Trusty old MacBook won't turn on

Old faithful 17" MacBook is not turning on / powering up whatsoever. No whirring, no chime, no lights. The battery had drained completely but is now charged. I thought maybe it just needed several hours on charge because it's not been used for several months, but it is still not powering on with a full battery (green MagSafe light).

Have already tried:

- SMC reset, with and without the charger plugged in. Power button still unresponsive.

- Unplugging the battery from the motherboard for a few minutes and plugging it back in. No difference.

- PRAM reset. No response.

It had no issues last time it was used (albeit some time ago). It's been on a shelf since then.

Has it died randomly of old age? Is it salvageable?