Good I have a Acer Aspire 4520 these machines come with a chipset with an nvidia video card heats it more than you can discipar heat and in a year or two more will not start desueldan contacts by heat.

Is repaired with an industrial dryer is 30 seconds chip points to squeeze it with a screwdriver and ready works! then you put a laptop coolers and more breaks!

I did all that and until one day I forgot the USB cable disconnected from the coolers and returned to break

I return to do the same? no other better solution? or throw them away?

for good working your acer 4520 you must replace chip - nVidia MCP67MV-A2 (~70$ chip + reflow work).
but I recommend replace motherboard from acer aspire 4320 model (this is the same as acer 4520 motherboard, but with Intel chipset) (=$40 on ebay, like #130595084575 lot), heatsink (+$15-20 on ebay) and Intel CPU (from +$5 for celeron M5xx to $xx for dualcore-core2duo cpu's)

reflow with industrial dryer without replace nVidia chip has a temporary working effect (from few minutes to few weeks) and not good, and not long time working.

p.s.
sorry for my bad english ;-)