[R-390] Filter repair

[quartz55]

I took apart another 4K filter someone sent me today, mostly for practice.  I used that big Ungar iron and just put the thing against the disk on the end with a bit of solder, let it heat up and just pulled the disk off like nothing.  The bottom end was a bit sticky because of the ground strap that comes from the disks, but it was much better than heating up the thing with a flame.  I've got the thing cleaned up, I could hear the filter assembly shaking around inside the can when I got it, so of course the ground strap was broken off at the filter.  One of the coils visually looks good, I haven't checked the resistance, and the other one has broken wires near the coil, I'm still hoping I don't have to rewind it, just add wires to the ones that are broken.

I'm thinking I could repair these things in about 2-3 hours if there is no big issues inside.  It took me about 45 min. to remove everything and clean it up, including taking out the coils and cleaning them up.  I haven't messed with the tape on the outside nor the bias magnets since they seem stable.  All I did was clean the goop out and make sure none was in the copper disks.  Hopefully this thing will go back together easily (I'm worried about soldering on the ground strap) and work satisfactorily.  The Ungar didn't bother the label on the filter at all, so that's nice.

If there were a source of foam PE that would easily be worked for the inside, these things would be easy to repair.  I'm thinking about getting one of those surgeons loupes that focus out at arms length instead of the close up headband.

Dave