Unlike the SIM800L I have experience with, a SIM7670G core board I’m testing stops responding to commands via UART and to incoming SMS messages after operating perfectly for a few hours, and definitely overnight. The odd thing is, when the SIM7670G core board is connected by USB to a PC(and monitored in Putty or without Putty running) during multi-day tests, it does not fail.

4GLTEcb.jpg

This is not occurring with a SIM7600NA core board I’m also testing, it maintains a persistent connection to the 4G LTE network and never fails.

Both boards are being tested with 9VDC 3 amp power adapters, with a 470uf cap in parallel.

Why might this SIM7670G board need the USB connected to a power source? Not getting any specific support from the supplier.

Could it just be a defective board?
Has anyone else experienced this?