Edelpro Museum
for
Preservation
of Vacuum Tubes and Analog Electronics
Part II – Radio Sets and Equipment
This section includes every
kind of stuff worth of interest, of course in my opinion. It is usually
believed that a collection must show rare pieces by famous designers. On the
contrary I just tried to prevent some sets and pieces of equipment to be
hastily scrapped. Many of them are usually defined in derogatory terms as
‘boatanchors’, as they were just huge piles of scrap metal. Actually they were fine
examples of the state of the art in their time and sometimes their performances
were unsurpassed for many years.
The most prolific period for
electronics starts just before WWII, reaches its peak during the war and goes
to the early sixties, when it starts a fast decline, moving to solid state
integrated circuits and to Asian productions. The huge growth of electronic
devices during WWII is evident when considering that just before the war the
total value of electronic equipment in a military or in an airline aircraft was
less than 4000 US dollars. Here the
most advanced Chinese electronic factory during WWII and its conveyor system.
Few years later, in the mid fifties, a single strategic bomber could carry over
than 750,000 USD of electronics. In fact all we could see aboard before the war
were a radio communication set and a radio direction finder, while just 15
years later we find a lot of avionics, up to autopilot and even no hand carrier
landing systems.
At the beginning, new systems
were hastily devised and designed, in response to the pressing requests of the
military. Over the years, the systems were perfected for the highest
performances and reliability and miniaturized. But they retained two primary
characteristics, the full control by the operator and the full access to every
subassembly and components by technicians. No keyboards, no touchscreens, no
menus, no intelligent peripheral interfaces, no microcontrollers and even no
hidden routines. Even in their simplicity, those vacuum tube based systems were
capable of performing satisfactorily the tasks for which they had been
designed. After all the space era, with its early satellites, started with
computers like the ones below.
|
|
|
A mechanic computing
machine, the Monroe LN-160 about 1940 and the ad for the MOBIDIC, a military
mobile computer from Electronics, December 1957. (Click to enlarge)
German vacuum
tube radios
I started collecting German
radio sets for their accurate design, resulting in reliable operation and in a
remarkable sound reproduction. The quality of these sets can be better
appreciated when compared with similar sets built in Italy in the same days.
Most of the Italian productions had no power transformer, the chassis being
connected to the mains, no built-in antenna, no tone controls, no multiple
speaker system. On the contrary, German radios were fine examples of
engineering with a lot of interesting solution, including:
Ø Low-profile
chassis, with expanded tuning dials.
Ø Power
transformer with insulated chassis; high-efficiency Graetz-bridge selenium
rectifier.
Ø Internal
AM/FM antennas, with AM rotary loopstick.
Ø Keyboard
band/function switch.
Ø Smooth
tuning systems with reduction gears and flywheels; dual coaxial knobs for AM
and FM or a single knob mechanically driven by band switching keys; preset
channels, band spread dials or even with motor-driven auto tuning in some
cases.
Ø Loudness
control plus tone controls and even tone registers, sometimes in addition to IF
variable bandwidth, driven by the same tone control knobs.
Ø Speaker
systems including electrostatic or horn tweeters.
When I started the collection,
AM broadcast stations were already in progress of being dismantled. I focused
then on FM radio sets, which could still be enjoyed today. The drawback for
most of German sets is the poor FM coverage, limited to 100 MHz. Exhibits
include radio sets from the very early introduction of FM, around 1950, to the
late FM-Stereo vacuum tube radios, dated around the mid sixties. It is very
interesting to compare through the years the evolution of the audio section,
amplifier and speaker system, according to the evolution of sound sources.
Actually the very early FM
sets were just AM receivers with an added FM tuner. Program sources a the time
were the old standard-groove shellac records. The design of audio amplifiers
and speakers was still centered on about 5 kHz bandwidth. With the introduction
of microgroove vinyl records, the bandwidth quickly jumped to about 15 kHz.
Speaker systems started to include some tweeters. The early low efficiency
electrostatic types were soon replaced by dynamic cones and even by horn
drivers.
The early approach to the
stereophony, around 1957, was the 3D surrounding sound, with extra speakers
added on both sides, all driven by the same monophonic source. Later, even if
the tuner was still mono, audio section evolved with provision for full
dual-channel amplifier. Stereo sound was only possible when switching to the
record player, to listen stereo records, or even to tape recorder.
We have to wait until the mid
sixties to see full stereophonic sets. First, when the service was still
experimental in very few big cities, we find a simple socket for an optional
stereo decoder, then the decoder was factory installed. Most of these new sets,
known as ‘steuergërat’, came with external speakers, according to the standards
introduced by American Hi-Fi sets. But the Japanese industry was already moving
to full solid-state. After few hybrid solutions, German vacuum tube radios
disappeared from the scene.
