GPRS Shield does not work

[Alex-w]

the problem is that the module can‘t find the sim card，i suggest that you’d better replace the other sim card
if the problem still exist，then you can do that
1.Bad contact SIM card and card, you can try to increase the gasket on the SIM card
2.SMT poor welding, you can use the multimeter testing module and SIM card connectivity between pads.
3.The surrounding environment with interference, confirmed the existence of super electric / magnetic field test whether around the scene, such as the high voltage transmission line, power wireless equipment,you can try to live SIM card and SIM card every signal line line using a shielding cover, or the use of shield wire processing SIM signal line, see if the problem goes away.

[bzuk]

sim card I'm trying to change for just other when it did not work, I have no home no high magnetic field nor high voltage, if that were nothing to me at home did not work, no device would not work
remains a problem only in contacts, please describe to me what I measured with a multimeter, sim card connector contacts I have to be sure the solder newly

[Alex-w]

first，set your multimeter like picture 4021
then test that does the simcard‘s pin short with sim900 pin’s or the pin‘s current limiting resistance like picture 40265

[bzuk]

You did not write exact measurement procedure, whether it should be GPRS enabled in power or off, where do I put the black and red cable multimeter, etc.

[Alex-w]

1.you shold set the multimeter like that

IMG_4021.jpg (196.73 KiB) Viewed 16409 times

2.test that the Wiring is welll

IMG_4021.jpg (196.73 KiB) Viewed 16409 times

（use red Probe）

[bzuk]

I have this multimeter

I did not know if I measure the resistance or diot,

resistance
pin30 0
pin31 182,33K
pin32 10,31M
pin33 0


diot
pin30 .0L
pin31 1,2180
pin32 1,3216
pin33 .0L

[Alex-w]

1.first，set the multimeter like this

IMG_4025.jpg (213.17 KiB) Viewed 16396 times

2.test that these signals is connected，if not，the resistance is not soldered well。

DSC_01416.jpg (112.23 KiB) Viewed 16396 times

[bzuk]

almost the same values ​​as I measured straight pins on SIM900

1 179K
2 0
3 0
4 0
5 0
6 9,998M

[Alex-w]

i don't think it's right，cuz that number 2 in sim card it ’s not connecting with sim 900 resistance between simcard pin4、5 and sim900‘pin 30、 33，and there are Not with resistance grade，but diode gear

[bzuk]

I did measure directly the SIM900 pin30-33 and I measured the same values, Therefore, I measured the resistance test between sim900 pin30 and cardconnector pin4 0,23ohm and tests show it's soldered to the well, sim900 pin33 and cardconnector pin5 21,8ohm