[SOLVED] HELP, I replaced my phone's USB board and now the modem no longer works

Hardware Librem 5
1

So I replaced by phone’s USB board following instructions here: USB-C board replacement - Purism user documentation

The procedure involves disconnecting six antenna cables (two on each card and two on the USB-C board itself), removing those two cards (the modem, and the wifi card), then putting them back.

I used toothpicks to remove the cables as carefully as possible. When putting them back I made sure they seemed well attached (by slightly attempting to pull them out and verifying they don’t move).

So, good news is that the USB board works (charging is fast again, external screens work). Bad news is that it no longer connects to the mobile network. It was working yesterday before I started the disassembly, so I’m pretty sure I must have done something wrong.

The phone receives signal, sees available networks, but just won’t connect. I can’t make phone calls, can’t connect to mobile Internet.

How can I troubleshoot that? I ran the command below, does it contain any useful information? ([…] replace things that look like unique identifiers to me)

purism@pureos ~ % mmcli -m /org/freedesktop/ModemManager1/Modem/0
  -----------------------------------
  General  |                    path: /org/freedesktop/ModemManager1/Modem/0
           |               device id: […]1c
  -----------------------------------
  Hardware |            manufacturer: QUALCOMM INCORPORATED
           |                   model: 0
           |       firmware revision: MPSS.JO.2.0.2.c1.1-00032-9607_GENNS_PACK-1.351938.1  1  [Nov 26 2020 02:00:00]
           |          carrier config: ROW_Generic_3GPP
           | carrier config revision: 05010822
           |            h/w revision: 10000
           |               supported: gsm-umts, lte
           |                 current: gsm-umts, lte
           |            equipment id: […]81
  -----------------------------------
  System   |                  device: /sys/devices/platform/soc@0/38200000.usb/xhci-hcd.4.auto/usb1/1-1/1-1.2
           |                 drivers: option, qmi_wwan
           |                  plugin: broadmobi
           |            primary port: cdc-wdm0
           |                   ports: cdc-wdm0 (qmi), ttyUSB0 (qcdm), ttyUSB1 (at), ttyUSB2 (at), 
           |                          ttyUSB3 (at), wwan0 (net)
  -----------------------------------
  Status   |                    lock: sim-pin2
           |          unlock retries: sim-pin (3), sim-puk (10), sim-pin2 (3), sim-puk2 (10)
           |                   state: enabled
           |             power state: on
           |             access tech: lte
           |          signal quality: 76% (recent)
  -----------------------------------
  Modes    |               supported: allowed: 2g; preferred: none
           |                          allowed: 3g; preferred: none
           |                          allowed: 4g; preferred: none
           |                          allowed: 2g, 3g; preferred: 3g
           |                          allowed: 2g, 3g; preferred: 2g
           |                          allowed: 2g, 4g; preferred: 4g
           |                          allowed: 2g, 4g; preferred: 2g
           |                          allowed: 3g, 4g; preferred: 4g
           |                          allowed: 3g, 4g; preferred: 3g
           |                          allowed: 2g, 3g, 4g; preferred: 4g
           |                          allowed: 2g, 3g, 4g; preferred: 3g
           |                          allowed: 2g, 3g, 4g; preferred: 2g
           |                 current: allowed: 2g, 3g, 4g; preferred: 4g
  -----------------------------------
  Bands    |               supported: egsm, dcs, pcs, g850, utran-1, utran-5, utran-8, utran-2, 
           |                          eutran-1, eutran-2, eutran-3, eutran-5, eutran-7, eutran-8, 
           |                          eutran-20, eutran-38, eutran-40, eutran-41
           |                 current: egsm, dcs, pcs, g850, utran-1, utran-5, utran-8, utran-2, 
           |                          eutran-1, eutran-2, eutran-3, eutran-5, eutran-7, eutran-8, 
           |                          eutran-20, eutran-38, eutran-40, eutran-41
  -----------------------------------
  IP       |               supported: ipv4, ipv6, ipv4v6
  -----------------------------------
  3GPP     |                    imei: […]81
           |           enabled locks: fixed-dialing
           |             operator id: 22801
           |            registration: idle
  -----------------------------------
  3GPP EPS |    ue mode of operation: csps-1
           |  initial bearer ip type: ipv4v6
  -----------------------------------
  SIM      |        primary sim path: /org/freedesktop/ModemManager1/SIM/0
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it show bars gsm signals?

