VW Motorola Tube and “Big M” Radios…1955 through 1963



VW Motorola Tube and “Big M” Radios…1955 through 1963

Langenwalter; 10-10-10

Auto radios evolved dramatically during the mid 1950s through the early 1960s. Tube radios advanced to compact transistor electronics with “Instant On” capability. The predominance of “Manual” non push button radios transitioned to “Automatic” radios with push buttons. Off the shelf “Universal” radios with “Installation Kits” advanced to radios designed for a specific car.

Motorola “Big M” radios have model numbers of 5M, 6M, 7M and 8M. The Big M term is thought to originate from the Motorola “M” insignia found on the Volkswagen installation faceplate. Information in the Sams Photofact publication indicates the “M” (Manual?) models were manufactured from 1955 through 1958. Beginning in 1957, Motorola produced a series of “VWA” (Volkswagen /Automatic?) radios with station selection push buttons.

In 1960, the Bendix Corporation produced Sapphire radios labeled with Designed and built exclusively for Volkswagen Distributors in the United States of America. It wasn’t until 1964 that Motorola produced Sapphire radios with this label.

5M, 6M, 7M and 8M Volumatic Radios

Motorola model numbers 5M, 6M, 7M, and 8M have similar case size and electronics. These radios are called Volumatic radios with “Motorola volumatic” displayed on the dial. The electronic design uses a mechanical vibrator tube to produce high voltage (~200 volts) through an oscillator, transformer and rectifier circuit. The 200 volts used to power tube grid elements. Vibrator tubes have contact “points” which wear out with use and commonly need replacement along with the buffer capacitor. The vibrator tube also has a low volume but audile “hum”.

Sams Photofact lists “M” radios as Universal models indicating they were sold with installation kits made for various car models. There are 6 and 12V models with “-12” appended to the 12V model number.

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5M & 5M-12 Universal

▪ 6 Volt AM radio rated 5.6 Amps at 6.3 Volts DC

▪ AR-5; published February, 1956

▪ Dial; 34B533980 with “Motorola-volumatic”

▪ Knobs 36B355119 (Bullet Style), 120 Dummy and 121Tone

▪ Tubes: 6BD6, 6BE6, 6BD6, 6CR6, 6AQ5, 6X4

▪ Mounts 7B536013 (L), 7K536015 (R)

▪ Rear Mount 7C536020

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6M, 6M-12 and Universal

▪ AM Manual Radio

▪ AR-6; page 169 published April, 1957

▪ Dial; 34B533980 “Motorola volumatic”

▪ Knobs 36B536499 (“Flat Chrome Inset”), 569 Dummy and 570 Tone

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8M

▪ 6 Volt AM radio rated 4.8 Amps at 6.3 Volts DC

▪ AR-8; page 185, published December 1958

▪ Dial; Motorola volumatic

▪ Knobs; 36B540048 (“Bullet Chrome Inset”), 051 Dummy and 050 Tone

VWA7, VWA8, VWA60 Volkswagen Push Button Radios

The VWA model radios are 6 volt, AM, Push Button radios with volumatic electronics. The VWA7 radio was made specifically for 1953 to 1957 Volkswagens with 3 hole dash radio opening. The VWA8 and VWA60 radios were apparently made for 1958 and later Type I Volkswagens with 1 3/4 by 7” radio opening located mid dash. These radios are flipped over with push buttons above the dial which is likely necessary to provide clearance for the wiper motor.

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VWA7

▪ 6 Volt AM radio rated 5.6 Amps at 6.3 Volts DC.

