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LW1DSE > TECH 23.12.17 17:13l 286 Lines 18932 Bytes #999 (0) @ WW
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AA5 Radios (All Amlerican Five)
ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ
Possibly the longest lived consumer electronic product design was
the five tube "AC/DC" AM radio. Virtually every household had at least a few
over the years. These radios were low cost, and one expensive item designed
out was the power transformer. Thus the series heater string, and using the
powerline directly rectified for B+ power. No power transformer also made it
possible for smaller and lighter sets to be made.
(This portion quoted from an article published in the Michigan Antique Radio
Club newsletter by John Reinicke)
In the 20's the crystal set and then the Tuned Radio Frequency, or
TRF, set would provide adequate performance. The complexity and cost of the
Superhet receiver was simply not required. As a result, the Superhet design
appeared only in the most expensive receivers. See a brief description of the
Superheterodyne radio. In the 30's, the situation rapidly changed. Radio had
enjoyed explosive growth and the number of transmitters on the air exceeded
the selectivity of the TRF sets. The 30's also saw an extraordinary economic
circumstance and the manufacturers of radios realized the need to produce low
cost, high performance, receivers. It was now evident the only design that
would provide adequate performance was the Superhet. In order to reduce the
number of tubes required to support the Superhet, manufacturers designed
multipurpose tubes. In April 1933, RCA introduced the 2A7. The 2A7 was the
first pentagrid converter which combined the functions of RF amplifier, mixer,
and oscillator in a single envelope. This tube could then be used with a
pentode as an IF amplifier, a combination diode-triode as a detector-first
audio amplifier and a audio power amplifier to make a complete receiver. Add
to this a rectifier to power the set and you have a high performance receiver
with but 5 tubes. To further improve the receiver, a remote cut off pentode
could be used in the If amplifier so the IF amplifier could be used as a part
of the automatic volume control circuit. The tube line up for this 5 tube
receiver would then be: 2A7, RF amplifier, converter; 58, Remote cut off
pentode, IF amplifier; 55, Diode-triode, Detector-first audio; 59, Audio
output; and 80 for a rectifier. This arrangement uses 2.5 volt filaments and
therefore required the use of a power transformer. This was the prototype
"All American Five."
1934 saw the introduction of the 6A7 and a whole series of 6 volt
tubes to go with it. It was now possible to build an automobile radio or to
combine with a 25Z5 rectifier to build a set without a power transformer.
(See the March 1990 Chronicle article, Ballast). With the elimination of the
power transformer, it was now possible to have a truly low cost, high perfor_
mance receiver. There are those who argue the series filament version became
the classic all American Five.
(end quote) -----
The tube heaters were wired in series, sometimes with a "ballast"
resistance added to make the total voltage drop across the entire string add
up to that of the powerline, around 120V. All the tubes needed to have the
same heater requirement for this to work. All tubes had indirectly heated
cathodes.
Early versions of the five tube radio used the same small signal
tubes (RF, IF, non-power audio) as transformer sets used. Tubes like 6A7, 6D6,
75, 6F7 and newer ones like 6SK7, 6SQ7. And an extra "tuning eye" 6E5 tube if
desired (- George Gonzalez). All these had 300 ma heaters. To make an "AC/DC"
radio, you would just need specially designed audio output and rectifier
tubes. Like the 43, 25L6, 25Z5 and 25Z6. That would be only two new tubes to
be developed (per radio chassis design) to make an AC/DC set. These had
higher voltage heaters, but the same current (300mA) as the small signal
tubes above. Power handling tubes like audio outputs and rectifiers need
bigger cathodes and more heater power to operate. If current is the limiting
design factor, increase the voltage to get more heater power.
But all the heaters in a series string in the above didn't add up to
enough voltage to be fed directly off the powerline. So some sort of additio_
nal voltage dropping resistance was used. Either a power resistor, "ballast
tube" or resistive wire in the power cord was used. I don't know if anyone
used a power resistor housed in a "wall wart" (calculator charger style) power
plug.
One of the above mentioned rectifier tubes, the 25Z6, is a pair of
diodes, used in a voltage double circuit. This gets you a B+ of around 250 to
300 volts. Might make "translating" a design from a power transformer design
to a "hot chassis" design. Not "AC/DC", voltage doublers won't work off of a
DC supply.
