Modem shield
#1
Question 
My PinePhone has massive modem issues. It resets even when sitting on the table doing basically nothing, not even transmitting lots of data. On some days I have to restart it every ten minutes or so, on others it can be stable for hours. The crashes appear to be pretty random.

So this evening out of boredom and because I’ve nothing to lose, I opened the device. One of the FFCs sat a bit loose in the connector, the one right next to the SIM card slot. Maybe that was a reason, although I'm not sure whether that FFC goes to the modem. A quick look at the schematics didn't tell me anything.

Also, I pried the shield off the modem:
   

Here I have some questions:
  • These two fat blobs of thermal paste bridge a gap of almost a millimeter! Can that thermally even work?
  • Can I operate the modem without the shield?
  • How would that impact performance or thermals?

About the phone:
  • UBports Edition with VCONN fix (desoldering, no replacement)
  • ADSP 01.003
  • Biktorgj firmware 0.4.2 (should certainly try 0.4.5-2)
  • postmarketOS Edge / SXMO

PS: My PinePhone Pro has already arrived in Berlin, but it’s stuck in customs, and communicating with DHL Express is problematic due to the modem crashes. So I almost have a deadlock situation here.  Cry
  Reply
#2
It depends on the thermal paste, but I guess they picked one that's suitable for the job. Even thick thermal paste conducts better than an air gap. Similarly the thin steel shield isn't an ideal heat spreader but is better than nothing. I don't know if the shield is there to keep RF out or in, but operating without it probably counts as modification which licensing authorities don't usually like.
  Reply
#3
(12-13-2021, 07:11 AM)wibble Wrote: It depends on the thermal paste, but I guess they picked one that's suitable for the job. Even thick thermal paste conducts better than an air gap. Similarly the thin steel shield isn't an ideal heat spreader but is better than nothing. I don't know if the shield is there to keep RF out or in, but operating without it probably counts as modification which licensing authorities don't usually like.

To be fair the harmonics it might radiate are in the mW rance and dissipate quickly.
FWIW I have never seen or heard of anyone getting their phone explored by regulators, even most pirate radio is ignored.
  Reply
#4
Thanks for the explanations I also opened a thread in the Quectel forums, and I was informed that "With the shielding cover, the module radio frequency can be protected from external interference".
  Reply


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