(PW2) Ripped off TX serial pad. What now?

[drgonzalez94]

Hello everyone. I've been a long time reader, but never got around to registering. I recently jailbroke my voyage via the serial port running 5.6.5, and I've soldered SMD components of all kinds. I'm not particularly new to soldering or linux commands.

Anyway. About a week ago I saw an almost brand new PW2 on ebay with the box and the $40 amazon case. It was too good of a deal to pass up and won that bad boy for $45 (without special offers, as I later found out!).

Pictures showed it was running 5.4.4.2 but I suppose the seller must have connected it to wifi and it got 5.6.1.0.2 OTA. So in pieces it went and I started wiring up my trusty CP2104 to it. I still don't know how it happened but the TX wire (to RX on the adapter, opposite to the ground point) stuck to my sleeve (idiot mistake, I know ) and I yanked the wire along with the pad off the board. At least I know my joint was decent! It was working at first, and was giving me output in minicom as it started ( "Welcome to Kindle" - the whole shebang), but then I had to be an idiot...

Wish this wasn't a multi layer board, as I could just solder to a trace. So what do I do now? The RX and ground are fine, but are there any other attachment points for TX - maybe an SMD resistor or something like that?

Thankfully this PW2 isn't bricked, but I still want to proceed with the jailbreak, if possible.

Thanks a million for any help,
Dan

[knc1]

I do not have either the PW-2 nor the KV.

But other models (since K4) have series resistors in the Tx and Rx lines.
On the other models, almost too close to the connector pads.

Look closely, you should be able to find them, even though I think Amazon moved them back from close to the connector pads.

Hint: With a very bright light, you can see through the solder mask and first layer of board.
Sometimes it helps to take a high res. photo of the area of interest under that very bright light, and then gimp it to death to see the buried traces more clearly.

Hint: replace the pad with a tiny dab of conductive paint/ink - thin enough to run down into the via.

See my "Paint and Play" thread.

[drgonzalez94]

Thanks for the reply, knc1. I looked at it under a bright light, and I couldn't find any traces. I also played around with the pictures in photoshop but no amount of saturation or filtering would help. This is the brightest flashlight I've got (It's a big 2 D cell 25 LED w̶e̶a̶p̶o̶n̶ light). Please avert your eyes when you see the terrible soldering job. I got impatient and tackled this with a sub-par 30w iron and no microscope, instead of waiting until I got to school today. The job is less than ideal. The pad also took with it a bit of the top layer to the left of it (and exposed some copper, but there is continuity to ground, so that doesn't help) so as you can see, I can't really drop some conductive paint in there. My only choice is really to find a series TX resistor, but I'm having some trouble. I've attached some pictures if you'd like to take a crack at it.

EDIT: Tried finding it by checking for continuity with a Fluke 187 DMM but everything registers as open except components that are grounded. RX doesn't seem to lead anywhere that I found (checked all resistors in immediate area), nor does TX.

Any suggestions?

Thanks,

Dan

[knc1]

Originally Posted by drgonzalez94

Thanks for the reply, knc1. I looked at it under a bright light, and I couldn't find any traces. I also played around with the pictures in photoshop but no amount of saturation or filtering would help. This is the brightest flashlight I've got (It's a big 2 D cell 25 LED w̶e̶a̶p̶o̶n̶ light). Please avert your eyes when you see the terrible soldering job. I got impatient and tackled this with a sub-par 30w iron and no microscope, instead of waiting until I got to school today. The job is less than ideal. The pad also took with it a bit of the top layer to the left of it (and exposed some copper, but there is continuity to ground, so that doesn't help) so as you can see, I can't really drop some conductive paint in there. My only choice is really to find a series TX resistor, but I'm having some trouble. I've attached some pictures if you'd like to take a crack at it.

Thanks,

Dan

Let me see now, a PW-2 ...
Check the attachments to these posts:

https://www.mobileread.com/forums/sho...99&postcount=6

Different contrast:
https://www.mobileread.com/forums/sho...11&postcount=8

Those make it look like the traces go directly under the shield.
Amazon has been soldering those shields in-place for several models now.

Alright, if they want to be that way - what dissolves cured solder-mask?
Acetone? Maybe.
It does on my stuff, but I use a UV cure sm ink.
I haven't tried to wipe away the Amazon solder mask to expose the top traces.

And you had better wait until you get to school with access to a good re-work microscope.
They don't leave you a lot of working room there.

P.S: The on/off and reset connections on the PW-2 have been tested and found working.

P.P.S: When I wrote **bright** light, I meant it.

[drgonzalez94]

Originally Posted by knc1

Let me see now, a PW-2 ...
Check the attachments to these posts:

https://www.mobileread.com/forums/sho...99&postcount=6

Different contrast:
https://www.mobileread.com/forums/sho...11&postcount=8

So those make it look like the traces go directly under the shield.
Amazon has been soldering those shields in-place for several models now.


Alright, if they want to be that way - what dissolves cured solder-mask?
Acetone? Maybe.
It does on my stuff, but I use a UV cure sm ink.
I haven't tried to wipe away the Amazon solder mask to expose the top traces.

P.S: The on/off and reset connections on the PW-2 have been tested and found working.

P.P.S: When I wrote **bright** light, I meant it.

Indeed, that picture sure makes it look like the traces make a beeline toward the shield with less than a centimeter of space. I'm having a little bit of trouble understanding what to do as far as the reset and on/off connections. Are they to be used in lieu of the serial? I would imagine they can be programmed as inputs, but I'm not exactly sure how to do that. It's a bit above my paygrade without some kind of help or a guide. I couldn't find anything via search. Is there any detailed info anywhere, or any insight you can provide?

