[R-390] Filtersq

[Bob Camp]

Hi

There's not much to see in the picture. We are either talking about a wire that attaches to 1) the coil bobbin (which is visible), or 2) the center of the end disk (which is not visible at all), or 3) the edge of the disk (which is not obvious). It's slightly possible we could be talking about the ground strap (which is not the wire in the earlier picture).

The coupling wires are resistance welded between the disks. The actuator wire was either resistance welded or silver soldered onto the center of the end disk. If it's silver solder, any change in the amount of solder will change the mass of the disk and it's resonant frequency. To a lesser extend re-weldig could have the same problem. Of course the whole description of the center wire as an actuator may be a bit off in the case of the filter you have. It is the terminology used in the article on rebuilding filters. 

How does the "broken" end of the filter compare to the "correct" end of the same filter? 

What ever the attachment method of the wire, it needs to have good acoustic properties at 455 KHz. That rules out most plastics, and many ceramics. Hard solder or welding are the obvious choices. 

Bob

On Feb 16, 2013, at 4:02 PM, "quartz55" <quartz55 at hughes.net> wrote:

> Here is a pic of the top end with the copper cylinder that holds the coil bobbins.  It looks like it's soldered to the end disk.  This too may be problematical.  Not sure if I can unsolder this thing from the disk to attach the wire, and then how to attach the wire?  MIG or TIG?
> http://i251.photobucket.com/albums/gg287/DogTi/R390A/filtercoppercyl_zpscf59576c.jpg
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