Samsung Galaxy S2 — Bootloop to recovery issue

Hi guys.
I seriously need help right now.
My friend bought an s2 i9100 in cheep which was stuck on bootloop and he thought it could be repaired.
so we don't know what caused the problem.
But i was surprised that few repair shops weren't able to fix it.
let me explain the problem:-
when we hold power button or plug in a charger it show the logo, goes into recovery and reboots repeating it in loop.
so whenever i charge it goes into this loop.
we can use volume up & down key in those 2-3 seconds in recovery but not the power key.
we can access download mode and it doesn't reboots automatically but going into recovery mode manually also start this loop.
it's like we are only going in recovery mode again & again.
i installed this file "I9100XWLPW_I9100ODDLPC_I9100DDLPB_HOME.tar.md 5" through odin and also used the pit file "I9100_STOCK-System_2GB-Data_512MB-Preload.pit" but nothing changed.
i don't know what to do now.
i cant find any gingerbread ROM to test.
i don't know how it can be fixed,
so please help me.