The collection well shows the
evolution through some fifteen years, from about 1950 to about 1965, with a
wide overview of models mainly from Graetz and Saba, but also from AEG,
Blaupunkt, Braun, Grundig, Telefunken and others even from other countries. The
exhibits are divided into four major groups:
Graetz
German radios, about 1950 to 1965.
Graetz was a typical German
radio manufacturer. The collection includes several FM vacuum tube models, from
1950 to about 1965, offering a quite complete overview of the technical
improvements through the years.
|
Model |
Year(s) |
Notes |
|
1950 / 1951 |
Rimlock tubes,
electrodynamic speaker, 2 x EF42 tubes in the FM tuner. |
|
|
1951 / 1952 |
Rimlock tubes,
electrodynamic speaker, 2 x EF42 tubes in the FM tuner. EL11 output power amplifier, 6W. |
|
|
1953 / 1954 |
10 tubes, 2 x EL84 push-pull
audio amplifier, 3 speakers. Power save switch. |
|
|
1956 / 1958 |
4 loudspeakers, with 2-way
flute compressor. |
|
|
1957 / 1959 |
EL84 audio amplifier, 2
woofers, 1 mid-range and one 2-way flute compressor. |
|
|
1961 / 1962 |
Stereo AF amplifier, 2x7.5W
push-pull stages based upon EL95 power tubes. 6 speakers. |
|
|
1964 / 1965 |
Solid-state stereo decoder,
stereo push-pull amplifier with 2 x ECLL800, 2 speakers. |
|
|
1964 / 1965 |
Solid-state stereo decoder,
stereo amplifier with a single ELL80, 2 speakers. |
Saba
German radios, about 1952 to 1962.
Saba was well known worldwide
for its top class production.
|
Model |
Year(s) |
Notes |
|
1952 / 1953 |
EL34 audio amplifier, two
speakers. Variable
bandpass. |
|
|
1953 / 1954 |
12W audio amplifier w/ EL12,
two speakers. |
|
|
1954 / 1955 |
EL84 audio amplifier, 2 speakers. |
|
|
1955 / 1956 |
Low-end model, EL41 audio
amplifier, single speaker. |
|
|
1956 / 1957 |
10 tubes, auto-tuning, 4 speakers. |
|
|
1957 / 1958 |
Build-in record player, EL84
amplifier. |
|
|
1960 / 1961 |
Stereo amplifier, 2 x EL95,
switched in push-pull like circuit when mono. |
|
|
1960 / 1961 |
Auto-tuning, stereo
amplifier, 2 x ECL86 |
|
|
1961 / 1962 |
Auto-tuning, stereo
amplifier, 2 x ECL86 |
More
German brands
Brand
|
Model |
Year(s) |
Notes |
|
AEG |
4075WD |
1955 / 1956 |
SW band spread, EL84 audio
ampl, 3 speakers |
|
Blaupunkt |
Virginia 2430 |
1957 / 1958 |
EL84 audio amplifier, 3 speakers |
|
|
1958 / 1959 |
SW band spread, 3 speakers,
push-pull EL95. |
|
|
Braun |
1956 |
Four bands, UKW, 7 tubes |
|
|
|
1961 |
Four bands, 9 tubes plus
selenium rect. |
|
|
Grundig |
1953 |
Variable bandpass. 2,
electrostatic and dynamic, speakers, EL12 audio amplifier. |
|
|
|
1955 / 1956 |
5 speakers, EL84 amplifier,
remote control. |
|
|
|
1956 / 1957 |
Graphic equalizer, 4
speakers, EL84 amplifier. |
|
|
|
Steuergerät 6199 |
1960 / 1961 |
Stereo push-pull amplifier,
2 x ELL80, external speakers, graphic equalizer. Mono tuner. |
|
|
1965 / 1966 |
3 tubes, AM/FM, PE record
player |
|
|
Kaiser |
1955 / 1956 |
3 speakers, EL84 amplifier. |
|
|
Metz |
1962 / 1963 |
Mono tuner, stereo
amplifier, 2 speakers. |
|
|
Nordmende |
1964 / 1965 |
Stereo decoder, 2 x ELL80
p/p amplifiers, external speakers. |
|
|
Philips D |
1964 / 1966 |
Stereo decoder, 2 x ELL80
p/p amplifiers, 2 speakers. |
|
|
Tekade |
1954 |
3 AM plus FM bands, 8 tubes |
|
|
Telefunken |
1961 - 1962 |
Stereo amplifier, record
changer, 2 x EL84 amplifier, 4 speakers. |
|
|
|
Opus Studio 2650 |
1963 - 1964 1965 - 1968 |
Vacuum tube and hybrid ‘Steuergerät’ with external speaker
enclosures. |
Italian
and other brands
Brand
|
Model |
Year(s) |
Notes |
|
|
|
|
|
|
Autovox |
1958 / 1959 |
Car radio with automatic
tuning |
___________
Sound
recording and reproducing sets
Another section covers some
top audio components and sets from the late sixties to the very early
seventies, when I tried several alternate solutions, homebrew, French, German,