I'll definitely make my next attempt at this with a microscope. I tried dissolving the solder mask already but acetone simply cleans it, and no better than some denatured alcohol. I might try some medical/reagent grade stuff (if I can get my hands on it). The only thing I can think of that will dissolve solder masks on commercial PCB's are strong solvents like methlyene chloride. I don't want to do that as it can be difficult to do with pin point accuracy but I could try scratching slowly away at it now that I know exactly where the trace is...perhaps with a pick or a scraper/knife and maybe I can solder directly to the trace. Seems like a viable option, but I'd rather try the on/off reset route first, if I can find enough information to be able to do it.

I know the light is a little weak. I'll try to get some better pictures with a brighter light if I can find one but I can't promise anything

Regards,

Dan

[knc1]

Originally Posted by drgonzalez94

Indeed, that picture sure makes it look like the traces make a beeline toward the shield with less than a centimeter of space. I'm having a little bit of trouble understanding what to do as far as the reset and on/off connections. Are they to be used in lieu of the serial? I would imagine they can be programmed as inputs, but I'm not exactly sure how to do that. It's a bit above my paygrade without some kind of help or a guide. I couldn't find anything via search. Is there any detailed info anywhere, or any insight you can provide?

I'll definitely make my next attempt at this with a microscope. I tried dissolving the solder mask already but acetone simply cleans it, and no better than some denatured alcohol. I might try some medical/reagent grade stuff (if I can get my hands on it). The only thing I can think of that will dissolve solder masks on commercial PCB's are strong solvents like methlyene chloride. I don't want to do that as it can be difficult to do with pin point accuracy but I could try scratching slowly away at it now that I know exactly where the trace is...perhaps with a pick or a scraper/knife and maybe I can solder directly to the trace. Seems like a viable option, but I'd rather try the on/off reset route first, if I can find enough information to be able to do it.

I know the light is a little weak. I'll try to get some better pictures with a brighter light if I can find one but I can't promise anything

Regards,

Dan

Both the on/off and the reset are pictures of a push button switch.
Momentary contact of the lead marked 'cntrl' in the pictures to ground does just what the solder mask claims.

I.E:
Turns device on->off and off->on
The other one triggers a hardware reset.

It is the "USB boot" pair that are still a mystery.

They are 3v3 rather than 1v8 and from the picture on the sm, it looks like they are suppose to be held connected while triggering a hardware reset.

[knc1]

I tried dissolving the solder mask already but acetone simply cleans it.

Ah so ...
The doomsday prophets where wrong, there will not be only cockroaches left.
There will be cockroaches sheltering under thin films of Amazon Kindle solder mask.

= = = =

Bring out the MEK.
Just try not to melt the SoC with it.

= = = =

Seriously -
Use a hypodermic syringe with a very fine needle to put a drop just where you want to scrub (with a q-tip?).
Your sources would be an animal feed store or a human pharmacy - just ask for u-100 syringes, they come in a pack of 10 - no prescription needed.
Be quick - expect the MEK to melt the disposable syringe nearly as fast as the solder mask.

[drgonzalez94]

I figured that the on/off reset and usb boot pads were unused spots for momentary switches. I'm not sure how to conduct a jailbreak from it in the first place, however.

Anyway. I removed the solder mask with a mechanical eraser (like the kind drafters use) . It worked fine. However, the resulting point of contact is FAR too small to solder anything onto it, microscope or not.

It must be even smaller than the width of 30 guage wire. Looks like that was the contact point for the solder pad but there is absolutely no way I'm getting anything soldered onto it with any reasonable expectation of accuracy without creating a solder bridge to ground on all the exposed copper around it.

So I'm back to square one. Looks like my only solution now is to find that elusive TX series resistor.

Thanks,

Dan

[drgonzalez94]

Originally Posted by knc1

Ah so ...
The doomsday prophets where wrong, there will not be only cockroaches left.
There will be cockroaches sheltering under thin films of Amazon Kindle solder mask.

= = = =

Bring out the MEK.
Just try not to melt the SoC with it.

= = = =

Seriously -
Use a hypodermic syringe with a very fine needle to put a drop just where you want to scrub (with a q-tip?).
Your sources would be an animal feed store or a human pharmacy - just ask for u-100 syringes, they come in a pack of 10 - no prescription needed.
Be quick - expect the MEK to melt the disposable syringe nearly as fast as the solder mask.

Indeed, that solder mask is tough stuff! I decided to not take a chance with the MEK. Caffeine jitters today, I might melt more than just the SoC!

And I was afraid it wouldn't stop at the mask and attack the rest of the board. That's the least of my worries now, though.

[eschwartz]

If you're willing to wait a bit, there is a sticky thread here for a closed-Kindle jailbreak.
fw5.6.5 only (and uses a 0day so keep it in airplane mode ).

As soon as Amazon pushes a fix, it will be released.


I know, not as glamorous as a serial jailbreak but at least you have what to fall back on.

[drgonzalez94]

Originally Posted by eschwartz

If you're willing to wait a bit, there is a sticky thread here for a closed-Kindle jailbreak.
fw5.6.5 only (and uses a 0day so keep it in airplane mode ).

As soon as Amazon pushes a fix, it will be released.


I know, not as glamorous as a serial jailbreak but at least you have what to fall back on.

Definitely not as glamorous, but a sensible alternative given the predicament I find myself in with the PW2. Not in a terrible hurry, seeing as my voyage is my main device and this is merely going to be a backup device - or perhaps one I will gift to a family member.

However, I'm till open to suggestions/anyone who knows where the TX resistor might be. For now, I've reassembled the device and activated airplane mode until further notice. Thanks for making me aware of the upcoming jailbreak.

[knc1]

Now that sounds like time for a musical intermission:

[drgonzalez94]

Aaaand now I'll have that synthesizer intro melody stuck in my head days!

Perfect choice of song, knc1.