Note
This article chronicles the historical development, design evolution, and technical specifications of external power supplies produced by the National Company, Inc. from 1927 through 1950.
Under the engineering leadership of James Millen, National pioneered the use of isolated, external power units to ensure hum-free shortwave radio reception.
The text details the progression from early "B" battery eliminators to combined AC heater/plate voltage packs, categorized into distinctive "doghouse" table models and various rack-mounted configurations.
Key models—including the 7180, 5880, 5897, 697, and the military-grade CNA-20090—are cataloged alongside their matching iconic receivers, such as the SW-3, FB-7, HRO, and RAS. Finally, the author provides practical guidelines and safety warnings for contemporary collectors attempting to restore and safely operate these vintage power systems.
7180 1927 Heavy-duty "B" eliminator. The first "doghouse."
718-AB 1927 "B" voltages + 2.5 & 5 V filament windings.
3580 Velvet B 1929 3 adjust. + 1 fixed "8." For the SW-4 Thrill Box.
SW-5 Power Unit 1930 Low-hum. Product of Millen/Kruse research.
5880-AB 1931 4-prong power socket; for HF receivers like SW-3.
5880-AB-S 1932 5-prong socket with 2 "B" voltages. For the SW-58,
ACSW-45.
GR-SPU 1932 Rack-mounted. For AGS; later the HRO.
GR-DPU 1932 Rack-mounted. Double supply; for 2 receivers like
AGS/SW-58C.
5887-AB 1933 For the FB-7; 180 VDC, 2.5 VAC.
5897-AB 1933 For FB-7, HRO, H RO Jr.; 240 VDC, 2.5 VAC.
5886-AB 1933 For 6-V receivers (SRR, 1-10, etc.); 180 VDC.
SPC 1936 Rack unit: combo speaker, power, coils for HRO.
686 1939 Vibrator pack, 6-V; 165 VDC @ 50 mA. 6X5 or OZ4
tube. # 1286 for 12 V.
SPU-686 1939 Rack version of the 686.
697 1939 Same as #5897, except 6.3 VAC.
SPU-697 1939 Rack version of the #697.
5856 1939 For the NHU receiver; 200 VDC, 6.3 VAC.
CNA-20090 1939 For the Navy RAS version of the HRO; rack-mounted.
5Z3 tube.
CNA-20089 1939 25-I-lz version of CNA-20090.
5886 Version II 1941 General utility pack; 240 VDC, 6.3 VAC.
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Model Power Supply
1-10, 1·10A 5886
ACSW-3 (2.5 V) 5880-AB
ACSW-45 5880-AB·S
AGS GR·SPU or GR·DPU
FB-7 5887-AB or 5897-AB
HFS 5886 or 686S
HRO (2.5 V) GR-SPU or 5897-AB
HRO (6 V) 5886-AB or 697
HRO (12 V) 1286
HR0·5R SPC (option) or 697
HROJr. (2.5V) 5897-AB
NHU 5856
RAS CNA-20090 (or -20089)
R-211/U SPU·697
SRR 5886·AB
SW-3U (6 V) 5886
SW·4 3580
SW-58 5880·AB·S
SW·58C GR·DPU
