I've just had a 1526 come to me for repair. Sometimes it would start properly, and other times it would turn but no display or life.
Many would assume this to be a reflow//reball/chip fault, but hows about this for silly.....
I did the usual, of applying slight pressure to each corner of the board, and that made it always boot if done the right way - indicating at first, a reflow problem.....
Next, i took the lower panel/memory cover off, and found that slight pressure to the CPU heatsink made it boot perfectly.
Turned out on this one, it just needed the CPU reseating properly :-D
Maybe this could happen on others of the same model ? I can't say as this is the first time i've worked on this specific model. I've only seen bad CPU fittings before on Packard Bell R1000 series'.