Heathkit SB 614 Station Monitor Video #1 - Checkout and Testing 

25:42 That is definitely a cool setup with the pot and rotary switch. Thanks for sharing, Jim. 73

The vertical input is there so you can ALSO use it as a O scope. You will need more power to get more then a 1/4 inch deflection on the CRT. I rebuilt mine that got hit by lighting and blew most transistors. It looks to be working as it should.

I wonder if that's fungus or some kind of biological growth