What I Learned From Fixing my Laptop's Motherboard
spinellis.gr
spinellis.gr
You know that awful sinking feeling you feel when you've just done something monumentally stupid and embarrassing that you're going to have to fess up to? It feels twice as good +5 when you rescue yourself from it with your geek super-powers.
You can replace the circuit board on a WD drive with a match from the exact same model, from the same factory, manufactured the same day (guessing by the serial number anyway), and the drive will still fail to give you your data back.
When the system area becomes unreadable or doesn't match the contents of the eprom on the controller board, WD drives will show up in BIOS with a generic model name and no other information about the drive. There's no easy way to coax them into cooperating.
If you're lucky, you have one of the WD models with an accessible eprom on the controller board, and you might be able to either desolder and swap it with the replacement board, or, if you have the appropriate equipment, use a special clothespin-like tool to latch on to the chip's pins, read its data out, and write that to the donor board. If you're unlucky, the eprom is integrated into another chip, and nothing short of some pretty expensive equipment will be able to handle it.
However, at this point, almost everyone that doesn't work at a professional data recovery lab is waaaay over their heads, and only making the recovery job harder (or impossible) for the lab.
Additionally, a lot of WD drives now have the head stack spindle mounted by a screw to the top cover; once you pull the top cover, you've lost the head calibration for the drive. Getting any data off the platters at all at that point requires a moderately expensive homebrew tool with several calipers that screws into the head stack spindle; you manually adjust calibration until data starts coming in reliably.
We no longer do physical data recoveries in our shop; about the end of last year these piece-of-crap drives started coming in, and none of the old tricks worked on them. We looked into the equipment (and subsequent training) required to do these sorts of recoveries, with an eye towards providing very-low-cost recoveries (since we have plenty of other revenue streams), and we simply can't afford the initial $15,000 outlay for it.
We've made it our mission this year to get effective data backups working for every single one of our clients.
TL;DR: swapping controller boards and other tricks no longer work. You really really really need to have backups.
As I was plugging in the molex, Zap! Big blue spark, and the computer was never to boot again.
Embarrassingly, I fixed it with a solder, luck, and a replacement pin made from a paperclip.
Necessity is the mother of invention. And functional TiVos.
Reading stuff like this always makes me feel like a second-rate geek! I've had my fair share of soldering iron burns (for my senior project in college, I cracked open an RC car's remote and connected it to a BASIC stamp, which I controlled via RS-232 and a network socket), but the parts of this article which the author considers "easy" stuff are still a mystery to me. For example, "According to the application note I could use a simple signal diode, so I just pulled a 1N4148 diode out of my component drawer." A simple what diode? A 1N4-what diode? My component drawer? I don't even have a... help! S.O.S.! Man overboard!
I'm sure that I could come to feel more comfortable with stuff like this if I went out of my way to learn more about it, but the applicable extent of my electronics hacking day-to-day has been unplugging the rumble packs from my Xbox360 controller. Most of the things I use on a day-to-day basis are not devices that I feel comfortable screwing around with!
So true.
I was poking around inside a small headphone amplifier to see what was causing a crackling noise (I assumed a loose wire some place) when I tugged a bit too hard and popped off some otherwise healthy wires. I was crushed.
Then I realized I have a soldering iron. I did a crap job (I too am way more CS than EE) but I reattached the wires and got it working again.
Later I learned that the crackling was coming from the cable being plugged into the amp, which was basically fine.
http://aeminium.org/slug/hardware/gainclone/
Related to this article, I also fixed a TFT monitor I got from the trash, by following a similar approach, although without any schematics :)
http://aeminium.org/slug/hardware/lcdfix/
There was another time when I fixed a big old CRT TV by just replacing a shorted capacitor (€1 part) on the high voltage transformer circuit.
The brand representative at the store where my parents took the TV said that it would be too costly to repair and to throw it into the trash, so they kept the TV until I went there for holidays break.
Last year a friend had her laptop showing just half of the screen image. I opened it, saw that it was a flat wire connection problem and installed ubuntu, replacing XP in the process. She would need to buy a new laptop, so instead she used the money "saved" and bought herself a nice digital camera.
