Friday, June 25, 2010

Writers Block? Nahhh

Due to activity and being summer I had held off posting some items that had come across my desk.  So shortly expect a flurry of activity.

A recent email asked several questions that I think I can answer before hitting the grind again.

Do I do my own reballing?
No, the method I use corrects the solder balls.

The biggest defect of BGA and RoHS solder is tempetature and contraction of metal. Down on the atomic level, the valance bonds of the multiple elements used (in solder) break and you get a weak composition. Excessive heat causes metal to retract to themselves. So instead of getting a bond, you get contact.  Example: In the DV series, the breakdown is as follows.  After a period of time and use, the vents on the heatsink will become blocked.  This is from typical use and the placement of the Air In slots on bottom. They draw in fibers from pants, shirts, sheets, bedding, pet and human dander and carpet. Often larger than the vents exit. As more and more collects the vents become blocked.  So the fan runs longer (also collecting more lint faster). this in turn causes the CPU Heatsink compound to breakdown and dry out making it brittle and hard, and unable to do it's job. When the CPU overheats- it shuts off. May loop and repeat. All during this time, the GPU is overheating too, and the solderballs are expanding and contracting.  If there was a poor contact that was simply smashed down to make an electrical connection (and held down by heatsink screws). A 3-12 micron gap can occur on a non-whetted pad. Note: human hair is about 40microns.

Where do I get my schematics and chip info:
Additional costs and searching for schematics is a waste of time for me. I guess you can say I am 'old school'. Schematics can help, but between the Chinese manufacturers and the US branded companies. They try to lock up the information and it is not readily available in most cases. (I will point out sometime that many designs are meant for failure and not intended to be repaired) This I have proof. So you wind up spending 2 hours looking for a schematic. And then the manufacturer change suppliers, the suppliers change part numbers.
Example: in the DV6K/9K the mosfet switch for the charge/power went from AO4407 [Alpha and Omega] which was a hard company to locate, then switched to an AO4430, then to ME49xx or something of that nature. All this before many US part stores got the first version.

So what I do is read the specs for the individual part and get an Fairchild substitute list. Like the FDS6679 [Fairchild]is substituted for the AO4413. My favorite suppliers are Digikey, and Newark Electronics. As well as direct from the manufacturer such as MAX8734 [Maxim]

Liquid Spills
Are typically done in a 3 chemical bath. The first bath (after removing CPU and many of the stickers as possible) is done with boiling hot water [pure bottled] No Dasani or any water with mineralsBelieve it or not Aquafina works for me- This loosens and cleans most sugar based spills such as Wine, Cola, Tea and Milk. And let it soak until the water cools. Then depending on how great the spill, I will soak it in isopropyl alcohol completely covering the board. Then rinse again with boiling water, and alcohol again. Then allow to sun dry- we have plenty of sun here in Carolina.  Less sunny climates can put in Oven at 225F for about 20 min. [NOTICE that is Fahrenheit not Celsius] No higher! It is a motherboard, not a frozen pizza. Alcohol in Ultrasonic tanks works, but everyone does not have access to them, or the money. And they still should be rinsed with pure water. You can use compress air and blow much of the water out and speed up the drying time.

How do I monitor temps:
After a number of years you tend to learn tempetures by the chemicals used. like water boils at 212F.  Smoke and oxidation points of fluxes are somewhat ingrained in me from memory and 20+ years using them, when it smokes, it has reached the oxidation point.  You can use/get an IR temp probe if needed.

How to measure voltages, supplied to motherboards.
You test at the DC IN and to the largest NEG mass. Not to a heatsink frame or anything connected to the motherboard. The NEG may be isolated.

How Do I Replace LCD backlight tube.
I've stopped doing that now, the prices have fallen on most of the common screens 14.1 and the 15.4 so there are plenty around at low enough price rather than waste an hour replacing, when I could do two DC jacks. And most of the new 15.6" use LED so that problem is no longer.

Managing Screws.
This used to be a headache. Knowing and remembering which screw came from where. With the greater number being on the bottom cover.  So what I have done, is to use Scotch brand invisible tape over the holes. Same for most of the other locations that can keep the screws in place.  Beats having to guess which one is 2.5 and 3.0 then using the wrong length and causing a bubble on the wristpad or other visible place. OR even puncturing the plastic.  Another thing while on the subject.

You should not be using a cordless drill as a screwdriver. It over torques the screws, damage the brass retainers in plastic columns, or breaks the screw holder. You can get cordless screwdrivers for less than $10. Which will prevent further damage later. And have a set of mini-drivers (magnetic if possible).

Testing Caps
Sure caps can and should be tested, especially the brown ceramic caps. Most of the electrolytic caps give you a visible hint if bad. But do test them too.  You can use a Tweezer RLC meter for most of the tight places. Measures resistance, uHenry, and uFarad values. They run about 20-40 on eBay and the autoswitching are faster and better. So don't be too cheap and spend more time switching settings.

Do I read any other sources/blogs
No, that was my biggest headache and reason I started on this project, nobody that has experience and deep details on their findings are reporting much.  The techs are simply not journaling/chronicling their findings.

Trying to find a specific answer in a Forum is a nightmare. You ask a simple question and you get 25 people that want to tell you about their puppy, mother's flower garden and you never a direct answer. Then others tend to throw in questions totally unrelated. You're asking about HP and they say they have the same problem in a Gateway.  The moderators are not moderating, and thus the whole technical field has become as 'Babelized' as the Chinese parts industry.

Do I use diagnostic software
If is a particular dog I will use Belarc. But most of the time I only deal with electrical/electronic issues.  When it is working right Windows will tell you if there are problems. 
No USB but all the drivers are loaded and a Keydrive will not light up or access- I check the ports (visable inspection), USB controller chip or the data driver chip.
No audio - check the plug, and the audio controller chips.
etc...

Hope that's enough for now, will unload camera soon, so you can see some of the dogs! that I had to work on.

5 comments:

  1. I really like you and your blog. Keep up the good work. I'm thinking of taking up electronics because of your blog.

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  2. Thats thorough except for the process you use for reflowing GPU's. There is SO much mis-information on the subject it would be nice to hear from someone with experience what your method is.

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  3. Thanks for the very prompt, detailed and helpful answers, Kevin.

    Larry Sabo
    Sabo Computer Repairs

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  4. MattBrad32: As mentioned earlier, I am wanting to 'perfect' as best as possible. I would hate to post a solution with 99 revisions. It's coming and when it does it will be complete and thorough. Still it is not intended for the layman, but most techs and shops will be able to use it with confidence and a high level of success.

    Larry/Brad: thanks for posting comments, sometime I had felt I was typing to myself. But do appreciate the feedback. And I even reread what I post so that clarifications are for even non-Americans that might be reading. Sticking to middle English as best as I can.

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  5. Definitely keep up the good work! Sites like this are extremely rare to find. It's nice to see someone else going through a lot of the same problems I see and use similar solutions. I've been doing this 20 years but could still learn a lot. Thanks again.

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I cannot repair laptops for you via the internet, I can only answer questions related to posts. This is because I have not had experience on every motherboard that is out there. Bear with me.

If you do need it repaired. Contact me for quote (US/CDN Only)

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