Japanese, Swedish, Swiss and U.S. components to assemble a top sound
reproduction system. My reference was a small Hi-Fi shop in Naples, Elettronica
Meridionale, run by a true audiophile, Mr. Raffaele Trombone. Thanks to a
switch matrix, one could compare the preferred kind of music sources reproduced
by any combination of record players, pick-up heads, amplifiers and speaker
enclosures. Here I could evaluate brands as AGA, Altec, Ampex, Acoustic
Research, ERA, Fisher, Harman Kardon, JBL, Klipsch, Koss, Marantz, Quad,
Pickering, Revox, Shure, Thorens, Uher and many more. Mr. Trombone was able to
combine components of several manufacturers to offer the best sound system for
every pocket. I remember that my first system was a combination of a Dual
record changer, a Shure pick-up, a couple of AGA bookshelf speaker enclosures
and an Uher tape recorder also used as power amplifier with its internal
monitor amplifier. Mr. Trombone offered a very attractive swap service. I tried
several systems, up to the latest one that I still preserve, as one of the
finest ever done: two Empire Troubador record players, one with an ADC XLM
stereo cartridge and the other with a quadraphonic Empire 4000 pick-up, a
Marantz 3300 control console driving a Marantz 500 power amplifier, a Nagamichi
700 cassette deck and two Klipsch
Enter
the sound recording and reproducing sets
gallery
Country / Mfr. |
Model |
Notes |
|
|
|
|
|
D – Revox |
A77 Tape deck |
|
|
|
B710 Mk II Cass Deck |
|
|
|
B215 Cassette Deck |
|
|
|
B225 CD Player |
|
|
Italy – Homebrew |
EC-7 Stereo Amplifier |
|
|
JPN – Nakamichi |
700 Cassette Deck |
|
|
USA – ADC |
|
|
|
USA – Empire |
|
|
|
|
Complete with 4000D III
cartridge |
|
|
USA – Klipsch |
La Scala K-477 |
Horn speaker enclosures, two
available |
|
USA – Marantz |
|
|
|
|
|
|
|
|
1060 Power Amplifier |
|
|
|
|
Other audio devices or equipment
Country / Mfr. |
Model |
Notes |
|
Germany – AEG |
1953-1955, 9.5 cm/s, 5 tubes |
|
|
Germany – Grundig |
9.5/19 cm/s, 1953 - 1954 |
|
|
|
Tape recorder, 3-speed, 8 tubes. 1964-1966 |
|
|
|
4.75/9.5/19 cm/s, stereo, 6
tubes + semicons |
|
|
Germany - Saba |
600SH Hi-Fi tape
record. |
9.5/19 cm/s, 42 semiconds, 1966 - 1970 |
|
Germany - Telefunken |
9.5/19 cm/s, 7 tubes, 1962 -1963 |
|
|
Germany – Uher |
9.5/19 cm/s, 5 tubes, 3 heads, 1955 |
|
|
France - Supravox |
Garrard record changer, 4
tubes + sel. rect. |
|
|
Italy - Geloso |
19 cm/s, 9 tubes, p/p 6V6,
1954-1956 |
|
|
Italy - Marelli |
RM8 |
9.5/19 cm/s, two tracks, 4
tubes. 1960 |
|
Japan - Akai |
1700 Tape Recorder |
4-track stereo, 4 tubes, around 1968 |
|
|
GX-630 DB Tape Deck |
4-track, 3 motors, 2-speed,
solid-state. 1975 |
|
Japan - Teac |
A-3440 Tape Deck |
4-track, 3 motors, 19/38 cm/s |
|
|
A-4300SX Tape Deck |
4-track, 9.5/19 cm/s, autoreverse |
______
Vinyl records
His
section includes LP records from the sixties and the early seventies. Female
performers are present with over 50 titles by Connie Francis and a complete
overview of Patsy Clyne. Other categories include most of the volumes by Fausto
Papetti and his sax, by Ronnie Aldrich and his two pianos and several 4-Phase
Decca records.
Still
waiting for a complete inventory.
________
Communication
receivers and related equipment
Communication receivers were
the natural evolution of the crystal radio, to listen to worldwide stations. I
was attracted from the idea of listening someone speaking thousands of miles
away. I started with old surplus sets, an Allocchio Bacchini OC8 and a military
BC-
SW receivers range from a
pre-war Hammarlund SP-110, to some military BC-312s and to the well known
SP-600, from a Collins 51J2 to the marvelous R-390A, to the late R-1051/URR,
using only two vacuum tubes, to some solid state receivers from the Italian
Elmer line.
