Cellular module: 1000uF cap on power? Solve anything?

As soon as I’ve determined the problem just soldered a connector for the PSU right on the GSM board.
Think about the design I believe that despite the power socket for the board has 5V the wire gauge for the cable will have trouble carrying the required juice for those bursts…
I suspect that when the module starts those power peaks the voltage drop on the 5V wire may be just too much and that causes the Vin of the LDO to drop bellow the required minimum and it fails.
Maybe there is nothing wrong the GSM module design in what concerns the power supply and capacitors… Haven’t tested it, just hacked the power supply to get mine working! :slight_smile:

@ JSimoes - Can you provide a close-up of your soldering? Not sure where to attach it…

Here it is. Note that I’ve a second wire to connect GND too.

Thank you so much. What voltage will that be able to handle?

You’re welcome! :slight_smile:
SIM900 power supply ranges from 3.2V to 4.8V. I’m using 3.3V.

Would it make sense to place a thick wire from the 5V output of the USB-DP module to the Cellular module?

If the wire is too thin (as I believe it is) then yes, replacing it would help.
But that won’t be easy as you need to also replace the cable from the USB-DP to the main board and the next one from the main board to the cellular module.
Changing a single wire in a flat cable with such a small pitch can be challenging…

Don’t guess… Measure.

you can either measure, calculate or even look up on the data sheet the resistance of the wire. Do this and use ohms law to calculate the sort of voltage drop you might get.