[R-390] 4KC Filter

[Roger Ruszkowski]

Jim,

If you need a replacement filter, Fair Radio in Ohio had a bunch of 4KC pulls. 2KC are plum gone.

We fellows discovered some time back that the foam padding inside turns to a black tar like gunk.

A bit of ugly stuff will drift around and glum onto the wafer core stack that makes up the filter.
It is literally a mechanical device inside the can. this will pad the filter stack and cause a loss.
Half power is about expected. The filter band width is also not likely 4KC any more.

The filter can, can be de soldered, opened, cleaned, repaired, coils rewound if needed, new foam instaled and then the can re soldered.

Another used item is not likely to look any better inside.

Also consider a cold solder joint in the circuit before you just pull the filter.

Roger AI4NI




I'm in the process of aligning my 67 EAC R-390A.
All is working well except for the 4KC filter, the signal level is about 
alf (3db.)  the level of all the other filters.
The trimmers peak normally.
Bad Filter?  I hope not, any other ideas?
Thanks
Jim