Teclast X98 Pro Wi-Fi Woes – A solution?

Teclast X98 Pro Wi-Fi Woes – A solution?

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This topic contains 2 replies, has 3 voices, and was last updated by  Usman N 3 years, 1 month ago.

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  • #19756

    Doug Lung
    Participant
    • Posts: 11

    I received my X98 Pro a week ago. I haven’t experienced any heat related problems, but I haven’t pushed it either, running Arch Linux in a Virtualbox (it does work!) is the most stressful thing I’ve done to it so far. The major issue I found is very poor Wi-Fi signal levels. Using the Wi-Fi Analyzer app, the signal level is 20 to 30 dB below that of my other devices and never hits all bars even two feet from my access point. I finally decided to open it up to see if I could see anything wrong.

    The X98 uses a Realtek RTL8723BS module. The data sheet is available here: http://www.ofeixin.com/data/20150108162813187.pdf

    As you can see, there is only one connector for both Bluetooth and Wi-Fi.  In my experience, turning Bluetooth on or off didn’t have any noticeable effect on the signal level.

    I think the problem is the antenna is not connected to the module! See the attached photo of the circuit board, (battery side up). The RF pin on the module (second pin from the right) in the lower left of the image goes to a filter consisting of two capacitors and an inductor, as is shown in the data sheet. It then goes through two of six pads in an array that might be for a future modem. I suspect the black “jumper” is either a low value resistor or a capacitor.  It then goes through what appears to be another “Pi” filter network filter before connecting to the antenna on the right. Notice there is no inductor or capacitor connecting the left pad to pad connected to the antenna cable! (look below the inverted “F” in the WIFI/GPS lettering).

    Carefully touching a screwdriver to the pads on the left or directly to pin 2 of the RTL module boosted the signal level by 20 dB or more! Since I didn’t have a soldering tip small enough to use on these pads or any conductive paint to jumper the pads, I decided to close the unit back up. I did clean up some of the solder splatter you can see near the “W” in WIFI, but that didn’t make any difference in the signal.

    Testing with a portable Wi-Fi hotspot showed no difference in signal level as I moved the hotspot close to the antenna. Since the module is shielded by the metal case, moving it closer to that area didn’t make any difference either.

    I’d be interest in hearing if anyone else experiencing weak Wi-Fi has a missing component in their X98 Pro? I suspect it fell off when someone at the factory was soldering the coax to the board in final assembly.

    I’ll report back when I have a way to jumper the gap. I suspect it will make a huge improvement in Wi-Fi performance!

    …Doug

     

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    #19761

    Hualalai
    Participant
    • Posts: 126

    I see another possibility.  The gap under the F of WIFI is an inline component in an inner layer of the multilayer PCB.  The boost in dB from the “screwdriver test” was antenna gain… but in what band?  Could have been your local AM station.  You can test your theory with a trimmed paperclip jumper with L ends.  Lay some electrical tape on the PCB, then put the trimmed paperclip jumper in place.  I predict no improvement in your wifi performance.

    Touch a 20 cm straight wire to pin 2 of the Realtek chip and see what happens to your wifi bars.  The core (assuming an antenna coax cable) of the RF antenna connection on the Realtek wifi/BT chip is pin 2.   Coax braid to ground.   (see page 11 of the spec sheet in your link).

    I would solder a coax pigtail terminated in the usual wifi RF connector to the Realtek chip.  You then connect a stock wifi antenna (USD 5 on eBay) for tablets to the connector.  Page 10 of the spec sheet has a pix of the Realtek chip.   That would be a great mod… that I’ve never seen done before.

    #31797

    Usman N
    Participant
    • Posts: 4

    Did you manage to fix the weak signal?

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