Later on, to reduce waste heat in ballast tubes or resistors, the 150
mA tubes were developed. By this time, the 5 tube AC/DC radio was a popular
product, so it was worth while to create new tube designs. Basically, the 6V,
300mA heater signal tubes had their heaters replaced with ones that needed
12V at 150mA. "Tuning eye" tubes at 150 mA heater for consumer radios did
exist. There's the 6AB5 / 6N5. Heater of 6.3V @ 150ma. And the 1629, heater
of 12.6V @ 150ma. But they were rarely used. The Airline model 93WG602B used
the 6AB5. But the common 150ma AA5 tubes used the same power as the 300ma AA5
tubes. And the 25L6 became a 50L6 the same way, 2x voltage, 1/2 current. A
new design overall was the rectifier tube, the 35Z5, with a tap on the heater
to operate a pilot light. And the total added up to the powerline voltage, so
no wasted heater string current thru a dropping ballast. Saved 18 watts of
power that used to be 18 watts of heat to get rid of. And conserved some
energy, but no one worried about that until the mid seventies. It looks like
this occurred in about 1940. All these were octal socket tubes. Loktal ver_
sions appeared at about the same time, also.
Brief superheterodyne description
So much for the heaters for now. Early sets were TRF's (tuned radio
frequency) that just amplified the radio station's carrier frequency, detec_
ted it down to audio, and amplified it. This design would need to have 3 or
so LC circuits that would "track" each other as you tuned across the band.
And with gain stages between, you had to be careful that the amplified signal
at the detector didn't leak back into the antenna, or else you'd hear yourself
instead of a signal. Later on, the superheterodyne radio was invented, and is
still the preferred architecture for modern radio receivers. A basic superhet
receives the radio station with an antenna LC circuit, heterodynes it with a
supersonic (thus "superheterodyne") locally generated frequency, and the dif_
ference of the station carrier frequency and the local oscillator would be the
intermediate frequency (IF). After this conversion, a narrow fixed bandwidth
and frequency gain stage was designed to amplify the signal. Easier to design
such a stage instead of a TRF circuit of the same gain. It also helps that
leakage form the IF won't be "heard" by the front end antenna LC circuit,
because it's a way different frequency. Special frequency changing tubes were
developed to generate and mix the local oscillator frequency with the radio
station carrier to generate the IF. The 6A7, 6A8, and 6SA7, and later the
12SA7 are "pentagrid" converter tubes for this purpose.
Tubes with variable gain were used in IF amp stages, so automatic
volume control (AVC) could be done. Decrease the gain on strong stations so
you don't get blasted out when tuning from a weaker station, and also avoid
distortion overload from the strong station. Tubes like 6K7, 6D6, 6SK7, and
later 12SK7 were variable gain tubes. Usually called "remote cutoff" pentodes,
as the tube wouldn't linearly cutoff current flow like a constant gain tube
("sharp cutoff") would. Yes, these remote cutoff tubes would not be usable in
an audio amp, but these tubes lived in IF strips, where only a narrow band_
width of frequencies were to be amplified, and harmonic distortion products
fell outside the bandwidth of the output IF filter, and were thus ignored.
The audio detector tube would also measure the signal level, and thus could
be fed back to the remote cutoff pentode IF tube. And also to any variable
gain tubes at the front end of the radio. The audio detector diode was arran_
ged to create more negative voltage for strong signals, and more negative
voltage reduces the gain of the remote cutoff tubes.
Once the audio is detected, it needs to be power amplified to drive
a speaker at reasonable volume levels. A triode signal gain stage feeds the
power tube, to generate about 1 watt of audio power to the speaker. The audio
bandwidth is narrower than modern hi-fi stereos. And the speaker was fairly
efficient, so not much power was needed. To a casual listener, if you limit
the low frequencies and the highs at the same time, the listener won't really
notice. The extreme example of this is the telephone, 300 to 3000 Hz. AA5
radios do about 150 to 5000 Hz. Hi-Fi stereos do about 20 to 20000 Hz.
