A1286 won't turn on - black screen

A1286 won't turn on - black screen, have reset SMC, power light on

MacBook Pro A1286. Removable battery and hard drive.

• Battery charges fine. LED indicators show charge level. Power adaptor shows orange when charging, green when charged.
• When turning on, power LED lights up, the chime can be heard, but nothing on the screen (no flashes, etc.). Keyboard backlight does not light up; caps lock key does not light up when pressed.

What I've tried:

• Have reset SMC with and without taking the battery out first; charging cable responds with green light
• Have tried holding Command-Option-P-R startup as suggested in another thread

Have plugged a HDMI cable in to a TV, but nothing shows

Can anyone have some solutions thanks.