12 volt valves - as in 12 volt h.t. - were introduced in the late 1950s specifically for use in car radios. They made their first appearance in a British set in 1958/1959.
A few sets (usually portables) used conventional valves - either mains or battery - with transistors for audio output. In addition, there were other sets produced for more specialised markets. All the sets used similar transistors (there weren't many about then, you know) and most will be familiar to anyone associated with radio and electronics. However, one type - the OC16 and its equivalent V30/20P - might cause confusion due to the unusual lead-outs. Click here to see copies of some 1957 drawings.
There were two main 12V-valve line-ups - British and American.
Brimar sold the American series in the U.K. whilst Mullard produced
and sold the British types.
As you will see, both British and American companies used both series
of valves.
Typical British valve line-up:
Typical American valve line-up:
Here are all the hybrid sets in chronological/manufacturer order as listed in Radio and Television Servicing, volumes 1956-57 to 1963-64. (There are no hybrid sets listed in other volumes as far as I know).
There is an alphabetical list below.
Layout of entries:
Manufacturer, model (volume:page)
Valve line up
Transistor line up
Notes
Grundig, 200 (1956-57:101)
DK96, DF96, DAF96, DF97
Matched pair OC72
LW/MW/SW portable. DF97 triode connected audio driver.
Pye Telecommunications, TCR16 (1956-57:211)
12BE6, 12BA6, PCL83
Matched pair V30/20P, V30/20P
LW/MW car radio. PCL83 pentode section audio driver.
Third V30/20P transistor used as a d.c. to d.c. converter to generate
85V h.t. for the valves. Up to 6W audio output.
Marconiphone, P60B (1957-58:152)
DK96, DF96, DAF96
Matched pair OC72
LW/MW portable.
HMV, 1410B/1410G (1958-59:140)
DK96, DF96, DAF96
Matched pair OC72
LW/MW personal portable. 4.5V l.t. for heaters and audio output.
Models differ in case design only.
Pyeway (Pye Telecommunications), TCR1000 (1958-59:231)
ECH83, ECH83, EBF83, EF98
V30/20P or OC16
MW plus 1500m fixed, car radio.
Ekco, CR901 (1959-60:75)
ECH83, ECH83, EBF83, EF98
OC72 (driver) plus OC16 (output) or single OC16W
LW/MW car radio.
Motorola, TR127/TR227 (1959-60:162)
ECH83, ECH83, EBF83, EF98
2N351/MN25 (model TR127) or matched pair 2N351/MN25 (Model TR227)
MW plus 1500m fixed, car radio. Single-ended output or push-pull output
stage as separate unit with connecting lead.
Radiomobile, 40T/41T (1959-60:227)
ECH83, ECH83, EBF83, EF98
2N178/OC19
LW/MW car radio. Model 41T similar to model 40T but with polarity selector.
Radiomobile, 42T/42TC (1959-60:228)
ECH83, ECH83, EBF83, EF98
2N178/OC19
MW only car radio. Similar to model 41T above.
Model 42TC has tone control.
Radiomobile, 400T/401T (1959-60:229)
12AC6, 12AD6, 12AC6, 12AE6, 12K5
2N351
LW/MW car radio. Model 401T similar to model 400T but with
polarity selector. Separate audio stage.
Suffix 'A' indicates standard audio stage, suffix 'R' indicates audio
stage has special fixings for Rover cars (page 231).
Radiomobile, 402T (1959-60:230)
12AC6, 12AD6, 12AC6, 12AE6, 12K5
2N351
MW only car radio. Separate audio stage.
Suffix 'A' indicates standard audio stage, suffix 'R' indicates audio
stage has special fixings for Rover cars (page 231). 3W output.
Ekco, CR903 (1960-61:86)
ECH83, ECH83, EBF83, EF98
OC19
LW/MW car radio. Later model (same model number) in 1961-62 volume page 72.
Ford, 1960 Series, Push-Button (1960-61:130)
ECH83, ECH83, EBF83, EF98
OC19/OC26
LW/MW car radio.
Philips, N3G82VT (1960-61:202)
ECH83, ECH83, EBF83, EF98
OC16, later OC19 (serial numbers 120,001 onwards)
LW/MW car radio.
Philips, N4G93VT (also known as the 493VT) (1960-61:206)
ECH83, ECH83, EBF83, EF98
OC26
LW/MW car radio.
Pye, TCR2000 (1960-61:245)
ECH83, ECH83, EBF83, EF98
V30/20P or OC16/2N115 or OC19/2N350
LW/MW car radio.
Ekco, CR903 (1961-62:72)
ECH83, ECH83, EBF83, EF98
OC19/2N350
LW/MW car radio. Earlier model (same model number) in 1960-61
volume page 86.
Motorola, MI series 707 and 505 (1961-62:166)
12AC6/12BL6, 12AD6, 12AC6/12BL6, 12AE6
OC82D, OC26/2N351
LW/MW car radio. Model 505 is MW only.
Motorola, MI series 808 and 606 (1961-62:166)
12AC6/12BL6, 12AD6, 12AC6/12BL6, 12AE6
OC82D, matched pair OC26/2N351
LW/MW car radio. Push-pull version of Model 707 above. Model 606 is MW only.
