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Modem on OVMS-33-7600G change?

Hi everyone

I just bought a new OVMS system from a 2023 batch (OVMS-33-7600G) and faced the issue that I was not able to use the SIM card (Swiss SIM) that I have been using in another OVMS-33-7600G device that I own from an earlier 2021 batch.

When I have the SIM inserted, when booting, the modem's blue light quickly flashes up and then shuts down again and in the console the modem module stays iterating in the timeout loop. During the loop the blue light quickly flashes up every ~10-20s. When I use the hologram SIM everything works fine.

As said, with another OVMS system (also OVMS-33-7600G) it does work and I have copied all configs from that OVMS device. Also I have double checked whether the APN is set correctly.


First of all: Did the hardware change? (It seems like the same modem?)

And what could be another problem based on SIM connection? It seems weird to me that the modem directly shuts off after the launch.

Is there a new restriction on SIM? (e.g. does it need a PIN?)


Thanks a lot for the help!


markwj's picture
Should be no changes.

Should be no changes.

I suggest you connect via USB and have a look at the logs to see the reason for the problem.

Issue was power supply

I was able to track down the problem. So it was not the SIM causing the problem. As soon as I registered the Hologram SIM it had the same effect.

Eventually I figured out that the problem was the power supply. It seems like the new SIM7600 module has a bigger power draw during connection setup that overloaded the voltage converter during that time and reset the modem due to brownout.

With a 12V supply it works well. (And a better USB supply as well, but not reliably)

markwj's picture
Thanks for the feedback. Yes,

Thanks for the feedback. Yes, OVMS v3 (with 4G) does require more power, and typically either a good USB v3, powered hub, or 12V supply. See here for more info on this:


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