[R-390] Ded Filters

[ToddRoberts2001@aol.com]

In a message dated 11/26/2002 10:09:53 AM Eastern Standard Time, 
wb3akd@arrl.net writes:


> I need a new project like I need a hole in the head but are there any dead
> mechanical filters out there?  I'd like to see if I can open them and see
> what the failure mode is.
> 
> 73
> 
> Tom
> 
> WB3AKD
> 

Hi Tom, sounds like a good project. From what I have learned and read over 
the years, I believe the number one failure mode of Collins mechanical 
filters is CORROSION. The filters are supposed to be hermetically sealed, but 
from what I have seen myself and in other pictures, the filters are notorious 
for having corrosion inside. What ususally happens is corrosion eats away the 
fine wires from the transducer coils usually at the solder joint to the 
feedthru connector. When the filters are opened up what was once some kind of 
foam rubber cushioning inside has "dissolved" and there is likely to be 
greenish corrosion all over the metal parts inside. I believe 99% of all 
troubles inside are failure of the transducer coil due to corrosion, and 
sometimes due to electrical faults (short-circuit of B+ to ground thru the 
filter). 73 Todd Roberts WD4NGG.


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