And this goes on an on...My point is that some things are easier to fix than others and if you enjoy electronics and tinkering, it's a fun way of spending time, learn new things and to keep (working) stuff away from the dumpster.
Anyways, I had experience soldering SMDs before so I wasn't too worried about the repair, but there were too many power mosfets and diodes and and a ton of devices at the same potential. Testing voltages and continuity with my multimeter was mostly futile (and I used datasheets the entire time). I'm glad you found the problem.
I bought a Teac 4-track open-reel tape recorder many years ago. Still have it, as well as the docs. I swear you could build one from scratch with the info provided.
The option to open stuff up (phones, radios, TVs, tape players, etc.) and make them do things it was not intended for was magical. Maybe Arduinos allow for something like that feeling now; seems infeasible for most general consumer electronics nowadays.
Then I worked out a simple serial bit twiddling scheme to exchange bytes a bit at a time and coded it up in C as a kind of software serial port. On the PC side I ended up with something that looked just like a simple terminal that happened to talk out the printer port. On the Mephisto side, I replaced the 64K byte EPROM with a 128K byte EPROM. I changed the cold boot vector to point at "my" 64K, which first checked to see if the printer port was hooked up. If it was hooked up, then the CPU stayed in "my" area and ran a monitor I had coded up for the occasion. If it wasn't hooked up it vectored back to the original boot code and the chess computer worked as well as it ever did. I layered a loader on top of everything and had the incredible satisfaction of running standard C sieve of Erasthonese (sp?) on my new 68K computer, (complete with 16K RAM).
Ah good times. Pretty hard to do stuff like this today when everything gets packaged into mega chips, not to mention the tiny scale of everything these days.
http://www.djtechtools.com/forum/showthread.php?t=28014
Source code: https://github.com/dublindan/Midifighter
People who share their work make the internet (and the world) great.
Always remember your maker rules: http://wondermark.com/tink8/
We plan on releasing some proper video demonstrations of it in action and to write a few blog posts about how we did it and our experiences when we find some time.
One of the things I really took with me from his instruction is a disgust at the "Death of the TV repairman". People would rather throw something in the garbage instead of having it fixed...not that it is always their fault. It has become cheaper to purchase an item than to have it fixed, that combined with the fact that most manufacturers typically do not release schematics until the item is out of production (if they do at all) and an increased effort by manufacturers to not allow anyone other than their techs to work on things (i.e. special Iphone screws, warranty voiding tape, part numbers removed from chips).
Remember, just because it is small and complex does not mean it cannot be fixed. If it was built it can be rebuilt (or unbuilt, see ifixit).
Just because a device is "dense" or heavily populated does not mean it cannot be repaired if done properly, if the schematic is provided (and accurate per revision) and you can still source the part it can be repaired. Even IC's can be removed it just takes different tools (i.e. solder pot, hot air pen, hot plate, etc).
I assure you there is no difference between troubleshooting old tech and newer stuff its just different. An IC is just that an "integrated circuit", meaning they just took what used to be an entire daughter board and made it on a silicon chip. I would actually argue that it could be easier in some cases to find an issue on newer stuff since if a chip is failed you just replace it (if you can get it, which is the real problem).
It's just like he said in the article use the datasheets if you don't have a schematic typically they are just using some circuit that someone designed 20 years ago and put in the datasheet as an example.
I understand the labor cost involved in fixing an item but I would argue the long term cost of replacement/improper disposal (even recycling...have you seen the little kids with the campfires of circuit boards in india/africa that are trying to reclaim the valuable metals...that is the cost I am talking about).
As an electronics tech I can tell you that I have worked on many complex circuits in the field and in production and I have never had a problem with the complexity...but I have had many issues with finding "one off" IC's and schematics.
Things are not always about money...sometimes its best to fix things just to fix them (and hopefully learn something at the same time).
Also, consumer electronics are built to fail. If they were not the manufacturers would require some IPC class, nobody wants quality though...they want cheap.
Exactly.
We have a fantastic old (probably 10+ years) clothes washing machine. The lid switch went dead about 2 months ago. We looked at (possible) replacements at a retail store and realized that there was absolutely _no way_ to repair many of the newer models -- a process you can count on given the MTBF of many electronics components. A $10 replacement lid switch from Ebay and a 15-minute solder job and the old machine was back to working beautifully.