Pye, TCR100SU and TCR1000SU/X (1961-62:229)
ECH83, ECH83, EBF83, EF98
V30/20P or OC19
LW/MW car radio. TCR1000SU/X has slightly different case design.
Radiomobile, 500T/501T/502T (1961-62:232)
12AC6, 12AD6, 12AC6, 12AE6
OC82 (OC78 early models), single OC26 or matched pair OC26
LW/MW car radio. Model 501T has polarity selector. Model 502T is MW only.
Models suffix 'A' and 'K' have a single-ended output stage.
Models suffix 'B' and 'L' have push-pull output stage.
Ekco, CR915 (1962-63:96)
ECH83, ECH83, EBF83
OC82D, OC26
LW/MW car radio.
Ekco, CR917 (1962-63:98)
ECH83, ECH83, EBF83
OC82D, matched pair OC26
LW/MW car radio. Push-pull version of the CR915.
Elpico, CR116 (1962-63:125)
12AC6, 12AD6, 12AF6, 12DL8
XC141
LW/MW car radio. Unusual choice of valves - 12AF6 is a pentode
and the 12DL8 is a double diode space-charge tetrode.
Elpico, CR412 (1962-63:126)
12AD6, 12EZ6, 12AF6, 12DL8
OC71, OC26
LW/MW car radio. Another unusual choice of valves - 12EZ6 is a pentode
and the 12FM6 is a double diode triode.
Motorola, 77M (1962-63:214)
ECH83, ECH83, EBF83
OC82D, OC26
LW/MW car radio.
Pye, TCR2000X (1962-63:270)
ECH83, ECH83, EBF83, EF98
OC26/NKT452
LW/MW car radio.
Newmatic, Ten-Four (1963-64:190)
ECH83, EBF83,
OC82D, matched pair OC82
LW/MW car radio. The EBF83 is a reflexed i.f./a.f. amplifier.
Ekco, CR901 (1959-60:75)
Ekco, CR903 (1960-61:86)
Ekco, CR903 (1961-62:72)
Ekco, CR915 (1962-63:96)
Ekco, CR917 (1962-63:98)
Elpico, CR116 (1962-63:125)
Elpico, CR412 (1962-63:126)
Ford, 1960 Series, Push-Button (1960-61:130)
Grundig, 200 (1956-57:101)
HMV, 1410B/1410G (1958-59:140)
Marconiphone, P60B (1957-58:152)
Motorola, 77M (1962-63:214)
Motorola, MI series 707 and 505 (1961-62:166)
Motorola, MI series 808 and 606 (1961-62:166)
Motorola, TR127/TR227 (1959-60:162)
Newmatic, Ten-Four (1963-64:190)
Philips, N3G82VT (1960-61:202)
Philips, N4G93VT (also known as the 493VT) (1960-61:206)
Pye Telecommunications, TCR16 (1956-57:211)
Pye, TCR100SU and TCR1000SU/X (1961-62:229)
Pye, TCR2000 (1960-61:245)
Pye, TCR2000X (1962-63:270)
Pyeway (Pye Telecommunications), TCR1000 (1958-59:231)
Radiomobile, 40T/41T (1959-60:227)
Radiomobile, 42T/42TC (1959-60:228)
Radiomobile, 400T/401T (1959-60:229)
Radiomobile, 402T (1959-60:230)
Radiomobile, 500T/501T/502T (1961-62:232)
The A20 by Ajax Electronics. This was a type-approved marine radiotelephone for fitting to merchant ships and small craft under 1600 tons. Some 200 were sold. The designer published details of an amateur radio receiver based on the A20 in Short Wave Magazine - see below.
Practical Wireless, December 1958, 'A 12V Valve-Transistor Car Radio'. A design using: 12AD6 self-oscillating mixer, 12AC6 first i.f. amplifier, 12AC6 second i.f. amplifier, 12AE6 detector, a.g.c. and audio amplifier, 12K5 audio driver. The audio output stage used a V30/20P or an OC16.
Short Wave Magazine, September 1962, 'Hybrid Receiver For Mobile Operation'. An unusual design using ECH83s to perform all functions except for audio driver and audio output. ECH83 heptode:r.f. amplifier; triode:not used, ECH83 heptode:mixer; triode:local oscillator, ECH83 heptode:first i.f. amplifier; triode:b.f.o., ECH83 heptode:second i.f. amplifier; triode:audio amplifier. The audio driver and output stage had several common transistor types listed. This receiver was based on a commercial design - see the A20 above.
Radio and Electronics Constructor, August 1978, 'The "Hybrid" All Wave Radio'. A most unusual reflex design using a single ECH83 and three transistors. The ECH83 is used as a regenerative detector and audio amplifier. Geoffrey Brown has the full article (together with almost every other circuit by Sir Douglas Hall) on his website at http://www.spontaflex.freeserve.co.uk/. In fact, there are several hybrid designs featured on the site. Well worth a look.
The following is an edited and abridged copy of some posts made
to Glowbugs by Jeff Duntemann.
