Transistor issue in Concert Lead?

[xsolarusx]

So, I recently picked up an early 70's Concert Lead for a few bucks.  The amp powers up and everything seems great, except for what almost sounds like ring modulation(it's noisy and hasn't completely affected the signal, but it's definitely there).

I was told it may be a transistor issue, but maybe someone else can shed some light on this? Any help is appreciated!

[xsolarusx]

bummmmmmmmmmmmmmmmmp

[mckinnon audio]

   Hi there,if I remember right,a lot of the trans. in the preamp are in sockets,they're not soldered in.Could be dirty / corroded sockets and trans. leads.You have to take them out to properly clean them,so make sure they go back in the exact same way / polarity or you're in big trouble !! I usually take the socket right off the board and solder the trans. right to the pc board.Hope this is of some help,good luck,Mel.