Something Different - National NC-109

 I need another old SW receiver like I need another hole in my head, but I felt sorry for this old NC-109 when it came up at an auction I attended last summer and nobody wanted to bid on it.  I don't remember what I ended up giving for it, but it wasn't much.

Other than being dirty, it appears to be all there, so let's see what we have:

 Typical dusty, dirty chassis - looks like a layer of nicotine residue, but no rust or mouse damage, and all the tubes are there.  We're off to a good start!

This is interesting.  At the top of the chassis, it looks like someone hacked-in a 40uF electrolytic and 500 ohm wirewound, probably because the multi-section filter cap wasn't doing it's job. Sigh. Kids.  

That was an easy fix, though, and what's cool is that there aren't many tubular paper caps to deal with - National used ceramics for bypassing, and those don't usually fail.

Normally, I like to remove and restuff chassis-mounted electrolytics, but I really don't feel like this rig is worth the effort.  I might change my mind tomorrow, but for now, I've disconnected the can and installed new caps on a terminal strip.

Now for the fun part!  After changing the filters and inspecting for any other obvious problems - time to power it up!  I don't have any pics of this process (not much to see, really) - I use a variac connected to an isolation transformer, and bring it up slowly, watching for any signs of trouble.  This old National fired right up - no magic smoke was released!  Yippee!

At this point, I gave it a quick evaluation, starting a "punch list" of things still needing attention:

1. Band 1 (AM BC) is dead.
2. Strange AVC "pumping" and background noise - mixer?
3. Dirty controls/switches.
4. Main tuning and Bandspread caps stiff - need clean/lube.
5. Rudimentary cosmetics / degrunge.
6. Screw terminals for antenna disconnected/rerouted to added SO-239 - need to be restored (why do people do this?)

Nothing looks too bad.  On the good side: 

• It receives: Envelope and product detectors are both working.
• ANL works.
• BFO works.
• Crystal filter/selectivity switch works.
• Dial calibration is reasonably close.
• Only a handful of tubular paper caps and one LV electrolytic (AF cathode bypass) to replace.
• Nothings smoking!

So, barring anything unforeseen, should be able to whack this one out in a few nights.  Wish me luck!!!

73 - Steve