System Changer - Poor Sound?

[First Spear]

I fired up my System Changer after it sat in storage for years. Each Atari 2600 game I play has some kind of problem with audio. I don't remember it this way, but the hardware is so old Im not sure what to blame... The TV is LCD with a coax input from the Intellivision. Inty games sound fine, Atari games look fine but low-pitch sound has "pops" so loud that they mask other sounds.

 

All ideas appreciated on how to fix.

 

Thanks.