SIM340DZ spontaneous reset + can't change band

Hello everybody…

I’ve been years working with sim200, sim300 and sim340dz… But now I’m facing a problem.

I’m having some troubles with sim340DZ… It was working just fine… perfectly fine… Then one day it begins to reset itself after call ready is issued…

RDY

+CFUN: 1

+CPIN: READY

Call Ready

[10 seg after]

RDY

+CFUN: 1

+CPIN: READY

Call Ready

and so on… all day… It seems it resets when trying to register to the network…

  • I allready check the power supply with oscilloscope… it remains steady…

  • I’ve read in other post that it could be a BAND issue… they were having the same problem, change band and then it work fine. I’m having 2 problems whith band…

No matter if I have the SIM card inserted or not I get this errors:

  1. When trying to get band AT+CBAND? I get no reply from module… it seems like it crush… until it reset itself… If I input ANY other command module replys ok, but since I send the band command no matter what else I input from now it won’t reply anything. Command is spell ok I check that.

  2. When tryng to set band… I get +CME ERROR: 769 —> Can’t get control of request module…

One curious thing is that I hear a noise on the board (the same noise you hear when you put your cellphone near a speaker and you’re recieving/transmitting data, the interference noise) I guess the noise is at the coil of the power supply (it’s a switching type)… put some caps and now no noise…

Any help would be greatly appreciatted