If it turns out that the logicboard is dead. Then try to "disarm" the covering metal shields on the motherboard.
Then try to put the motherboard only, without the shields into isopropyl alcohol. The alcohol is very high concentrated, and will dissolve the the oxidation on the motherboard. Let it lay in the alcohol for about one minute.
Afterwards try to gently brush with a toothbrush on the chips, wash it in the alcohol and then dry it for 24 hours.
This fix should only be done, if the motherboard is already dead. So try to troubleshoot the device before this fix.
// Fini