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Author Topic: Transplant PA-10 into a E1705  (Read 5910 times)

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SavannahLion

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Transplant PA-10 into a E1705
« on: March 05, 2012, 04:00:05 am »
Thought this might prove useful to those who own Dells..... I'm not very skilled at this kind of write up so I thought I would give a try.

This is the story of my Dell E1705. Had it for about six years (as of this writing) give or take. It's a Centrino Duo 2GHz yada yada yada. You can figure the specs out from the photos. Point is, I use this laptop as my primary dev laptop. Now, why wouldn't I use a more modern PC for development? I suppose I could but seeing as how my current project centers around a 8bit CPU, that seems a little silly to throw a Quad core multi-TB beast at that, don't you think?

Besides, as any arcade cabinet maker already knows, it's difficult to get any work done when one can easily fire up a game. Now if that still didn't make sense, stop reading, this post isn't for you.

The laptop certainly has seen better days. The bezel cracked, subsequently removed and tossed aside alongside the hinge cover. The rubber feet replaced with gobs of hot glue. Don't get me started with the hassle Dell has bestowed on us with those batteries of theirs. The case also has a hairline crack from my daughter using my laptop as a step stool.



Now that you understand the patient, let's describe the donor. It's a Dell PA-10, my second one. My first met a fate between the teeth of a puppy. A failed repair prompted a purchase of a then whopping $70 replacement... I lied, it was actually $40 off of eBay. OK I lied again, I have no clue how much I paid. It was definitely more than the <$25 these things cost on Amazon now. Still, not an investment I wanted to make... again. Mr. PA-10 started suffering from power delivery problems. Turns out, a shoddy soldering job was causing a direct short and tripping the internal fuses. A quick Google search and ten minutes with a hammer screwdriver got that sucker open and a better soldering job was done. I'll skip the details on the initial surgery of PA-10, but if it helps, the case is actually glued together, no screws involved. So break that case across the seams, just watch your internals.

Now fast forward about four months and my laptop started to complain about an "unknown power supply."


OK, well this isn't the actual error message.  By the time I thought to write this, I already added the hack. However, during failure you will hear a beep and a error message describing an error message and "reduced" performance. In the BIOS, you will see 90W replaced by "Unknown Power Supply".

Unfortunately, when the laptop can't communicate with the PSU, it cripples the hardware. Dell decided to run the CPU at half speed. What the Hell? What else did Dell think to cripple? I didn't bother to figure it out, I wanted it fixed.

Begin added section as of 05 March 2012

Here is my not to scale crappy rendering cut away of the plug.
Notice that I chose white for the plastic layer. This is the color of my plug, however most images of the PA-10 plugs you find online will have black plastic whereas the PA-12 tends to have both. Not a big deal really and nothing to worry about.

If you haven't figure it out by now, when tearing apart the power supply you'lll discover that the plug and wire actually consists of three connections. The outer jacket/barrel is the ground, followed by the Vcc layer. If you haven't noted by now, the PSU is rated for 19.5 Volts @ 4.62A. The implications of adding or moving the DS2501 into the laptop should be obvious for those with automotive applications  ;D

But I digress, as you move to the core, that is the DATA wire which makes the center pin the DATA pin and, in this case is the point of failure.

The wire is very similar to coaxial cable with an extra layer. Unlike coaxial cable, however, the center lead is not a solid wire but a stranded wire that terminates to, what else? That solid wire sitting in the center of your barrel. The failure would occur in two places. Where it enters the PSU from overly aggressive "wrapping" or, in my case, somewhere near the barrel. Since the barrel is molded, fixing it out of the question.
End added section as of 05 March 2012

So another tear down on the power supply yielded no results. I can't really see myself investing $25 in another power supply that was going to encounter this issue again. What to do?

Well a post at How to Fix Computers offered interesting data on this center pin. More importantly, it identified the offending IC as a DS2501 by Maxim/Dallas Semiconducter masquerading as a TO-92 component. No ---steaming pile of meadow muffin---? Before I ever read the question on the very same thread, I thought, "could this circuit be moved into the laptop?" Of course, I had considered installing the damned DS2501 with a ATTiny and a bit of software to simulate the data but... ah that's probably another project. There is also some discussion on the internet of hacking the BIOS to not look for the DS2501 data but... well... that's a project that would takes month and would only work on specific versions.... I eventually decided to do this the hardware way.


A crappy render of the offending IC. The pinouts are as follows:
Pin 1 = Ground
Pin 2 = Data
Pin 3 = N/C

If you're going to do this, better hustle, the DS2501 datasheets are all but gone, I had to get them from secondary sources and the DS2502 datasheets (which you won't really need but yeilds useful information nonetheless) are squirreled away on Maxim's site).

Tracing the circuit reveals a 130 Ohm SMD resistor from the data pin to the center wire on the cable. Yes, it is innacurately identified as a 131 Ohm, mine measured almost exactly 129.7 Ohms. A mysterious diode(?) is identified as tying the ground to the data. Speculated as a Zener diode to prevent over voltage to the data pin. Not very useful from the descriptions so... whatever... In any case, I have no idea what it is. It looks like an orange barrel with red/black/blue* bands with the red on the data side. It doesn't matter. The three components are desoldered and resoldered onto a small piece of breadboard. A simple multi-meter is enough to discover which three components you need to remove. They're all hanging off the data pin of the cable.


The circuit on top is the original circuit of interest. It does not show the entire PSU circuit.
The circuit on the bottom is the modified circuit once the three components were removed and installed in the laptop


As you see, the circuit is quite simple. The only difference is the lack of Vcc (labeled as V0 on my power supply) because pin 3 is not connected anyways. My guess is it's just there for physical support. On my PSU, it was tied directly to Vcc though, why? An intentional misdirection on Dell's part?