Reproduced with permission.
Some time ago I found myself with two whole evening hours spare. So I threw together a audio power amp using a 12V "space charge" tube.
Space charge tubes were late developments, created in the mid 1950's to eliminate vibrator power supplies in car radios. They all take 12V on the plate, and considering that they were in use for all of five or six years, they appeared in a multitude of forms and remain abundant to this day. In space charge tetrodes and pentodes, the first grid away from the cathode is the space charge grid, and it functions like an accelerator anode to get the electrons chugging toward that weakly-charged plate. The control grid is actually the second grid away from the cathode.
Car radios using these tubes had final audio stages using early power transistors like the 2N301 and some of the proprietary "doorknob" TO-36 PNP germaniums. Driving such a transistor to a volume that could shout down the road racket took a fair amount of current, and they created a special driver tube that could deliver 30 milliwatts with 12v on the plate.
Here is a list of 12V space charge tubes. I've heard many types are identical and they sub well. This group comes out of the 1963 RCA tube handbook. There may be a few others out there from other manufacturers, but by 1963 this category had peaked and the list contains most of what you're likely to find.
12AC6 remote cutoff pentode
12AD6 pentagrid converter
12AE6 dual diode, medium mu triode
12AE7 dual triode
12AF6 remote cutoff pentode
12AJ6 dual diode, high mu triode
12AL8 medium mu triode, power tetrode
12BL6 remote cutoff pentode
12CN5 remote cutoff pentode
12CX6 remote cutoff pentode
12DE8 diode, remote cutoff pentode
12DK7 dual diode, power tetrode
12DL8 dual diode, power tetrode (diodes have own cathode)
12DS7 dual diode, power tetrode
12DU7 dual diode, power tetrode
12DV8 dual diode, power tetrode (diodes have own cathode)
12DY8 medium mu triode, remote cutoff tetrode
12DZ6 remote cutoff pentode (curves are in 1963 RCA tube handbook)
12EA6 remote cutoff pentode
12EC8 medium mu triode, semiremote cutoff pentode
12EG6 pentagrid amplifier
12EK6 remote cutoff pentode
12EL6 dual diode, high mu triode
12EM6 diode, power tetrode
12F8 dual diode, remote cutoff pentode
12FK6 dual diode, low mu triode (triode curves are in 1963 RCA tube handbook)
12FM6 dual diode, medium mu triode
12FX8 medium mu triode, pentagrid converter
12GA6 pentagrid converter
12J8 dual diode, power tetrode
12K5 power tetrode
12U7 twin medium mu triode
The 12EK6, 12DZ6 and 12AC6 are listed as direct subs in the RCA manual.
My article files for space charge tubes yield the pieces below. Several of these were graciously sent to me by Michael Covington N4TMI, who retrieved them from the dusty stacks at the University of Georgia, Athens.
"Low Plate potential Tubes" RADIO & TELEVISION NEWS, January 1957. Some theory and history from Tung-Sol, including curves on the 12K5.
"Simple 12V Mobile Converter for 75 & 40 Meters" QST, July 1958, Hints & Kinks. Proves out NA4G's contention that "ordinary" tubes work at 12V by showing a 12SA7 metal converter in 12V service with a 3MC crystal.
"Converter Puts FM in Your Car" RADIO-ELECTRONICS, August 1959. Basically a one-page review of the Gonset 3311 broadcast FM converter product. It includes a schematic, which is useful for biasing values and ideas, but coil and some capacitor values are not given. Uses 12EC8, 12EZ6, 12AD6, and 12AL5.
"Design of Mobile Receivers with Low Plate Potential Tubes" ELECTRONICS, August 19, 1960. Useful circuits for the 12EK6 amp and 12AD6 converter, for FM mobile to 180Mhz.
"A 10-Meter Mobile Converter" CQ, August 1963. Uses a 12AD6. No crystal; uses LC tuning. You could lash this up in an hour and it would be fun to try if you have local 10M AM activity.
"A Complete Mobile Package, Part 2" QST, July 1964. Best of the lot. 5-band switched RF amp, converter, and 1600kc IF strip for use into a car radio. Basically the front end for a bandswitched superhet using space charge tubes. Uses our friends the 12EK6 and 12AD6. Part 1 of this series is a nice AM rig with a 2E26 final.
"An Inexpensive Mobile Converter" CQ, issue unknown. I copied this out of my mags for filing without taking note of the issue, but I would guess 60-62 somewhere. Simple circuit with a 12BE6 asnd a 3Mc crystal, converts to 40 and 80. Says 12AD6 will work as well.
Several car radio schematics using space charge tubes are present in a book by Lou Garner called Transistor Circuit Handbook, published by Coyne Electrical School (Chicago) in 1960. However, if you have any of the old Photofacts books for car radios in the period 1957-1964 you'll probably find a bunch of examples. There is also a car radio schematic in back of the 1963 RCA tube handbook. It's also in the 1965 book and may be in others but those are the only two I have.
Robert Casey WA2ISE has a schematic of an AA5 that has been modified to use 12V h.t. tubes. The relevant link is here. More of Bob's pages can be found here.