Apple Macbook Pro A1278 (K90i, 820-2936)

At first, laptop start, (briefly shorting power-on pads) but without image.
After cleaned it carefully, laptop starts, and boot perfectly, all keys works properly but power button does nothing.

It seems that power button is damaged, but when I keep pressing a key, and at the same time press the power button, this key repeats writing, (in a document text or in a terminal window) but if if I release the key, and keep pressing power button, the same character repeats in the text document until I release the power button.

I have reprogram flash chip with a new dump, but still the same.

Could be that SMC is damaged?

Any ideas?

Change keyboard.

Change keyboard?.

Yes, it is possible that is damaged, but it is not a liitle extrange that all other keys works properly?

Only power button is damaged?

Thanks.