Phone won't power on after being stuck in boot cycle

Phone likely had some water damage about a year ago as the face id system stopped working. no other issues noted at that time. a week ago the phone would randomly start going into a repeated boot cycle. phone would go into recovery mode but not DFU. was able to backup and restore which temporarily fixed issue. yesterday it went into a boot cycle again so I tried flushing the board with iso alcohol and allowed it to dry. today the phone will not power on. what would be the logical steps to trouble shoot internal components? I have a multimeter and a soldering iron. thats about it. thank you!