sell your v4 on ebay !!! then invest on a v5 onwards pref a v7 then get yourself a mi or crystal chip ..... I think others here will advise you to sell on , at least you will have a decent ps2 to play with for the sake of a few £££££££ or $$$$$$$ ,, i picked up a v7 on ebay for £35 and its been spot on since !!

keep eye open and you will get a good deal