yup usuallly power+volume down+home button usually does the trick (use the process while your phone is charging or plug to the charger), keep on trying bro if pwde pa ba na nga method... and yes mahal jud na ang Jtag because only a person with technical expertise knows how to use this.. gamay nimo sayop pud aning Jtag.. matiwasan pud na ang dead phone nimo.
Just have it check nalang sa mga cellshop nga reputable sa stores bai... I'm sure they can bring your dead phone to life at a much cheaper cost and less hassles sa imong part jud.. (if granted the above method will not work).