EEE PC 901: Installing a 3G modem with a switch and the ability to connect to an external PC
In this article I will tell how to remove the 3G modem inside the EEE PC 901 case, make a switch and how to connect the modem to an external PC later.
It was possible to buy a mini-PCI connector and a modem on e-Bay, but it would cost extra money and at least 2 weeks of time. I wanted to do here and now, besides, there were a couple of USB modems at hand, and there were several ideas in my head that I wanted to implement. Huawei E1750 was chosen as the test subject because of its small size and the SIM card holder built into the board.
So, under habrakat you will find detailed instructions with photos.
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1. Open the case, take out the board and remove the USB-connector.
2. We solder wires to the contact pads, which will connect the modem with a USB and a switch. For this purpose, I took a segment of the loop for FDD.
3. Now proceed to refine the switch. The store found the usual 8-pin slide switch, which was later dopilen to the desired size (width should be equal to the distance between the two fasteners on the inside of the case next to the slot under the card reader). Also, for convenience of soldering, extra contacts were removed, and the plastic slider was shortened (inside the slider there is a spring pressing a metal ball to the textolite for precise switching, when shortening, this spring is most likely to be on the surface and the ball will not be pressed anymore and, while holding this position, melt the hole in the slider).
4. Next, you need to cut a switch groove in the board so that the board fits into place when it is assembled. At this point there should have been some kind of connector, so the removal of this part of the board would not affect the operation of the laptop (the desired part of the board is highlighted in purple in the photo).
As a result, you should have something like this:
5. Cut a switch hole in the housing. In the absence of a two-position, I used a three-position switch, as a result, the inclusion of an unnecessary third position became impossible due to the size of the hole. Then glue the switch in place, I used for this ordinary rubber glue "Moment".
If the thickness of your switch is about the same as mine, then you also need to edit the cover a little.
6. Since the case is shielded inside, you will have to abandon the built-in antenna and connect the modem to the antenna located in the cover of the laptop. If you can find a strong antenna wire of small thickness, use it. I didn’t have such a wire, so an insulated copper wire from an audio cable was taken, the copper braid for soldering was stretched on the outside as a screen, and the top was covered with tape. The use of heat shrink tubing had to be abandoned due to its thickness. You probably don’t have enough space for a wire on the side of the screen, so remove the screen and run the wire along the lid of the laptop, fixing it with foil velcro, solder the screen and wire to the WiFi antenna in the same way as the cable from the WiFi module.
I understand the antennas rather superficially, so I did all this based on intuition. If anyone knows how to do better - write in the comments.
Attention!
Part of the article about the antenna is outdated, look at the new version here .
7. With the help of electrical tape, isolate the board where the modem will be located. At first there was a thought to place the modem under the back cover of the laptop for a quick change of SIM cards, but without cutting out a large enough part of the case, there was not enough space, so I decided to place the modem where the EEE PC 901GO has a mini-PCI 3G modem card. In addition, having the ability to change the tariff by connecting the modem to a PC, the need to change SIM cards is almost eliminated, especially if you consider that the megaphone network has pretty good coverage.
8. Next, you need to carefully solder the wires from the modem to the back of the USB-connector, and bring 4 contacts for soldering to the switch - DATA + and + 5V. When these contacts open, the device disconnects from the system almost painlessly. Do not forget to connect the grounding pin on the modem to the case of the USB connector on the board. From above, the modem can also be sealed with a strip of electrical tape, so that a sim card does not accidentally fall out, and just for isolation.
9. Solder the antenna to the modem (where the built-in antenna used to be), and the braid to the case of the USB connector. With the help of foam double sided tape, fix the modem on the board, I used two strips about 1 cm wide to leave a space for ventilation between them. After that, put the board back in place, solder the leads to the switch and reassemble the laptop. If you did everything correctly, there will be no problems during the build process.
That's all, as a result, we got a laptop with a built-in 3G modem, which will no longer interfere while hanging out. As a nice addition, it became possible to connect a modem to a PC (for example, to change the tariff through a megaphone Win-GUI, which is easier for an ordinary person than to deal with sending USSD requests via the command line), disconnect it to save battery power, and also use USB port when the modem is turned off.
To connect a modem to a PC, you need to insert a USB-USB cable into the corresponding port of the turned-off laptop (or assemble the adapter like in the photo and use a regular USB extension cable), switch the modem to the USB port and insert the cable into the PC.
PS After the assembly, a useful idea appeared - you could attach something like a metal pin to the switch slider, which, when the modem was turned on, would slide into the USB port and not allow anything else to be inserted into it from the outside, but with an external USB cable inserted into this port -device did not allow to turn on the modem.
