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GPS Antenna Contacts

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jhovak
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Default GPS Antenna Contacts

I’ve been struggling with why my GPS quit seeing any satellites after the 9.4.2.11 update when I realized something looking at Anand’s teardown:

AnandTech - ASUS Eee Pad Transformer Prime Teardown

Perhaps the antenna connections are weak or have become slightly corroded. Based on his teardown the contacts are spring type “pogopins” which mate with the opposite face. With that thought in mind I decided to try and flex the tablet ever so slightly to clean the contacts. The idea being that the slight flex would cause the pins to scrape the contact surface rubbing a clean(er) spot.

Before the 9.4.2.11 update I had the typical poor performance from the GPS, getting locks but losing them on the move. I had given up on it [GPS] until this update which touted GPS improvements. After updating and wiping I tested the GPS again, but could not see even one satellite after letting it sit, more than once, for over an hour with Wi-Fi on and off.

I must stress I strongly suggest you do not try this on your tablet for fear of damaging it. I take no responsibly for damage to anyone’s tablet and am only reporting my actions.

After this procedure I am able to see several birds indoors, albeit with weak SNR. This has me convinced that part of the problem is related to these contacts, and may serve to explain some of the weak Wi-Fi reports. It may also help illustrate why only some users are seeing issues, and perhaps why some of the returns are functioning better. These contacts may be more robust in some units or possibly be able to be rectified via service.

I do understand there are other factors related to both the GPS and Wi-Fi, but this appears, at least to me, to be part of the bigger picture.

Please note that the amount of flex I’m talking about is next to nothing, enough to see a change in light bleed around the display, I was afraid to go too far.

*Mods, I'm not sure why this post was deleted before, please PM me if there is a problem with this post. I did not include the link.*
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motocamp
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Hi jhovak,

that sounds very interesting and makes me nervous thinking of manipulating a new device. You are brave!
Do you have some pictures of your action?

Thanks.

Cheers,

René.
 
e.mote
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http://forum.xda-developers.com/show...0&postcount=10

You can bypass the pogo pins by connecting a pigtail to the UF.L connector at the chip leadouts, then solder the other end to the antennae's copper pads. It should improve reception.
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jhovak
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e.mote,

Looks like you beat me to this I never saw your post, but that's exactly my thoughts. I was able to torque it a bit to get it working again. That maye be what they are doing to get the RMAs reported to work better, "fixed".

motocamp,

Unfortunately I don't have any pictures of the process, but you wouldn't be able to see much, I only deformed the case/screen very slightly. The problem is you may end up popping other solder joints in the process.
 
yhzhrm
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Quote:
Originally Posted by jhovak View Post
I’ve been struggling with why my GPS quit seeing any satellites after the 9.4.2.11 update when I realized something looking at Anand’s teardown:

AnandTech - ASUS Eee Pad Transformer Prime Teardown

Perhaps the antenna connections are weak or have become slightly corroded. Based on his teardown the contacts are spring type “pogopins” which mate with the opposite face. With that thought in mind I decided to try and flex the tablet ever so slightly to clean the contacts. The idea being that the slight flex would cause the pins to scrape the contact surface rubbing a clean(er) spot.
I agree. Makes perfect sense to me.

Everyone has the same aluminum back, so you would expect the same results across the board (barring weather and atmospheric conditions) for all Primes. There has to be another piece to the puzzle of bad GPS performance when some user's report GPS working and getting locks and other user's reports no GPS active with no satellites seen and no locks.

Thanks e.mote for your explanation of the antena contacts. I think you hit the cause of the GPS problem. Hopefully ASUS saw your post and address this prioblem so it does not occur on their the planned 700 series.

Cheers
 
demandarin
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I forwarded all this info to Gary in a pm just recently. including details, link to that thread e.mote posted in and that teardown showing pogo pins. hopefully he will get it soon and pass info to engineers.

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http://forum.xda-developers.com/show....php?t=1409077

 
sdynak
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pardon my lack of GPS knowledge but what is considered good or bad when comparing GPS in general? This is my prime outside earlier but there were fluctuations
 
slybarman
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I am a bit more skeptical about the hardware pins as a sole cause. Reason:

I had pretty decent GPS performance until this last update which totally killed my GPS performance. This suggests to me that there is a firmware/driver type component to at least some people's problems. The same update did correct other people's problems. So perhaps there are some slight differences in the GPS chips that the firmware is not playing nice with or accounting for?
 
redpoint13
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I can confirm this at least partially works. I tried to drive home using GPS test the other day from work and could hardly get a lock especially at high speeds. I saw this and did a number of squeezes aroung the area of the GPS connector and had a significant change.

Drove home with GPS test today and I hardly ever saw it not locked, even going at 70mph, though it would go between 2 and 8 locked sats or so. Halfway through the drive I opened google maps. It took 10-15 seconds to lock, but then I watched my blue arrow follow the road exactly almost the entire way home. It only lost lock when I was stopped under an overpass at a stop light.

To be clear the signal strength is not that of my phone, but at least it's working now.
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demandarin
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Have you seen the new evidence found? It was found out that Original Transformer actually uses the soldered type connection E.mote described. I was gonna start a thread but no use as this one is perfect for the new info.

FIRST here is the quote n pics from e.mote of the current Prime type of connection

Quote:
Originally Posted by e.mote View Post
From looking at the Prime teardown, your wifi loss may be due to a loose connection. Instead of running a pigtail directly from the chip lead-out to the antenna, the Prime uses spring-loaded pogo pins (1st pic) as intermediate connectors.

Second pic shows the pogo pins for the main wifi and GPS antennae. The spring-loaded pins are pressed against the copper pads of the respective antenna (3rd pic). Suffice it to say, this isn't the most secure way to connect the antennae.

Aside from possible broken or intermittent connection, it also looks like a high-loss connection, and could contribute to attenuated signal reception. My guess is that this may be the main culprit of wifi/GPS woes, with the metal shell being a contributing factor.

The 4th pic below is a U.FL connector that's normally used for antenna pigtails. The lip has an outer overhang for a secure connection.

My guess is that the tablet was bumped and something shifted a bit, breaking the antenna connection.

This is FYI only, as the unit isn't user-serviceable. It does look like a simple fix, but you'd have to open the unit. Edit: You can try smacking the top edge of the tablet a few times and see if it will jar back into place. Worth a try.


Pogo pins used as intermediate connectors for wifi & GPS antennae


The two pogo pins for main wifi and GPS. The spring-loaded heads are pressed against the antennae's pads to make the connection.


The main wifi & GPS antenna, with copper pads to connect to the pins


U.FL connector, normally used for antenna connection
NOW here is the Original Prime teardown and type of connection


http://m.techrepublic.com/photos/cra...53#photo-frame

OG Transformer teardown pix



NOW HERE IS THE KICKER
Quote:
Originally Posted by clenz View Post
that GPS/Wifi connection looks like a soldered wire and not pogo pin to me!







WHO said copy n paste n select text doesn't work well on the Prime? Lol I did this all from the Prime itself from various threads.

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Lg Optimus G Pro- new 1080P 5.5in. Display w/Snapdragon 600 Andreno 320

Microsoft Surface Pro 128gb. Full HD Display 1080P Windows 8 HD4000 Graphics Type Cover

Prime/Tegra3 Gamers Thread
http://forum.xda-developers.com/show....php?t=1409077


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