[Boatanchors] National NC-101X Adventure and Questions

[Freeberg, Scott (STP)]

I just bought a gorgous NC-101X from Don Merz and it arrived Thursday, just in time for a weekend NC-101 adventure :)   Unfortunately I was down with the flu and didn't even know it arrived.  Saturday I felt pretty good, the girls went shopping, I was still recovering so there was no 'honey do list', which meant RADIO DAY :->>>> Spent the whole day with the 101X.  Also spent a few hours on Sunday as well.  So I thought I'd share my 101X restoration adventure with you, plus ask a few questions.

Opened the lid and saw the chassis and parts were really really nice, surprising nice for a 67 year old radio. I did go in there with the brush and vaccum, and cleaned out the dust and cobwebs.  I pulled the tubes, cleaned the grime off, put a dab of DeOxit on each pin, put em back in.  I should have tested the tubes at this point but for some reason decided not too.  I pulled off the bottom and looked around.  Nice, dusty, cobwebs, few bugs, so went in there with a brush and vacuumed it out as well.

The moveable catacomb coil box is a sight to behold.  That must have cost a fortune to make.  Anyway, it barely turned, no doubt due to the old and stiff grease on the gears, and no grease on the sliding bar.  I cleaned off the old grease, put new grease on, lubed the shaft bushing, greased the sliding bar, wow, turns pretty good now.  

The PW dial turned roughtly with a kink every revolution. I removed the dial and started cleaning the system. I lubed up the variable capacitor as necessary and put DeOxit on the 6 or 8 rotor contact points.  I didn't notice much improvment in tuning.  I opened the PW drive box.  I've never seen one before so it was fun finally seeing one. Yuck, old sludgy grease..  I'll bet I spent 45 minutes working in that little PW drive box with a stiff short bristle brush and WD-40, getting that old stuff off the gears.  Then I put new grease on and closed it up.  I then turned the radio so the front panel shaft bushing was facing up, oiled it, and let it soak in for a while.  

The PW dial was a NOS black dial.  Don told me the new dial had been installed because the original had plating missing, and luckily for me, he included the original silver dial in an envelope.  I'm more of an original kind of guy, so I looked over that original silver dial, and I thought it looked great.  Yes the plating was worn in that area just beyond the knob, for about an inch, but the radio was calling out for the original knob.  So I cleaned the old stiff grease out of the silver PW dial, raided the new PW dial for the springs, the put the silver dial back together.  At first I looked at the two dial pieces, the knob, and springs, and wondered where in the heck the springs went.... Thanks to the generousity of another ham who scanned the PW dial instructions and put them up on BAMA, I was able to see how it went together.  

I plopped the PW dial back on the shaft and gave her a spin.  Oh my!  I was shocked at how smooth the tuning was, and no kink either.  It's like I spread 'buttah' on the mechanism :)  

The LV fuse was missing.  This was not a good sign.   I wondered if it was missing because of some serious problem...  I didn't have any documention that mentioned fuse values so I plopped in a 4 amp fuse.  I need to find out what the right value is supposed to be.

In spite of my better judgement, I powered up the radio before just flat out replacing the hv caps.  I measured 276 vac at the hv filter.  Oops.  The value of good judgement was confirmed, though not followed...  I didn't want to mess with removing chassis mounted cans so I just clipped the wires, left the cans in place, installed some new electrolytics under the chassis.  I found some excellant mounting spots and put the caps in.  Only when I was all done did I make the discovery of why there were no tall parts under the chassis.  I looked at that moveable coil box, then looked at my caps, and realized there was an unanticipated problem :)  I moved the coil box over the caps and noted them making contact...   I made a few changes and have all three electrolytics flattened against the chassis.  This time I measured less than 1/2 volt AC at the filter. 

I found the last electrolytic sitting in the upper left corner, hidden by the coil box.  It was a big metal cylinder cap, 10 mfd at 50 volts.  It was riveted to the chassis, so I just removed the connection and soldered in a 10 mfd 160 v cap.  I note that the new cap is maybe 1/30th the volume of the old cap.  

I powered up the 101X and soon heard cw, sans BFO though.  About two minutes later the BFO showed up and I listened to beautiful cw around the bands.  SSB sounded good too.  Later the bfo disappeared. I tested the BFO tube, and feeling stupid about not testing all the tubes before, tested the rest.  All tubes were good.  So I checked the BFO switch, hoping maybe the oscillator wasn't turning on.  Bingo.  The switch was infinite resistance in both positions.  I removed the switch, held it facing up, sprayed DeOxit around the ball, and worked the mechanism.  This this it yielded 0 ohms, but in both positions.  Oops, too much.. I shook out the DeOxit, still 0 ohms.  So I ended up blowing on the switch like a straw, flushing out excess DeOxit.  Then it worked fine.  Its not like any switch will work in that position.  The shaft is straight, short, and notched.  Turned the 101X back on, and the BFO worked FB.  

The signals sounded beautiful from that huge speaker cone and pair of 6V6's in P-P.  The cw signal would drift though, noticeably.  I tried to back off the RF gain, like I do with the 75A-1 where I run AF max and lower RF.  At '10', I had full gain, but by 8.5 I had 0 gain.  I removed the pot and found that it had a removable cover.  Popped the cover and saw the guts.  The wirewound wire only ran about 1/2 around the pot, plus at that 8.5 spot the resistance changed abruptly.  I cleaned the elements but got the same results.  So I'll have to replace the pot.  I don't know the value of it yet.  It's a 0.25" diameter round shaft, with a 0.5" shaft length, and 0.5" thread length.

The 6E5 green tuning eye didn't work.  I did check the connector and it seemed to have the proper voltages.  I checked the 6E5 on the TV-7 and it didn't respond at all to the open test and closed test, so I'll have to look around for one of those.  Anyone have a 6E5?

I spent some time Sunday afternoon tuning around 20 meter and 40 meter cw and ssb.  Wow, this 101X is an incredible receiver.  Besides looking like a million bucks, it has beautiful sounding signals, incredibly smooth tuning, I love it!  Once I finish the restoration of the 101X, then I can finish building the power supply for my 1935 Gross CW-25 transmitter.  Then I"ll be putting this pair on the air for some fun 1930's operation!  

So that was my 101X adventure so far.  It was a fun day and interestingly enough, the 101X wanted to be restored and put on the air.  
73, Scott WA9WFA