It's sad... despite having a professional electronics lab in my home (including hot-air rework, stereo microscope, and a great oscope), I doubt I could repair many (most?) modern electronics failures.
BTW, I am jealous of the stereo microscope and hot air rework station...those are on my list for my shop (Just got a Rigol oscope to hack a few months back)...Sometimes, I miss working in production and having access to all that..although I have better handtools now.
Double-sided tape, or actual compartments, sound like a much better idea.
Another strategy is to screw them back in, lightly, into the same holes they came out of (after removing the thing they were holding down of course). Not practical with a lot of gear though.
I stick the screw heads to the tape. They stay pretty well, are easy to get-to, and it's easy to arrange them as you want. I usually put them in a compacted form of the layout they were on the board.
That model in particular had many screws that shared the same pitch, but with different lengths. The thought of piercing something with a 10mm screw in a hole meant for a 6mm screw was scary. I thought this technique worked well.
I always want to do photos but I am usually too dirty and/or lazy.
I was really confused that the world's biggest electronics concern wasn't able to replace an EEPROM. Luckily I came across bios-fix.de and paid 65 Euros including shipping to get the old eeprom soldered out, flashed and soldered back in.
I wish bigger companies would actually try rather than going down the service path of least resistence :(
If you are like me you also salvage as many parts from what cannot be (or is not worth) fixing there is always something else to use the parts on.
Modular components and hardware standards with many third party manufactures. Laptops will always hold second computer status for me.
Replacing through-hole parts on motherboards is exceptionally difficult. There's so much copper in a modern multilayer board that it's very difficult to get enough heat in without cooking something delicate. Even with preheat, a reflow gun and a powerful iron it can be very hard going.
Replacing broken PSU connectors is one of the most common laptop repairs and should be an easy job, but has a dismally low success rate.
I agree though - a bit of knowledge can be a powerful thing; a 'resistor pack' for my car (to regulate the 4 speed aircon blower) is 80UKP + labour to replace when it fails but the most common fault is that the thermal fuse (approx 0.80UKP to replace) blows when the airflow is reduced by an air filter that just needs a clean-out.
I was in the process of replacing the failed fan on the CPU heatsink. (Had to transplant the fan from a smaller heatsink that came from a lesser t42 with a smaller heatsink that didn't fit... Long story.) Prior to the procedure, I wanted to carefully see if there was even voltage on the FAN pins. I wasn't careful enough and thought I shorted the pins. Indeed, when I connected the working fan, it didn't work. So I figured that a fuse blew somewhere. Did some searching on the web, found a partial schematic for the board, found the 1mm x 2mm FAN_FUSE (or something) and soldered a wire on top of it. To my surprise it worked. Still using that t42 when on the go.
This t42 is my Oliver, basically.
Well, I couldn't find the service guide, all the ones I found were diagrams, but not a guide on how to dismantle the laptoo, so I decided to figure it out myself. After 4 hours I managed to take the whole motherboard apart and extract all components, then another hour to install the new one. It was pretty challenging, but I managed to close the case with all parts in place and no extra screws lying around.
The best thing that I learned these days was photograph every part of the disassemble process, and where you put each screws and cables, with this you can go back in the time and see how to reassemble much more easily
How else was he to access his private key?
Well, the diode did as it was supposed to, and prevented the reverse-polarity from damaging anything of vital importance.
Nice write-up.
I don't think so. If the diode were being used to prevent reversed polarity, it would simply have not conducted. If it were a normally-reverse-biased shunt across the power supply, then blowing it would have left the laptop unprotected but otherwise functioning (and it would have had to blow something else in the process, like a fuse). So I suspect it was intended for something else.
For more formal stuff, see electronics/digital computer fundamentals/etc. courses at your local community college or university, or see if your local Maker community (if there is one where you live) can point you at more targeted local resources.
Probably start with older electronics from the late 80s, early 90s. Buy stuff from Goodwill or thrift stores.
Stay away from tube TVs (high-voltage - danger).