This comment board is a mess…Seriously.
Sorry for this story I’ve presented but I think it is necessary for all of you who would like to fathom what it is we do in technology. Regarding White Screens? There can only be an answer that has understanding of the question. Questions are based on interpretations and written to convey a vague understanding. I have read most of the Pot-Luck answers which probably determine their answer by lookups and generalizations. I am of age enough with experience to comprehend manufacturing cause I have done so and been there. I am sure there are those like me who can say the same. I am not out for the point system . Here is my answer. My wife’s laptop, Toshiba, Satellite, 17in, L355-S7902, purchased in 2008. It has been around and only because I take care of things. I have a 1985 Panasonic Microwave which still beats the top of the line today. My wife complained of the white screen pandemic. To answer this question, requires a thousand and 52 answers. The GPU chip and a socket array are beyond most of our comprehension. Try for example 21 billion transistors in a given chip and even more. then there are those with perhaps a few 100K. For perspectives, lets say 144 pinout or 1060 pinout with perhaps 300, 000 to 60 billion internal transistors. That is just to give you an idea of possibilities of variables your laptop and mine could conjur in possible symptoms. So a technician has to fathom possibilities based on what little or accumulated knowledge he or she has. Enough!
Getting to the “white screen”. Our laptop was brought to my attention it had a white screen. How and why unknown but had to be determined. So I approached this thing with skepticism. First sign was heat. second sign was no air exhaust. Display appearance, low contrast, colors normal, video performance normal. Ran an onboard video check, good. Audio ….good. Typematic response normal. Ran Memory test and Processor test (Intel) both very good. Here is where I made my first mistake, I overlooked the Dual Processor. Later I looked at the BIOS to ensure all was enabled accordingly. All was fine except the dual processor was only singley enabled, the other was disabled. Why and how. Processors are temperature sensitive items. The have control for their behavior. Both the GPU and CPU’s operate in relative vicinity. Therefore cooling is again the issue. So I disassembled the main body front, back, and keyboard, and display, such that I can operate the unit as well. I was awed at how much dust accumulated in the GPU/CPU region. The fan and duct was so thick I could not even see a spec of light through. The fab was caked the processors were caked. %#*@ someone neglected this poor thing. I cleaned it up thoroughly everywhere. Temperatures were benefitting. The GPU was showing signs of physical failure, It was evident of burn. A big brown spot on top, conductive cement was burned. I cleaned both and recemented them. For as old as this unit was it was looking good now. Lastly I checked and rechecked the cables and connectors. The GPU Cable was evident of heat burn. I located one on Ebay and ordered it. I installed it and rechecked one last time all remaining devices, connectors, cables, device chip pinouts. Often when heat becomes and issue cold solder can wreak havoc. Toshiba’s are good equipment. I reassembled everything clean and tight. One thing I lacked and was quite essential was freeze spray. This is serious requirement for checking thermal runaway of chips.
So down to nitty gritty. Observations! I observed the display to act erratically in the in the initial turnon. 1st white screen happened 40 seconds after turnon ( that was before cleaning) then happened multiple times erratically between 20 and 200 seconds. Observation however was erred because I failed to observe before boot. After I realized my err, I then rechecked for pre-boot errors. This was important because pre boot versus post boot are indicative of BIOS versus OS. So I eventually deduced the symptom was both BIOS and OS related. This indicated to me the it was an issue common to both. Heat. Normally I would have use my TC Thermal Couple, wasn’t necessary. I relocated to upstairs to further observation. I had an external monitor. I connected it via VGA cable symptoms were same as internal. But! the response for failure took much longer. The internal Monitor was much more requiring power and generated heat. With external monitor the heat internal was much less. I was hoping I could continue operating the laptop considering the heat reduction. I managed to illiminate all software possibilities by deducing apps, programs, devices, and functions so that I could uninstall as much as possible. I got down to bare OS. No changes. Keep in mind I did all this so I can validate everything that could affect the symptom, functions, and the likely components. The unit works fine considering however the problem needs a replacement of GPU.
So was this a benefit to resolve?, no. Considering the time and expense. In manufacturing I had an XRAY device, and debug devices. They would have been serious time savors. When anything is purchased off the manufacturing floor defects happen. Human defects, sloppiness, inept, incompetent work, systematic errors, test errors and failure, rework slop. oversight, carelessness.
What I found was that heat and engineering/manufacturing oversight was cause for this failure. based on a life cycle of 12 years. Since 1975 manufacturing made goods that lasted nearly 20 years plus. The fact that this unit lasted since 2008, 12 years and was oversighted PMCS for nearly 8 years., this was a good item to purchase.
Bottom line? You want to pay 1000 dollars of 300. If you are to repurchase items for long term or short term that is your choice. If you will top take care of these goods or not it still amounts to your money. This item I evaluated lasted 12 years. It has been worth 3 times what the market was anticipated. This unit costed us 550 dollars back then. I have been evaluating another unit at roughly the same price $700. Since I know the quality of Manufacture my purchase will again live long. However when anything purchased becomes decadent you cant afford to pay in repair more than 1/2 its cost or as some will 1/3 its cost. Perhaps some will read this most not. I hope this has meaning to those who care for their goods.