The five tube AM radio didn't much vary after the 150 mA heater tubes
were introduced around 1940 or so. Those were the octal series of tubes. The
12SA7 converter, 12SK7 IF amp, 12SQ7 audio detector and signal amp, 50L6 audio
power, and 35Z5 rectifier. Just after WW2, the miniature 7 pin tubes were
introduced. Miniature tubes were used in the war, but didn't hit the consumer
market until after. The 12BE6 converter, 12BA6 IF amp, 12AT6 audio detector
and signal amp, 50B5 audio power, and 35W4 rectifier. The 50B5 had its plate
next to the heater, but that made for too much voltage between these pins and
UL and similar safety agencies didn't like this. The 50C5 was a rearrangement
of the pinout to solve this safety concern (- George Gonzalez.) Another va_
riation, the "loktal" tube, had its own versions of these, 14Q7, 14A7, 14B7,
50A5, and 35Y4, respective functions. By this time, the AA5 acquired its
designation, the "All American 5" from ww2 surplus tube dealers who sold to
hobbyists (- Doug Houston). You sometimes find AA5 radios using a mix of
octals and loktals, or octals and mini's. Doug MacDonald tells of an AA5 that
used a mix of octals, loktals and mini's. A Philco 81-122, using 7A8, 12BA6,
14B6, 50L6 and 35Z5. Most likely reason for this grouping of tubes was what
they could purchase enough of inexpensively to make radios at the time.
The last version of the AA5 tube line-up was the 100 mA heater
string, introduced in the early sixties. Saved an extra 6 watts of heater
power, but the tubes took a little longer to warm up, and the audio output
power was a bit less. The signal handling tubes were 18V at 100 mA heaters,
so those used the same amount of power as the 12V tubes on the heaters. All
had the same pinouts as the 150 mA versions. But these had slight differences
with the 150 mA tubes, so they were assigned their own designations instead
of being called 18BE6 or 18BA6. They were: 18FX6 converter, 18FW6 IF amp,
18FY6 audio detector and signal amp, 32ET5 or 34GD5 audio power, and 36AM3
rectifier (which the RCA tube manual (RC24) says cannot be used to operate a
pilot light, but the Sylvania tube manual (1968) says it can operate a pilot
light). As you can see, the audio out tube had less heater power than the 50V
at 150 mA version had to heat the cathode, thus less audio power output. Also
the rectifier was also had less heater power, but the audio stage drawing
less current allowed a less current capable rectifier to be used.
A compactron tube version was in development, but turned out it
would have cost more to make than the miniature 7 pin tubes already out. See
Electronics World Oct 1960 article page 48 and page 49 on these. A radio
would have used 2 tubes, a converter/ IF pentode tube "40xx10" (my guess at a
likely tube number had it went into production) and a detector/audio driver &
output/rectifier "70xx11". 100 ma heaters. The 56R9, a compactron triode and
power pentode, is listed in the 1973 edition of GE's "Essential Characteris_
tics" manual, page 212. With a heater current of 150mA, this may have been to
be an "AA5" compactron. See a web page of an AM radio I built using compac_
trons. After you make a few tens of millions of something, you find ways of
squeezing the cost to a bare minimum, which is usually just a bit more than
the cost of raw materials.
Sub-miniature tubes were used by the military, but were too expensive
to make for use in AA5 type radios. See the web page for speculation on how
such a radio might have taken shape.
The end of the AA5 radio was in the early 1970's, as stocks of tubes
and related parts were depleted by manufacturers and sellers. By then, many
were made in Japan, and Japanese AA5 tubes were also made in Japan used by
American radio and TV manufacturers. After that, solid state radios, many
using a high voltage audio output resistor and thus were also "hot chassis",
became the preferred technology.
