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TouchPad Touchstone Teardown
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Old 10/13/2012, 04:52 PM   #1 (permalink)
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Ok, I'm doing a little project which requires modifying a Touchstone charger, which means I needed to disassemble one. It turns out that it's pretty easy (although it took me acting like a chimp with an iPhone to figure out the easy way).

What you need to begin with is:

#00 philips head screwdriver
#1 philips head screwdriver
A couple of little levers (I used two small flat head screwdrivers but plastic spudgers would be best)

Here we have our Touchstone



Step 1: Remove the cable cover

Flip that Touchstone over and there's a plastic cover with the HP logo on



You'll need the levers to pry this up, there are two clips each side



You can see two of them here, the other two are the same dimensions on the other side. It's a matter of gently prying until it pops up. It's relatively robust but take care anyway.

So with the cover off...



...you can lift the cable clear of it's retaining slot. Again, take care moving the cable about as you're bending it very close to the solder points.



Step 2: Remove lower panel

See that rubber strip on the bottom? Peel that up (it's possible to save this rather than tear it like I did) and it'll reveal 4 screws.



These are #00 size and remove easily. Once that's done, poke a screwdriver through the holes and the lower panel will be pushed out. So you now have this...



Step 3: Removing the back

On the back you'll remember the two big screws, these are #1 size, so go ahead and remove them, like so...



To seperate the two parts, you hold the Touchstone in one hand and pull down on the black bump where the hinges are mounted. It should now slide apart.

Lift the back up and feed the cable through and you get to this stage (back on the left, front on the right)



And you're done. Refitting is everything in reverse.
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Old 10/14/2012, 09:56 AM   #2 (permalink)
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So how are you 'modifying' it - and why?

Keen to know!

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Old 10/14/2012, 04:31 PM   #3 (permalink)
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So how are you 'modifying' it - and why?

Keen to know!

You'll have to wait n see (hopefully by the end of the month)
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Old 10/14/2012, 04:38 PM   #4 (permalink)
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Just wondering, what's on the other side of the copper foil?
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Old 10/15/2012, 05:49 AM   #5 (permalink)
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I didn't look under it (don't need to just yet) but have seen a pic of what there is, and it's a coil. The foil is part of the charging system so I didn't want to disturb it too much.

UPDATE: Just played around some more and will be updating this thread with pics soon
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Last edited by webOSnomad; 10/15/2012 at 09:48 AM. Reason: Updating info
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Old 10/15/2012, 11:52 AM   #6 (permalink)
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Ok, so the project finally required me to strip the Touchstone down to it's components, now I can finish off the teardown. No steps on this because this is where things are either irreversible or not, strictly speaking, a good idea.

First I cut the top wire going to the copper sheet which meant I could lift up the circuit board.



Then I cut the four wires which go to the coil, freeing the circuit board. As you can see, the the wires are cut down into two thick bundled copper, and two thin single strand copper.



PCB out the way, this is what's left.



You can peel off the copper sheet as it's only stuck down and not connected to anything else.



That leaves the coil, glued into place



Looking at it, not sure what the grey stuff is, possibly insulation, it cracked as I was taking it out but it's all held together with plastic sheets glued on the back. On the front, the outer portion of the coil is made up of the single strand copper wire, the rest of it is made up of the bundled wire.

And that's what goes into a Touchstone.
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Old 10/15/2012, 11:53 AM   #7 (permalink)
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Oh, and yes, I'm going to try rebuilding the unit to see if it still works, although I'll be modifying the whole thing a fair bit for the project it's for.
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Old 10/15/2012, 02:17 PM   #8 (permalink)
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The single strand copper wire should be the Touch to Share coil, and the heavy wired coil is the inductive charger. I believe the copper foil is a shield. There is a similar one between the coils and battery on the phone's Touchstone.
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Old 10/15/2012, 07:47 PM   #9 (permalink)
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Ahh, interesting, cheers dkirker. Just wondering, is the TTS coil what lets the TouchPad differentiate between Touchstones? If the copper sheet is a shield then why would it be wired to the PCB (single cable)? Just seems a bit curious to me
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Old 10/16/2012, 02:18 PM   #10 (permalink)
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Originally Posted by webOSnomad View Post
Ahh, interesting, cheers dkirker. Just wondering, is the TTS coil what lets the TouchPad differentiate between Touchstones? If the copper sheet is a shield then why would it be wired to the PCB (single cable)? Just seems a bit curious to me
Yeah, the TTS coil should be what differentiates them. The Touchstone coil just charges, I believe.

As for the shielding... Do you have a close up shot of the PCB with the solder joint that was going to the shield? I wonder if it might be some sort of grounding? I can't really think of any other function.
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Old 10/16/2012, 02:27 PM   #11 (permalink)
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Ahh, interesting, cheers dkirker. Just wondering, is the TTS coil what lets the TouchPad differentiate between Touchstones?
Location awareness was the intended use for the "smart" TouchStones. There was also a possibility of doing data transfer, albeit quite slowly....
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Old 10/16/2012, 02:52 PM   #12 (permalink)
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Yeah, the TTS coil should be what differentiates them. The Touchstone coil just charges, I believe.

As for the shielding... Do you have a close up shot of the PCB with the solder joint that was going to the shield? I wonder if it might be some sort of grounding? I can't really think of any other function.
I haven't atm, will try to get pics sorted soon.
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Old 10/17/2012, 10:55 AM   #13 (permalink)
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Quote:
Originally Posted by dkirker View Post
Yeah, the TTS coil should be what differentiates them. The Touchstone coil just charges, I believe.

As for the shielding... Do you have a close up shot of the PCB with the solder joint that was going to the shield? I wonder if it might be some sort of grounding? I can't really think of any other function.
I believe the Touchstone Coils emit a fairly high frequency (Ghz) EM field.
A grounded copper shield would limit extraneous/damaging HF emissions?

~*~
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Old 12/25/2012, 11:24 PM   #14 (permalink)
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Originally Posted by webOSnomad View Post
Step 1: Remove the cable cover

Flip that Touchstone over and there's a plastic cover with the HP logo on

You'll need the levers to pry this up, there are two clips each side

You can see two of them here, the other two are the same dimensions on the other side. It's a matter of gently prying until it pops up. It's relatively robust but take care anyway.
I found the easiest way to get this cover off was (using the first picture as a reference) to start at the right hand side, near the top, where the cover wraps around the hinge next to the two big screws (this is the left hand top corner in the second picture). Insert the spudger between the cover and the right-hand side hinge, and pry the edge of towards the top of the touchstone. Keep prying from right to left, and the two top clips will come away. After the top clips are released, the top of the cover comes away from the back of the touchstone, and the bottom two clips are released easily by just pulling the cover downwards.

-- Rod
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Old 12/26/2012, 06:54 PM   #15 (permalink)
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Here's my extension of this mod:



-- Rod
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Old 12/28/2012, 05:09 PM   #16 (permalink)
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will that be used to trickle charge the nexus 7?
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Old 12/28/2012, 05:12 PM   #17 (permalink)
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will that be used to trickle charge the nexus 7?
Yep, after I got a couple more phone touchstone backs from the US, I found out that some put out a slightly higher voltage than others, so I used one of the higher-voltage ones there and then removed the second coil.

Seems to charge nicely on one coil now.

-- Rod
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