National NC-300 and NC-303 variation info

More photos of NC-300, NC-303, and speakers coming soon.
Send comments and corrections to nick@virhistory.com

METER FACE for NC-303 and NC-300

download pdf file - thanks to Bill W0NG

ADVERTISEMENTS & MISC.

The introduction of the NC-300 was preceded by a highly publicized contest to design the "Dream Receiver" (photos coming soon). The early ads showed a different S-meter arrangement than the production units.
300-sales-bw.jpg (294936 bytes)
Spec sheet 9/56
300-letter-56.JPG (218608 bytes)
Sales letter - 9/56
300-AFG-tag.JPG (7724 bytes)
Tag on AFG control


SERIAL NUMBERS

The serial number is stamped into the top of the chassis just behind the crystal calibrator socket - just lift the lid and take a peek. Please send me e-mail with info on your NC-300 - thanks to all the contributors so far. 

It appears that some early NC-300's had a gray smooth glossy finish on the bezel and/or cabinet - later units had a gray wrinkle finish. Interestingly, it appears the last units made also had a smooth bezel but wrinkle cabinet.

Starting with the 2nd run (460-xxxx) a 20m band mixer image trap made up of C86 and L18 was added. The last run (481-xxxx) had a 330 ohm resistor substituted for the filter choke (L17).
Serial No Bezel Cabinet Filter Choke?
434-0190 smooth smooth yes
434-0373 smooth ? yes
434-0694 wrinkle smooth yes
434-0752 wrinkle smooth yes
434-0827 smooth smooth yes
434-1227 wrinkle wrinkle yes
434-1481 wrinkle wrinkle yes
434-1789 smooth smooth yes
434-1791 wrinkle ? ?
434-1898 wrinkle smooth yes
434-1964 wrinkle smooth no (???)
460-0347 wrinkle smooth ?
460-0518 wrinkle smooth yes
460-0724 wrinkle smooth yes
460-1032 wrinkle smooth yes
460-1089 wrinkle smooth yes
460-1514 wrinkle ? yes
460-1588 wrinkle smooth yes
460-1840 wrinkle smooth yes
460-1852 wrinkle smooth yes
460-1865 smooth smooth yes
460-1888 wrinkle smooth yes
481-0050 wrinkle wrinkle no
481-0205 wrinkle ? no
481-0511 wrinkle wrinkle no
481-0952 wrinkle wrinkle no
481-0998 wrinkle wrinkle no
481-1011 wrinkle wrinkle no
481-1148 wrinkle wrinkle no
481-1176 wrinkle wrinkle no
481-1369 smooth ? no
481-1737 smooth wrinkle no

Choke/Resistor Variants -to tell them apart, lift up the top lid and look at the screw heads just to the left of the power xfmr - no need to look under the chassis.

300-choke-02.JPG (37901 bytes)
Early units
- Two phillips head screws holding L17 choke in place
300-choke-01.JPG (52363 bytes)
L17 choke under chassis
300-nochoke-02.JPG (40180 bytes)
Later units - Two holes + two rivets holding terminal strips for 330 ohm resistor
300-nochoke-01.JPG (49728 bytes)
L17 replacement - 330 ohm resistor under chassis

MANUALS

I have seen 3 different instruction books so far - They match production runs. Please send me e-mail with info on any others.

Publication (on last page) Date Features
SM-3000-ER434 8-55 Does not say "IMPORTANT..." at top of first page
Was 434-xxxx the first production run?
SM-3000-ER460 3-56 "IMPORTANT... READ THE BOOK FIRST"
AFG switch explanation is changed
L86/C86 image trap added
SM-3000-ER481 9-56 "IMPORTANT... READ THE BOOK FIRST"
    added R61 (100K ohms)
    added R62 (330 ohm replaces L17 filter choke)
    added R63 (2.2 ohm in series w/ 4H4-C ballast)
    added C87 (0.22 uf)
Was 481-xxxx the last production run?

 

300-man-0855.JPG (122447 bytes)
ER434 - August 1955
300-man-0356.JPG (125714 bytes)
ER460 - March 1956
 

PAINT FINISHES

NC-300 and NC-303 cabinet sides had light color above, dark below. Top was light. Rear was light.
Note - Some close-ups were done by directly scanning the speakers and may have odd reflections

Click on an image to get a 4X larger version
300-smooth.JPG (41764 bytes)
Early model NC-300
(smooth finish bezel)
another photo
300-wrinkle.JPG (68431 bytes)
Later model NC-300
(wrinkle finish bezel)

late model NC-300 with late model NC-300TS speaker
(both wrinkle finish)
300ts-stripe-01.JPG (37632 bytes)
Early model NC-300TS
(smooth finish paint)

Early model NC-300TS speaker grille - Ads also showed vertical striped grille cloth shown at left
Early model NC-300TS speaker side view - smooth paint matches colors on early NC-300 front panel.
300ts-later-01.JPG (47489 bytes)
Late model NC-300TS speaker with wrinkle paint finish

late model NC-300TS speaker
grille
Late model NC-300TS speaker side view - wrinkled paint matches colors on later NC-300 front panel.
nat-nts2.jpg (86915 bytes)   spkr-nts2-02.jpg (191404 bytes)
NTS-2 speaker that matches NC-303 and NC-400
Note chrome side strip.

NTS-2 speaker speaker grille
NTS-2 speaker matches NC-303 cabinet - wrinkle paint - black portion matches bezel color on front of NC-303. Light color is creamier than front panel gray. Has chrome side strip
nts2-var-01.jpg (125201 bytes)
NTS-2 speaker variant - note different logo & location
grille cloth appears to be the same paint appears to be the same

NTS-1 speaker that matches NC-109 and NC-188. Note lower "two-tone" dividing line, different grille cloth, and no lightning bolt. - Wrinkle paint is close to late model NC-300TS but a little browner maybe.
 NTS-1 grille photo
coming soon 
 NTS-1 side photo
coming soon
NC-300CC Converter Cabinet
NC-303CC Converter Cabinet

For mounting 3 VHF converters
(50 Mc, 144 Mc, 220 Mc)

Both NC-300 and NC-303 paint schemes existed - NC-303CC had chrome side strips and darker gray.

300cc-later-01.JPG (20660 bytes)
Later model NC-300CC with wrinkle paint
 


MORE INFO

Here are some links to more info on the National NC-300 and NC-303

Please send send me e-mail with more links or info on the NC-300 and NC-303 receivers
Thanks - Nick England K4NYW - Chapel Hill, NC