Thanks! It looks like you have a different network module - is yours 2G? Mine is 4G.
I happen to have a 2G main board and a 4G main board in hand.
On the 2G main board, none of those pins are bridged.
On the 4G main board, the 6th and 7th pins from the top of the socket are definitely and quite obviously bridged; the 8th, 9th, and 10th pins also appear to be bridged, though more subtly - closer to the socket itself and with a thinner trace.
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Very helpful, thank you! I can stop worrying about that now, it’s not the cause of my problem…
So looking at the schematics, it all makes sense. Pins 41 and 39 (6th and 7th pins from the top) are both VSIM, so it doesn’t matter whether they are bridged or not; and pins 37, 35, and 33 (8th, 9th, and 10th pins from the top) are all GND, so it doesn’t matter whether they are bridged or not! I suspect the bridging on the 4G main board may be because of the higher current draw of the 4G module.
I have a module plugged into the socket on my 4G board, so it’s impossible for me to see the 26 traces (even numbered pins) on the other side of the board, but on the 2G board none of those are bridged either.
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Question for the Circuitmess staff: is the main board schematic for the 2G main board or the 4G main board? I ask because it was pointed out to me (and I can now see) that there are additional components just south of the network module on the 4G board, but I don’t know if those are shown on the schematic. You can see these in wbp’s photo above.
Hey guys,
Yes, it’s normal that those pins are briged on the 4G board.
We’re very happy for you guys, this is what this forum is all about, sharing ideas and helping each other work through any issue. Thank you for being such a big part of the forum!
@frankprindle Yes, the 4G schematic is not online, just the 2G. Thanks for pointing that out, it’s cool that you’re so interested in our designs and tiny details, we’ll put it up online and i’ll leave a link here as soon as we do.
So even the main board differs, I thought it was only the actual network card that differed.
Thanks Robert - I’ll do a comparison when I get a chance.
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Yes,
The main board is different and that means that 2G and 4G modules can’t be used on the same set.
Are you planing to release the schematics of the 4G network card as well?
I have now compared the two main board schematics found on github (commit dated 6 nov 2019 68859a0d1c898e0ede13fd29130420f4dc8f387a)
i.e. MAKERphone-main-board-4G-schematics.pdf and MAKERphone-main-board-schematics.pdf
But besides different image resolution, some moved labels and other small cleanup, I can’t find any real differences between those files.
Are you (@robertCM ) sure that they are the correct ones, since your said that there are supposed to be different.
If so, what are the differences that I missed?
Curious!
I haven’t had a chance to compare the schematics yet, but I know for sure that the physical 4G main board has quite a number of additional components located just below the network board when compared to the 2G main board. I expected those components to be shown on the 4G schematic. I’ll try to review it tomorrow.
Yea, I can see that now on the photos above. The 8-pin chip is an TC8002D (audio amplifier) on my card, and it is drawn on both the main board schematics I referred to earlier (to the far right)
So either has that part moved to another location on the board between 2G and 4G boards, or are both schematics actually the 4G schematics.
Blixten, I eyeballed both schematics and it seems you are right (unless the differences are extremely subtle). Other than reorienting symbols, moving things around, and using slightly different fonts so that the 4G schematic is considerably less readable (lots of text on top of symbols), there seems to be no substantive difference between them. But I have been assured that the main boards are different and the 2G main board can only work with a 2G module, and a 4G main board can only work with a 4G module, and the 4G main board has extra components. So something is amiss for sure.
Hey guys,
Yes, it seems that there has been an error. The 4G schematics was up all along. 
Now we’ve added the 2G schematics, which you’re going to recognise by not having some of the components in the right upper part of the scheme.
All the schemes -> https://github.com/CircuitMess/CircuitMess-Ringo/tree/master/schematics
Also about the 4G network card - that was not produced by us and we do not own the schematics. However, here are some documentation we have found from SIMCOM.
I hope you can find here whatever it is you need -> https://campuscrm.campuscomponent.com/images/Product_Pdf/SIM7600CE_SIM7600C-PCIE_Hardware_Design_V1.00.pdf
Sorry for the mess up, it should be all good now! 
Cheers,
Robert
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So at the very least then, the 2G board drives the speaker directly, while the 4G board may drive it directly or through an audio amplifier, depending on the solder jumpers selected. Is that perhaps the difference between the 4G modules with the “-H” at the end and those without?
There may be other main board differences also… I haven’t checked in detail (but will unless Blixten beats me to it 
).
-H means high speed and the modules marked that way have higher cellular data speed capabilities
This does not affect the main function of the module in your MAKERphone and all -H and non -H modules were tested in the appropriate geographical regions where we send them
Hope this helps and good luck with your future work 
Ok, then just let’s say that the 4G module may or may not be able to drive the speaker without an amplifier, while the 2G module never needs an amplifier. That is difference #1.
In addition, I see a 1.5K resistor to GND from pin 2 of U1.1 (level converter) on the 4G board that is not on the 2G board. This is part of the serial interface between the brain board and the network module. I don’t know what function DTR plays here or why it needs to be pulled down for 4G only. This is difference #2.
That’s all that I could see, but then my eyes aren’t what they used to be.
You’re right, those are the only two differences
DTR is used for putting the network modules to sleep
SIM7600 has some special mumbo jumbo that requires it to have that resistor on DTR.
The amplifier difference is because SIM800 has the amplifier built-in whilst SIM7600 doesn’t have one. We just couldn’t make both modules work with the external amplifier and were running low on time so we’ve just branched the boards