Hi.I have just bought a Harman kardon hk770 daul mono stereo amp.I paid $20.00 and i seems to work ok.Hard to complain for the price but i noticed some poping sounds coming through my speakers after playing it for awhile.When i opened it up it looked the the caps have leaked as they are stained on the bottom.I also notice one side is hotter than the other.Can anyone tell buy the pictures if they should be replaced.I am not sure if they are original but if they are...they would be at least 30 years old.It still has plenty of power.8x 4700uf(m)50v 4x2200uf(m)63v elan.Are these caps hard to find and are they expensive.Thanks Sorry for all the questions.Total Newbie