[R-390] 60 Hz Hum Output from R-390A IF Module

[Flowertime01 at wmconnect.com]

Jon Schlegel,

Are you having any luck with your hum in the If deck?

I am first going to suggest you drop the extender cable and get the IF deck 
back into the receiver. Back when, any test that was not all things in 
place was just a distraction. When being defined as 1968 to 1975. If you have to 
work on the IF deck live (yes you some times must do this) then set the 
receiver up on end and swing the IF deck out on the bench. Stick the knobs back 
on the IF deck shafts so you can twist the bandwidth and BFO. Get off the 
chair or get the receiver on the right height of bench that lets you look 
into the deck where you need to work.

If this still gets you 60 cycle hum (it may) then start swapping tube out. 
Always tubes were the first line problem. Second is clean the tube pins and 
shields. Third is all the ground points need to get unbolted and rebolted to 
get the crud out of them. Do not remove the bolt. Just loosen, deoxit bath, 
and retighten. Fourth is a leaky cap. One of the bypass caps have gone 
resistive and not doing a good filter job. 

These are not easy to resolve. The deck forms a big loop and finding source 
point is not an easy task.

Let us know how the project is going.

Roger Ruszkowski