Will not power up

Trying to breathe life back into an 2008 15” MacBook Pro so my 5-year-old grandson can pound on something other than his mom’s computer. The last battery expanded to the point that the trackpad would not function. It continued to function on the power adapter alone but developed intermittent shutdowns and finally quit. I installed a new battery and used a new 85w MagSafe adapter. The battery charged fully in the computer as confirmed by the battery gauge. The computer won’t start. Here’s what I’ve done as far as troubleshooting:

Reset SMC multiple times per Apple instructions for this model.

Swapped RAM.

Disconnected keyboard cable and attempted start by bridging the power pads. No response. No fans. No screen. No chime.

Removed logic board, inspected for physical damage and found none.

Saw article about problems with C7771 tantalum capacitor. Metered and got a voltage of 6.7v.

Reassembled and repeated SMC resets.

At this point I’m thinking I either have a very nice doorstop or possibly a source of spare parts for someone else. Thoughts? Ideas? Suggestions?