ALL AMERICAN FIVE - TUBE COMPLEMENT (list by John Reinicke)
ÚÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ ³ ³ ³ ³ ³ ³
³CONVERTER³ IF AMP ³ DETECTOR/ ³ AUDIO ³ RECTIFIER³ YEAR ³
³ ³ ³ 1st Audio ³ OUTPUT ³ ³ ³
ÆÍÍÍÍÍÍÍÍÍØÍÍÍÍÍÍÍÍÍØÍÍÍÍÍÍÍÍÍÍÍÍÍØÍÍÍÍÍÍÍÍÍØÍÍÍÍÍÍÍÍÍÍÍØÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ͵
³ 2A7 ³ 58 ³ 55 ³ 59 ³ 80 ³ 1933 ³
ÃÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 6A7 ³ 39/44 ³ 75 ³ 42 ³ ³ 1934 ³
³ ³ 78 ³ ³ 43 ³ 25Z5 ³ 300 mA heaters ³
ÃÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 1A6 ³ 1A4 ³ 1B5 ³ 33 ³ ³ ³
³ ³ 34 ³ ³ ³ ³ ³
ÃÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 6A8 ³ 6S7 ³ 6Q7 ³ 6K6 ³ 5Y3 ³ 1935 ³
³ 6K8 ³ 6K7 ³ ³ ³ ³ First octal ³
³ ³ ³ ³ ³ ³ sockets ³
³ ³ ³ ³ 6L6 ³ 6X5 ³ 1937 ³
³ ³ ³ ³ ³ 0Z4 ³ ³
ÃÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 6SA7 ³ 6SK7 ³ 6SQ7 ³ ³ ³ 1939 ³
³ 12A8 ³ 12K7 ³ 12Q7 ³ 35L6 ³ 35Z4 ³ 150 mA heaters ³
³ 7A8 ³ 7B7 ³ 7C6 ³ 35A5 ³ 35Z3 ³ First Loktal ³
³ ³ 7A7 ³ 7B6 ³ ³ ³ sockets ³
³ 1A7 ³ 1A4 ³ 1H5 ³ 3Q5 ³ ³ ³
ÃÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 12SA7 ³ 12SK7 ³ 12SQ7 ³ 50L6 ³ 35Z5 ³ 1940 ³
³ 1R5 ³ 1T4 ³ 1U5 ³ 1S4 ³ ³ First Miniature ³
³ ³ ³ ³ 1T5 ³ ³ sockets ³
ÃÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 1LA6 ³ 1LG5 ³ 1LD5 ³ 1LA4 ³ 117Z3 ³ ³
³ ³ ³ 1LH4 ³ ³ ³ ³
ÃÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 12BE6 ³ 12BA6 ³ 12AV6 ³ 50B5 ³ 35W4 ³ 1946 ³
³ ³ ³ 12AT6 ³ 50C5 ³ ³ ³
³ 14B8 ³ 14A7 ³ 14B6 ³ 50A5 ³ 35Y4 ³ ³
³ 12GA6 ³ 12EA6 ³ 12FM6 ³ ³ ³ mid to late 50's ³
³ 12AD6 ³ 12AC6 ³ 12AJ6 ³ ³ ³ 12V B+ tubes for ³
³ 12AG6 ³ 12AF6 ³ 12FK6 ³ ³ ³ car radios, same ³
³ 12FA6 ³ 12BL6 ³ 12AE6 ³ ³ ³ pinouts as their ³
³ 12EG6 ³ 12DZ6 ³ 12FT6 ³ ³ ³ AA5 counterparts ³
³ ³ 12CX6 ³ ³ ³ ³ ³
³ ³ 12EK6 ³ ³ ³ ³ ³
³ ³ 12CY6 ³ ³ ³ ³ ³
³ ³ 12EZ6 ³ ³ ³ ³ ³
³ ³ 12CN5 ³ 12EL6 ³ ³ ³ different pinouts ³
³ ³ 12DK5 ³ ³ ³ ³ ³
ÃÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 18FX6 ³ 18FW6 ³ 18FY6 ³ 32ET5 ³ 36AM3 ³early '60's ³
³ ³ 18GD6 ³ ³ 34GD5 ³ ³ 100 mA heaters ³
ÃÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 26D6 ³ 26A6 ³ 26C6 ³ ³ ³ Military tubes ³
³ ³ 26CG6 ³ 26BK6 ³ ³ ³ 70 ma heaters ³
ÃÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 56R9 150 mA compactron triode/ power pentode tube, early '70's? ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
GE compactrons never released:
"40xx10" converter/IF "70xx11" detector/audio driver & output/rectifier
100ma heaters See Electronics World Oct 1960 article page 48 and
page 49 on these.
ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»
º Compilled from Wikipedia.com . Translatted to ASCII by LW1DSE Osvaldo º
º F. Zappacosta. Barrio Garay, Almirante Brown, Buenos Aires, Argentina. º
º Made with MSDOS 7.10's Text Editor (edit.com) in my AMD's 80486. º
º November 11, 2013 º
ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ
ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»
º Osvaldo F. Zappacosta. Barrio Garay (GF05tg) Alte. Brown, Bs As, Argentina.º
º Mother UMC æPC:AMD486@120MHz 32MbRAM HD SCSI 8.4Gb MSDOS 7.10 TSTHOST1.43C º
º 6 celdas 2V 150AH. 18 paneles solares 10W. º
º lw1dse@yahoo.com ; lw1dse@gmail.com º
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