The addition of the header allows me to use a non-altered power supply without having to worry about the DS2501 stomping all over each other. I did not "flatten" the components Ben Hecke style. I already damaged one of the leads (The all-important GND of all things) trying to remove it from the board and I didn't want to stress the metal further. Hell, at 12:30 AM I really abused the ---steaming pile of meadow muffin--- out of this poor IC. A quick peek at the datasheet reveals a maximum of 280C for 10s during reflow. Ooops.


Once I built the circuit on a breadboard whose picture I intentionally omitted as it should be an excercise best left up the to the reader anyways. OK, I forgot to take a picture of it. I turned my focus to tapping into the mainboard.



The power connector is the silver square in the upper left. Use your multimeter to figure out where to tap into the data and GND lines from this connector. It was a little confusing to me at first so you must use a multi-meter to figure it out. Especially as it was.... 1:00ish or so.. AM.... Getting the main board out was a ---smurfette---, took me the better part of twenty minutes to figure it out. Hint: For this model E1705, push on the audio connectors on your right until they clear the case

I originally wanted to install the new circuit just behind the jacks on the board in a cluster of holes there. However, as it was now 2:00 AM, I really didn't want to make a mistake and construct a circuit into an area of a board that had no business having said circuit there. So I opted to build the circuit into a bit of left over breadboard and hot glue it right next to the battery.




I finally reassembled my laptop, with the new circuit at 2:30AM. This was a do or die kind of thing. I have two small children and I had taken over the entire kitchen table. If I didn't complete this tonight, it would have to be reassembled and the project would have to start anew the following night. So does it work?


YES!

Begin added section as of 05 March 2012
Some closing notes:

Even though I write about the PA-10, this would apply to any of the compatible cross reference DELL power supplies including the PA-12. For our purposes, the difference between the two is minimal. The PA-10 is 19.5v @ 4.62A yielding 90W. The PA-12 is 19.5v @ 3.34A yielding 65W. If you own a docking station, you need the PA-10. I have seen mention of a 130W supply which appears to be the PA-13 which is a 6.7A beast. However, I don't know if it is compatible with my E1705

Interestingly, Dell refers to PA-10/PA-12/PA-13 as "families" and not as models. Referencing strictly the model numbers yields dozens of model numbers. I've not bothered to list them here since there isn't a clear correlation between model number and "family" and I have no way to verify any of it. Why Dell opted to add this kind of confusion is beyond me.  ???

The PA-10/PA-12 family appear to be fitted to:
Dell Inspiron 1150 1420 1501 1520 1521 1525 1526 1720 1721 300M 500M 505M 510M 6000 600M 630M 640M 700M 710M 6000 6400 8500 8600 9200 9300 9400 E1405 E1505 E1705
Dell Latitude 100L 131L D400 D410 D420 D430 D500 D505 D510 D520 D530 D531 D600 D610 D620 D630 D631 D631 D810 D820 D830 E4200 E4300 E5400 E5500
D-Series Docking Stations X1 X300
Dell Precision M20 M60 M65 M70 M170 M1210 Dell Studio 14z 15 1535 1536 1537 1555 1735 1737 XPS 13 16 M1530 M 1530 Vostro 1400 1500 1510 1520 1710

The PA-13 appear to be fitted for:
Inspiron 5150, 5160, 9300
Latitude E5420 E5520
XPS M1210, M170, M1710, GEN 2,
Precision M90, M6300

Take the above references with a grain of salt, this was a list grabbed during a quick Google. Don't blame me if you don't do your research. I found pages that added at least twenty more to this list.

On an interesting note, it's been reported that the laptop is what supplies the power on the data pin. This is further confirmed by the layout of the PSU as it relates to the circuit (see above circuit diagram). The voltage is super low, purportedly around 2.5v or less. Just barely enough juice to drive a microcontroller if one wishes to create a simulated DS2501.  >:D

End added section as of 05 March 2012

*I am somewhat color blind and this was seen to me as being blue. However, after desoldering this SMD component and examining it for directionality under a jewelers scope it looks to me more as a gray or green. :( So use a Multi-meter to determine directionality before removing it from the circuit or just note which side the red is on.
« Last Edit: March 06, 2012, 12:42:23 am by SavannahLion »

SavannahLion

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Re: Transplant PA-10 into a E1705
« Reply #1 on: March 05, 2012, 04:10:17 am »
So there's my crappy write up.
« Last Edit: March 05, 2012, 11:58:35 pm by SavannahLion »

DillonFoulds

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Re: Transplant PA-10 into a E1705
« Reply #2 on: March 05, 2012, 10:58:42 am »
Thanks! to be more specific is this for the thin barrel with center pin type plug that Dell uses? I multimeter'ed mine over the weekend and happened to notice it seemed like the power was coming from the inside of the ring, rather than the pin like i originally thought. This would explain what that pin is all about then...

SavannahLion

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Re: Transplant PA-10 into a E1705
« Reply #3 on: March 06, 2012, 12:39:17 am »
I added a crappy rendering and updated the write up accordingly. Let me know if it helps.

DillonFoulds

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Re: Transplant PA-10 into a E1705
« Reply #4 on: March 06, 2012, 01:02:40 pm »
Yeah, that's exactly what I was referring to. What a crap connector. The only nice thing about it, is that mine is so worn out, I don't have to worry about the laptop breaking when the kid pulls on it, since the plug just falls right out.

It's loose, but not so loose that it falls out on it's own... just yet...