▪ AR-7; page 169, Published February, 1958

▪ 1953 thru 1957 Oval Volkswagens with 3 hole dash

▪ Knobs; Ivory with Chrome Center 36K542194

▪ Metal Tone 36B522020

▪ Metal Dummy 36K542005

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VWA8

▪ 6 Volt AM radio rated 5.4 Amps at 6.3 Volts DC

▪ AR-12; page 129 published March, 1961

▪ Dial; “Motorola volumatic”

▪ 1958 and later dash with 1 3/4 x 7 1/16” opening

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VWA60

▪ 6 Volt AM radio rated 5.6 Amps at 6.3 Volts DC

▪ AR-13; page 101, published October, 1961

▪ Dial; “Motorola volumatic”

▪ 1958 and later dash with 1 3/4 x 7 1/16” opening

10M and VWM60 “Transistor Powered” Radios

The 10M and VWM60 radios were an advancement from the volumatic design to “transistor powered” radios which is also written on the dial. The earlier vibrator tube electronics were replaced with transistorized oscillator and rectifier circuits for the radio’s high voltage supply. A power transistor was also used in the radio’s audio output circuit, however tubes remained in the radio frequency (RF) and intermediate frequency (IF) circuits. The troublesome vibrator tube was eliminated; however the hum or low volume whine remained. These radios are often called Hybrid radios due to the combination of transistor and tube electronics.

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10M

▪ 6V AM radio rated 2.5 Amps at 6.3 Volts DC

▪ AR-13; page 111, published October 1961

▪ Big M compatible case and dial.

▪ Bullet Chrome Knob 36B540048, 051 Dummy and 050 Tone

▪ Dial 34B541017 “Motorola transistor powered”

▪ 4 Tubes; 6BE6, 6BA6, 6CR6 and 6BF6

▪ 2 Transistors Oscillator and Audio Output MN73

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VWM60

▪ AR-13; page 105, published October, 1961

▪ Dial 34B543390 “Motorola transistor powered”

▪ Ivory Knob with Chrome Center 36K542973

▪ Metal Tone 36B522020

▪ Metal Dummy 36K5420054 Tubes; 6BE6, 6BA6, 6CR6 and 6BF6

▪ 2 Transistors Oscillator and Audio Output MN73

VWA63 and VWM63 “All Transistor” Radios

The VWA63 and VWM63 models have no tubes and use solid state germanium transistors.

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VWA63 and VWM63 (not pictured)

▪ 6 Volt, AM, 7 Transistor radio rated 1 Amp at 6.3 Volts DC

▪ AR22 pages101 and 106

▪ ’58 to ’63 VW

▪ Dial; 34B64615A01 “MOTOROLA ALL TRANSISTOR”

▪ radio

12 Volt “MX” Tube Radios

The “MX” models (7MX, 8MX, 10MX, 11MX) are interesting radios for Volkswagens converted to 12 volt. These radios use 12V volt tubes which don’t require high grid voltages. These tubes eliminate the troublesome vibrator tube and noisy oscillator electronics. The radios have similar case configuration to the M models so they can use the Big M installation kit components.

7MX

▪ 12 Volt AM radio rated 2.0 Amps at 12.6 Volts

▪ AR-7; page173

▪ 5 Tubes; 12DE8, 12AD6, 12AF6, 12F6, 12K5

▪ 1 Transistor; 2N178 Audio Output

8MX

▪ 12 Volt AM radio rated 1.4 Amps at 12.6 Volts

▪ AR-9; page 149

▪ 5 Tubes; 12BL6, 12AD6, 12BL6, 12F8, 12K5

▪ 1 Transistor; 2N176 Audio Output

10MX

▪ 12 Volt AM radio rated 1.3 Amps at 12.6 Volts

▪ AR-12; page 133

▪ 4 Tubes 12BL6, 12AD6, 12BL6, 12F8

▪ 2 Transistors; MN73 Audio Driver and 2N176 Audio Output

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11X

▪ 12 Volt AM radio rated 1.2 Amps at 12.6 Volts

▪ AR-16; page 109

▪ Motorola Transistor Powered

▪ 3 Tubes 12AD6, 12BL6 and 12F8

▪ 2 Transistors; MN53 Audio Driver and 2N176 Audio Output

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