pipo m7pro wifi disconnections : definitive hardware fix

[raxy]

Hi,
my brand new pipo m7 pro suffered, after a few weeks, of random and very annoying disconnections.

I have many connected wifi device at home but the pipo m7p was the only one which was unstable connecting to my router.
Symptom = connections still ok but no response to requests and after a while, disconnection !

First thing I've tried : change my router (it was using WPA2 encryption);
I decided to use the wifi function of my ADSL box (freebox HD, I live in France) instead; encryption = WPA (too bad as not wpa2 ability for that shit).

Results : nothing changed, I decided to keep that WLAN config anyway.

Next try :
alternative ROMS; I opted for Riley's 2.1.1
Results : nothing changed.

Then I've tried RR 2.3 then 2.4 but I ended reverting to kernel 2.1.1 associated to ROM 2.4 because this was for me the more stable combination.

Results : nothing changed.

Then I tried a couple of automatic reconnections apk : wifi tx power 0.7b, and wifi fixer 1.0.1
Results : not better.

I was desperate and a friend suggested to try a hardware fix of the antenna.

I did not find any teardown photos nor videos for this tablet and was not very comfortable to open it, but I did it anyway after I've retrieved a couple of appropriate opening tools (used in the past for replacing an iPod battery) that I think are better than credit cards for that job.

So here is the photo of the opened beast to begin with



ths small black piece on the left is the combo buttons (power and esc) that has fallen down once the back was dismounted.

[manao]

Thanks. I'm waiting for your next photos.

[raxy]

Here is a photo of the inside



Please note that the wifi stuff in in the lower left ;
I think that the wifi chip is marked with a red check; compared to a M9 tablet, there is no metal shield on top of this chip even if the board has holes for such a shield. I do not know if this was the real engineer's spec...
I guess the long black (coax) wire is for the GPS; the S shaped shorter one is for WiFi.

[raxy]

reserved

Next photo : zoom in lower right part of previous photo;
I think this is not related to wifi, but I show it for the record, someone could one day find it useful once it is identified.

[giouncino]

the chip with the red check is responsible for: wifi - bluetooth and GPS
on M6pro also this chip is uncovered.
Probably your wi-fi coax is in short ciruit somewhere probably where it is soldered on the motherboard or on the antenna side.
Try resolder it again, but pay attention: wi-fi antenna (the same antenna is shared with bluetooth) is delicated. I destroyed it during resoldering.
It is poor quality also.
I ordered a replacement one coming from an iPad mini. I'm still waiting it...
I will change the 3G antenna too.

In such a way with higher gain antennas I can reduce TX power to save battery. Replacement antennas cost is ridiculous (2-3€).

[raxy]

photo of the mother board around the connectors :


from left to right :
- wifi chip
- void (probably for SIM card reader, in the 3G version)
- µSD card socket
- 3.5mm jack connector (lower), CODEC chip (upper)
- reset button (lower), flash LED (upper),
- camera and its ribbon cable and its "jdk" connector

[raxy]

Here is a zoomed view of the wifi area,



Focusing on the wifi antenna : we can found, form upper layer to deeper layer,
- kapton tape
- S shaped antenna coax cable
- metallic adhesive sticked north to the metallic chassis of the back of the LCD display,
sticked south on the antenna (rounded L shaped black platic in the lower left)
- front black plastic panel of the tablet

This configuration is not the same as the M9, so I had to think of something different to do in my case.

So I removed all these layers one after the other to see what was going on ...

[raxy]

Once the kapton was removed, I've begun to remove the metallic adhesive small rectangulal sheet.


We can see the naked copper it is attached to on the "back" of the antenna.

Clearly, "extending" the antenna to the LCD chassis; I thought this is a no go and decided to try to enhance the configuration in that area.

[raxy]

wifi antenna : front side

After having very carefully unsticked the black L shaped antenna (I could have used an hair dryier to soften the adhesive but it was around midnight and did not want to disturb the asleeped wife),
here is how it look like from "under". Note the bizarre shape of the "folded" dipole; does this shit really work; I've seen "better shaped" flat wifi antennas elsewhere...




we can distinguish the two solder points; as I was not about to change it to better performing one (this could be a further hack), I've just moved it souther (on the photo) that it was before; did not use additional glue in that step.

[raxy]

antenna redone "right"

Then I put the pieces back in place,
this time isolating the LCD back chassis with some kapton tape which also covers the wifi combo chip.



for now, the rectangular small metallic adhesive sheet is off, and the antenna re sticked farther south from the LCD back chassis.

[raxy]

final situation

Her comes my personnal touch for this reassembly :
I was not sure it'll make any difference but I wanted to restick the rectangle turned 90° and moved to the WEST as I did not want to modify (cut) it to fit better its new position :



To finish with,
I did add a few pieces of adhesive transparent tape on top of the whole thing and under the S shaped coax cable.

Than it was time to do some testing.

To sum up :
my wifi is back from hell and now works as I expect !

I was so happy that I watched as much as videos as I could until very early in the morning, and all the problems never reappeared during this hours long test sesssion.

I've no more photos to show but I think the situation has become much more normal on the wifi side for this king of the hill tablet !

thanks for reading, and feel free to comment.

[manao]

Well done !

[giouncino]

What is definitely changed is that you now have isolated the antenna from the back of the display (ground)...isn't it?

I think that it is STILL a real bad quality antenna and the best to do is changes it with a better one in such a way to reduce wi-fi/BT TX power...

[raxy]

What is definitely changed is that you now have isolated the antenna from the back of the display (ground)...isn't it?

I think that it is STILL a real bad quality antenna and the best to do is changes it with a better one in such a way to reduce wi-fi/BT TX power...

You are right,

Please give url of compatible antenna and a procedure to evaluate with numbers how good an antenna is in the context of a tablet.

[giouncino]

I'm waiting for my new one,
I'll make some tests and give you back the results.

I bought a Wi-fi / BT antenna of iPad Mini.

Changing coax cable with low loss one didn't improve signal quality. So cable doesn't seems the real problem.

The antenna is a bad quality one first of all because I easily destroyed it with a resoldering.
Second thing is that if you use command "iwconfig" you can read that the wi-fi module is configured at 32dBm AND maximum reception distance is not good at all.

Without the wifi antenna the signal reception decreased but not that much as I could think.