I wasn't planning on buying another National, but I found this at a thrift shop looking pretty forelorn and priced at $10. I figured I could part it out or use it as a trade down the road.
Damned if it didn't work almost immediately (see baseline below), so I don't have the heart to tear it up. Instead, I thought I'd use it as another repair/restoration guinea pig.
I'm becoming quite a fan of National products.
Background: this ran from 1947 to 1950, according to The Radio Shoppe. The earliest National advertisment I've seen is in the November 1948 issue of QST, though I did see a dealer's ad from earlier in the year (left). This is the little brother to the big NC-173/183 machines, at least in styling. It has far fewer bells and whistles than my NC-173, but it does include a built-in speaker.
There are also an NC-57B and NC-57M variant. I haven't yet determined what the differences are.
In case you care, I found the following to be useful or interesting:
- BAMA, the Boat Anchor Manual Archive - original operator's manual, schematics (free)
- Antique Radio Forum - a thread on the subject
- CQ CQ CQ DE W0VLZ - an NC-57 restoration project
- Marty's Web QTH - KJ4LQX - an NC-57 restoration project
- Radio Bay - a nice webpage on this unit (and more)
- Radio Boatanchor Parts - piece parts from a parted-out radio (among other things)
- The Radio Shoppe - nice photos
- YouTube - Nice video, but his is in a bit better shape to start off with (cosmetically anyway)
I'm not going to do the whole song-and-dance that I did for the NC-173, but I'll do some. I found this at a local thrift shop where it was piled in with the clock radios and curling irons and such. $10. On the surface it's obvious why: this one has been through the wars. The great thing about a sheet-metal cabinet is that they can take the use and abuse that would destroy a wood or plastic cabinet; the bad part is that they look like hell after doing it.
Known missing: the bottom metal panel, all the knobs, and the dial light. Known damaged: the plastic dial protector, the speaker, and the bandspread dial cord.
But the chassis looks solid (if filthy), all the electrical stuff appears to be there, none of it looks burned or abused.
6SG7 - RF amplifier
6SB7 - Converter
6SG7 (two) - 1st and 2nd IF amp
6H6 - 2nd Detector / AVC / ANL
6SL7 - First audio / CWO
6V6 - Audio out
5Y3 - Rectifier
0D3/VR-150 - Voltage regulator