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Set 4G only in your settings app, disable and re-enable data, what is the rezsult? Can you send screenshots of the Settings > Mobile?

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@carlosgonz yes. Sometimes there’s a “4G” indicator as well, but I still can’t access websites without wi-fi

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@nerd7473 no difference (before, it was 2G, 3G, 4G (preferred))

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Show a screenshot of APN

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Also a picture of Modem and Network if yuou can.

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8

For internet on GSM it needed a Carrier APN, check about.
For calls make sure to config to: 4g,3g,2g. Not only 4g.

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Wait they were using GSM?

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Most countries have disabled GSM

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Thank you for the messages, I really appreciate it. Here are some more screenshots:

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“Network” screen: normally it stubbornly reverts to “Automatic” which I don’t like because that means connecting to antennas across the border without my knowledge, and then I have to pay roaming charges. Anyway that’s not the topic here. When I disable “Automatic” it is able to see available networks:
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but then when I click “Set”, after a while it says something timed out:
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(Yet for some reason it shows the “4G” indicator in the status bar, although it is not connected at all!)

My feeling at this point is that it is able to receive signals but not send them, which would explain that it can see the modem, sim card, signal strength, available networks, but can’t join any because that involves sending data.

So I think I need to re-disassemble the whole thing and triple-check all antennas, right?

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Right. It seems the modem is recognized but not networks which would indicate that there may be something with the cables (either not connected right or broken). For networks and connection strengths I’d use the relevant AT commands via terminal to get the more technical info (instead of what the modem prefers, the info of what the modem gets), see: Librem 5, Cellular Network Testing - #8 by irvinewade

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I dont think there is a hardware issues, enable to ‘Automatic’ the network, looks it is disabled on screenshoots. Then reboot.

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It was “automatic” before but I don’t like that because I don’t want my phone to decide to enter expensive roaming without asking me. It wasn’t working on “Automatic”. Also I disabled automatic network selection to demonstrate that it is able to see which networks are available.

BREAKING NEWS, my phone’s mobile connection is occasionally (like 50% of the time) working, although I didn’t do anything
Maybe the antenna cable jumps in and out its socket or something,when I walk around :thinking:

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Automatic selection does not effect roaming. It automatically selects the network level (4g-3g-2g) that your provider has available. Roaming means that you are abroad or somewhere that your provider doesn’t have coverage and then use some other network to connect to your providers services for phone, sms and data. Selecting automatic in network mode is safe. It’s just trying to provide you best service level.

There is a separate setting to prevent using data when roaming and you can prevent roaming in mobile network setting by selecting network not to be selected automatically (–> manual selection from a list that is based on the ones that the phone can discover at that moment).

Jumping is possible, at least in theory, but it may also be possible that your location indoors and relative to the base station is also interfering with the connection. There are other external factors of surroundings too. It’s hard to tell based on what we know - something to consider. We can’t compare to other cell phones as it seems (as far as I can tell from my own experience and some comments) that L5 is not quite up to par with how good it’s antennas are and may drop connection more easily in come cases. Only if the difference is significant to you previous experiences with your same L5 with the old modem in the same environment can you draw any meaningful conclusions (is that the case?). Besides jumping, some other bad connection may be the culprit - like the wires going bad (from bending etc.).

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Automatic is fine. Have never heard of salt.

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Swiss?

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Hi @JR-Fi, thank you for your message, but I’ve lost actual money because of this (mis-)feature and so, no, it’s not safe at all. There are places that are very much inside my country (although close to the border) but where my operator has no or insufficient coverage, however antennas from other providers across the border are in range (I think my country has stricter rules for permitted antenna power, which is why my phone is able to reach the antenna from abroad). So when that happens, my phone connects to the foreign operator, and if I happen to receive a text message or a call, I will be charged roaming charges. (I have indeed disabled data while roaming). I have attempted manually selecting my provider’s network, but that setting does not persist across reboots, and is quite cumbersome to select, as I have to wait for the provider list to get populated every time I want to re-select my provider from the list. So I gave up on that and try to just remember engaging the mobile connection kill switch when I’m about to enter those dead zones.

(And anyway now the modem doesn’t work so at least I’m not having that problem anymore :sweat_smile: )

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Yes, Salt is a Swiss mobile provider.

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Do they only offer 4G connection?

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