they removed the UART pad from the G2?

Tom L

Tom L
I think therefore I am-Descartes
I think therefore you are-Gorgias
You're not here to think-Army Sergeant
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08-13-2019, 01:31 PM
Post: #10
RE: Prime does not turn on after charging
I think there was an older firmware that would turn on with the screen completely dimmed. The calculator appeared off but was actually just dimmed to zero. Long shot but did you try to increase the screen brightness? Hold down the ON button and press the '+' key.
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08-13-2019, 03:56 PM
Post: #11
RE: Prime does not turn on after charging
(08-12-2019 04:58 PM)Jean-Baptiste Boric Wrote:  I advise you NOT to attempt removing the motherboard. It is glued pretty strongly to the back of the screen and there's nothing interesting back there for troubleshooting.

Assuming this is a G1, there should be a UART_TX pad on the motherboard. I haven't done this in a long time, but you can try connecting to it (3.3v TTL, 115200 bauds, 8 bits, no parity) and see if there's a boot log transmitted upon reset.

Ok, I will not touch the motherboard. It's a revision A (NW280AA). I'm not experienced with attaching to UART TX. Any hints, where i can find it on the board? I would need to find the hardware and time (and motivation) to start this experiment.

(08-13-2019 01:31 PM)ndzied1 Wrote:  I think there was an older firmware that would turn on with the screen completely dimmed. The calculator appeared off but was actually just dimmed to zero. Long shot but did you try to increase the screen brightness? Hold down the ON button and press the '+' key.

Just tried that, unforunately this didn't work either. I didn't use the Prime very often but when i heard about a new firmware i upgraded.

Thank you,
olr.
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08-14-2019, 08:22 AM
Post: #12
RE: Prime does not turn on after charging
Did you try to use the HP Prime Connection Kit to see if it recognises the physical Prime when connected to the PC using a usb data cable (not the ones used for charging only)?

Jose Mesquita
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08-14-2019, 01:22 PM
Post: #13
RE: Prime does not turn on after charging
(08-13-2019 03:56 PM)olr Wrote:  It's a revision A (NW280AA). I'm not experienced with attaching to UART TX. Any hints, where i can find it on the board? I would need to find the hardware and time (and motivation) to start this experiment.

On a revision A, the UART_RX and UART_TX pads (labeled as such) should be located near the bottom-right of the SoC chip, the one with red goo corners. To interface with it you need a 3.3v TTL UART, which is commonly done with a USB TTL serial cable, costs about €10. Plug the USB serial cable in, open a terminal emulator to it, connect the ground wire to the USB plug shield, the RX wire to the UART_TX pad (no need to solder for a quick check) and reset the calculator. A bootlog should appear on the terminal emulator.

If you're not sure about your setup, short the RX and TX wires of the USB serial cable together and type stuff on your keyboard. The characters should echo back on the terminal emulator.

(08-13-2019 11:11 AM)toml_12953 Wrote:  Have they removed the UART pad from the G2?

It's still there, but it's located on the back of the motherboard now, along with a bazillion pads including JTAG. The official firmware doesn't output anything at all over the UART, but I assume the U-Boot/Linux port done by Zephray Wenting can use it (haven't tried it yet).
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08-15-2019, 04:02 PM
Post: #14
RE: Prime does not turn on after charging
Hello all

(08-14-2019 08:22 AM)jebem Wrote:  Did you try to use the HP Prime Connection Kit to see if it recognises the physical Prime when connected to the PC using a usb data cable (not the ones used for charging only)?

I just tried, but the Connection Kit does not show the Prime. (I did not expect it does as the OS did not recognize the Prime, no ding-dong)

(08-14-2019 01:22 PM)Jean-Baptiste Boric Wrote:  On a revision A, the UART_RX and UART_TX pads (labeled as such) should be located near the bottom-right of the SoC chip, the one with red goo corners. To interface with it you need a 3.3v TTL UART, which is commonly done with a USB TTL serial cable, costs about €10. Plug the USB serial cable in, open a terminal emulator to it, connect the ground wire to the USB plug shield, the RX wire to the UART_TX pad (no need to solder for a quick check) and reset the calculator. A bootlog should appear on the terminal emulator.

Thank you, i found it. I used the USB TTL cable, that i used to flash my WP34s. I think i did it right (echoing worked) but nothing was displayed in the terminal when resetting the Prime :-(

olr
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08-15-2019, 05:55 PM
Post: #15
RE: Prime does not turn on after charging
(08-15-2019 04:02 PM)olr Wrote:  Thank you, i found it. I used the USB TTL cable, that i used to flash my WP34s. I think i did it right (echoing worked) but nothing was displayed in the terminal when resetting the Prime :-(

Assuming there's no manipulation error (like putting the TX wire on UART_TX), that's really bad news. Either there's something electrically wrong with the motherboard that prevents it from booting or the first NAND sector got somehow corrupted.

You can check if the motherboard is alive by probing the NAND chip with an oscilloscope to see if the SoC is talking to it. If it is (and the NAND chip isn't dead), your HP Prime can theoretically be fixed either with a JTAG interface to load and run the recovery in RAM or with a NAND flash programmer to rewrite the boot sector+recovery on the NAND.

I'd say the JTAG option is the only one with a reasonable chance of success, if you're not afraid to get your hands really dirty. Just in case, you probably want to contact HP and ask them if they're willing to take a look at it and repair it out of warranty (I assume you'd prefer maximizing your chances of having a working calculator at the end).
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08-25-2019, 02:13 PM
Post: #16
RE: Prime does not turn on after charging
Hello everybody,

sorry for the late update. I decided to give up on that Prime. I tried (most of) the hints again with no success. Contacting HP was not easy. I finally ended with one supporter, who claimed an HP Prime from 2014 cannot exist.

Anyhow the Prime was never my favourite. Better the Prime is dead than my HP50g knock, knock, knock (my point of view, no pun intended).

Thank you all for the support.

best Regards,
olr.

P.S.: If anyone is interested, I offer the Prime (only the Prime with cover) for free (I'd like to get a postcard in return but its not mandatory).
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