Sim card destroyed twice by router

Hardware Questions and Recommendations
1

Hello
Twice I had a defect Sim Card in the last 3 Weeks with my D-Link DWR-921 Router.
Because of traveling I stored the first Sim Card in a plastic bag for use with my mobile Router.
Home again I restored the Sim Card in my DWR-921 without connection to the Internet.
I recognized some sticky dirt on the Sim Card and removed it. The same on the card connector.
After it, I got Internet connection, but a few days later suddenly the connection drops.
The Router toggled between connection and disconnect, regardless what I tried. I restored the OEM Firmware (openwrt-19.07.6-ramips-mt7620-dlink_dwr-921-c3-squashfs-sysupgrade I used before), the same behavior. Even another Router and Smartphone wasn't working with this Sim. Calling the Helpline from that Sim card, a automatically answer says; there is a a problem with my Sim Card.

Calling the Helpline from another line, all the hints doesn't help and finally renewed the Sim Card.
The Problem was solved, for the moment.
But 2 Weeks later, the same behavior came up, the router app shows connection toggling (still OEM SW).

Again, Sim card renew solved the Problem.

My question; Has anyone seen the same behavior, or explanation for this? For me it seems the Router write some wrong data to the Sim card. And is there a solution? I'm unhappy to dispose the DWR-921, I would like to flash openwrt 21.xx.

Thank you

2

Sounds like defective hardware to me.

The router can't be writing wrong data to the sim card, but it could be sending wrong voltage.

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3

Or the sticky sim has contaminated the sim slot

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4

That's what I first thought, but cleaning didn't help.

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from www.manualslib.com
how may this happen?
Thank you

5

First you should check if the power supply is providing the correct voltage.
Then with a multimeter test the CCVCC, as there are 1,8 , 3, and 5 volt options.

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6

Hello trendy
Voltage supply is 12 Volt - correct value, at the Sim Card I get 1.8 Volt on one Pin, I don't know the number, because I can only measure on the board, bacause of Sim card connector housing

7

Seems correct, however there might be some spikes of higher voltage, hence the fact that it does work for some time, then it stops.

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8

My intention to discuss here was the hope to find someone who has made the same experience or has deeper knowlege into the handshaking between sim card and router.
Wether I have to open the sim connector case for cleaning und take the risk to kill a third sim card or dispose the router.

9

Priority #1:Make sure that there is no sticky dirt on the SIM card slot contacts, otherwise all other activities will be doomed.

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10

Thank you all for your hints, in the next days I'll remove the housing (soldered) clean all 6 connections and make another attempt.
Strange, that no other made the same experience, I searched the net for it.
Thanks for your attention.

11

Worth mentioning here that this is not a good way to store a SIM card. Although they are pretty robust, SIM cards can still suffer damage from ESD, and plastic bags are potential sources of static build-up. If your card was damaged, it could explain the first failure you saw. It is even possible (although not terribly likely) that ESD damage to a SIM card could cascade to cause issues with the device using that card (i.e. the DWR-921), which could then cause damage to future cards... kind of like the famous 'click of death' that happened with Zip drives back in the day.

In the future, you should get a proper case or ESD safe bag for storing your SIMs while in transit.

To be clear, I am not saying that this is absolutely the cause of your issues, but it is one possible explanation.

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