It was possible to buy a mini-PCI connector and a modem on e-Bay, but it would cost extra money and at least 2 weeks of time. I wanted to do here and now, besides, there were a couple of USB modems at hand, and there were several ideas in my head that I wanted to implement. Huawei E1750 was chosen as the test subject because of its small size and the SIM card holder built into the board.
So, under habrakat you will find detailed instructions with photos.
')
1. Open the case, take out the board and remove the USB-connector.
2. We solder wires to the contact pads, which will connect the modem with a USB and a switch. For this purpose, I took a segment of the loop for FDD.
3. Now proceed to refine the switch. The store found the usual 8-pin slide switch, which was later dopilen to the desired size (width should be equal to the distance between the two fasteners on the inside of the case next to the slot under the card reader). Also, for convenience of soldering, extra contacts were removed, and the plastic slider was shortened (inside the slider there is a spring pressing a metal ball to the textolite for precise switching, when shortening, this spring is most likely to be on the surface and the ball will not be pressed anymore and, while holding this position, melt the hole in the slider).
4. Next, you need to cut a switch groove in the board so that the board fits into place when it is assembled. At this point there should have been some kind of connector, so the removal of this part of the board would not affect the operation of the laptop (the desired part of the board is highlighted in purple in the photo).
As a result, you should have something like this:
5. Cut a switch hole in the housing. In the absence of a two-position, I used a three-position switch, as a result, the inclusion of an unnecessary third position became impossible due to the size of the hole. Then glue the switch in place, I used for this ordinary rubber glue "Moment".
If the thickness of your switch is about the same as mine, then you also need to edit the cover a little.
6. Since the case is shielded inside, you will have to abandon the built-in antenna and connect the modem to the antenna located in the cover of the laptop. If you can find a strong antenna wire of small thickness, use it. I didn’t have such a wire, so an insulated copper wire from an audio cable was taken, the copper braid for soldering was stretched on the outside as a screen, and the top was covered with tape. The use of heat shrink tubing had to be abandoned due to its thickness. You probably don’t have enough space for a wire on the side of the screen, so remove the screen and run the wire along the lid of the laptop, fixing it with foil velcro, solder the screen and wire to the WiFi antenna in the same way as the cable from the WiFi module.
I understand the antennas rather superficially, so I did all this based on intuition. If anyone knows how to do better - write in the comments.
Attention!
Part of the article about the antenna is outdated, look at the new version here .
7. With the help of electrical tape, isolate the board where the modem will be located. At first there was a thought to place the modem under the back cover of the laptop for a quick change of SIM cards, but without cutting out a large enough part of the case, there was not enough space, so I decided to place the modem where the EEE PC 901GO has a mini-PCI 3G modem card. In addition, having the ability to change the tariff by connecting the modem to a PC, the need to change SIM cards is almost eliminated, especially if you consider that the megaphone network has pretty good coverage.
8. Next, you need to carefully solder the wires from the modem to the back of the USB-connector, and bring 4 contacts for soldering to the switch - DATA + and + 5V. When these contacts open, the device disconnects from the system almost painlessly. Do not forget to connect the grounding pin on the modem to the case of the USB connector on the board. From above, the modem can also be sealed with a strip of electrical tape, so that a sim card does not accidentally fall out, and just for isolation.
9. Solder the antenna to the modem (where the built-in antenna used to be), and the braid to the case of the USB connector. With the help of foam double sided tape, fix the modem on the board, I used two strips about 1 cm wide to leave a space for ventilation between them. After that, put the board back in place, solder the leads to the switch and reassemble the laptop. If you did everything correctly, there will be no problems during the build process.
That's all, as a result, we got a laptop with a built-in 3G modem, which will no longer interfere while hanging out. As a nice addition, it became possible to connect a modem to a PC (for example, to change the tariff through a megaphone Win-GUI, which is easier for an ordinary person than to deal with sending USSD requests via the command line), disconnect it to save battery power, and also use USB port when the modem is turned off.
To connect a modem to a PC, you need to insert a USB-USB cable into the corresponding port of the turned-off laptop (or assemble the adapter like in the photo and use a regular USB extension cable), switch the modem to the USB port and insert the cable into the PC.
PS After the assembly, a useful idea appeared - you could attach something like a metal pin to the switch slider, which, when the modem was turned on, would slide into the USB port and not allow anything else to be inserted into it from the outside, but with an external USB cable inserted into this port -device did not allow to turn on the modem.
Source: https://habr.com/ru/post/120914/
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