[AMRadio] National 2-40 D Question

[JAMES HANLON]

Brian,
 
My first piece of advice about removing the sliding coil assembly from your NC 2-40D is, DON'T DO IT!!!  Bill Orr, W6SAI, described his process of updating a NC 2-40 that he brought back from his local radio store, and snuck into the basement after dark so that his wife wouldn't see it as I recall, in CQ magazine, November 1957.  In case you are interested, Bill replaced the RF amplifier tube with a 6SG7, the mixer with a 6SB7-Y, and he added a VR-150 to regulate the B+ for the local oscillator and the bfo.  He did suggest cleaning the finger contacts to the coil catacombs, but he warned, "DON'T try and remve the coil catacomb to make the cleaning job easier.  The author (Bill) tried it, and spent four or five hours getting it back in the receiver.  It's a nasty job - sort of like putting catsup back in the bottle."
 
If you absolutely must remove the catacomb, I can attest that it can be done.  I've successfully accomplished it on two receivers, an NC-200 and an NC-101X.  The NC-200 had a broken contact finger which I repaired a long time ago by soldering the cracked finger back together and backing the cracked area with a small piece of sheet brass, also soldered on.  That repair has lasted since about 1967.  The NC-101X had some bent contact fingers due to some wires getting snagged in them.  The fingers were not fractured, so I was able to bend them back into their original shape.  That was in 2005, and the 101X is still working OK.
 
I described my process for removing the catacomb in an article, "Restoring an NC-101X," that appeared in Electric Radio magazine #192, May 2005.  There is also some good advice in an article by Bill Fizette in the AWA Old Timer's Bulletin for May, 1988, "Restoring the National Company Sliding-Coil Receivers."  I can scan both of these articles and send them to you if you don't have copies of the magazines.  I can probably find that CQ article by Bill Orr too if I look around a bit.  
 
But the best thing to do to those contacts would probably be to work on them from the side with a good contact cleaner, for example De-Oxit, on a "pipe cleaner."
 
Good luck.  Let us know how things work out.  The NC 2-40D is a nice receiver and well worth your efforts.
 
Jim Hanlon, W8KGI