Communication gears also
include some transmitters, as the BC-191, and some transceivers, as the
Wireless Set 19 MKIII and the ARC51, equipping the F-14 Tomcat.
Enter the communication receivers and related
equipment gallery
|
Country / Mfr. |
Model |
Notes |
|
Canada Military |
Wireless Set No.19 Mk III |
SW/VHF transceiver, AM/CW
emission. With antenna coupler and carrying case. 15 tubes. |
|
Italy Elmer |
R-1003
LF/MF/HF rec. |
Digital tuning from 10 kHz
to 30 MHz |
|
|
2 to 30 MHz digital tuning,
LSB, USB, ISB, FSK, AM and CW. 2 tubes. |
|
|
|
SP-520 receiver |
Triple conversion
communication receiver. Solid-state, digital tuning, 2 to 29.999MHz. AM, CW,
FSK, LSB, USB, ISB modes. |
|
|
SR11 receiving system |
SP-520 SW receiver plus
speaker/supply box and RTTY decoder. |
|
|
SP-706/PS preselector |
RF preselector covering from
2 to 30 MHz |
|
|
SP-520/L11
HF/SSB rec. |
2 to 30 MHz, 6-digit tuning.
BITE feature. |
|
|
SP-841/D rec. system |
SP-520/L1 plus SP-706/PS
preselector. |
|
Italy Military |
US BC-312 overhauled with
Italian labels. |
|
|
|
Trasmettitore BC-191 |
US BC-191 overhauled with
Italian labels. |
|
USA – Bendix |
TA12B transmitter |
300-600 kHz and 3-7 MHz. AM,
CW, MCW. Four pre-tuned channels. 40W out power. |
|
USA – Collins |
0.5 - 30.5 MHz in 30 bands,
1MHz each. |
|
|
USA – Hammarlund |
SPR-110LX Super-Pro |
LW/SW receiver, 16 tubes |
|
|
SPR-600JX Super-Pro |
MW/SW receiver, 20 tubes |
|
USA – Military |
AN-ARN6 radiocompass |
Radiocompass receiver with
loop, indicator and remote control box. |
|
|
BC-312-M receiver |
1.5 - 18 MHz AM / CW, 9 tubes. |
|
|
BC-191 transmitter |
200 kHz to 12.5 MHz with
plug-in tuning units. 50
to 75 W. 5 tubes. |
|
|
BC-614-E speech ampl. |
Auxiliary amplifier for BC-610 |
|
|
IFF transponder, WWII ABA |
|
|
|
HS-30 Headset |
|
|
|
Airborne transceiver, 225 to
399.9 MHz in 3500 channels, 16W RF output. 8 tubes. |
|
|
|
Personal radio receiver for
combat zones |
|
|
|
SAR RT-159/URC-4 |
VHF/UHF rescue radio
receiver/transmitter. |
|
|
0.5 to 32.5 MHz in 32 bands,
1 MHz each. Digital readout. AM/CW/MCW. 26 tubes. |
___________
Instrumentation
This section includes several
beautiful instruments salvaged from destruction, just because too quickly
become obsolete. It is divided in 5 major families.
Signal
Generators and Frequency Meters
In my early years of electronics
experiences I only relied upon very poor test equipment, as those by Scuola
Radio Elettra. My dream was an accurate and stable frequency source, to check
the calibration of the several receivers I handled at that time. My very early
stable frequency source was a homebrew frequency standard, with 1 MHz crystal
controlled oscillator and two cascaded divide-by-ten multivibrators. I built it
in 1965 and I still preserve its chassis, or what survived the children of a
guard that took care of my country house. Nice job for a guy of just nineteen!
The first accurate generator I found around the mid sixties was a BC-221Q
frequency meter, for which I built a stabilized AC power supply. Unfortunately
it was unmodulated and its maximum frequency was limited to 20 MHz. In the
sixties and up to the early seventies few signal generators were available as
military surplus. Nevertheless I had found some military generators, and a
couple of huge HP 124B counters, capable of operating up to 100 MHz with their
heterodyne plug-in prescalers. Then I decided to give away them all.
In recent years I found
several old frequency generators and counters coming from the dismantling of
old service shops and laboratories. The collection includes a wide spread of
equipment ranging from military WWII test sets to standard generators, to
microwave generators, to radar test equipment, up to frequency meters and
counters. Most of the sets are complete with their technical manuals. Smart
operating principles and remarkable solutions used to enhance performances of
most advanced sets are often focused in the description of each device.
Also available in this section
are some frequency meters, including digital counters. Among these, we can see
a trochotron frequency meter by Van Norman Industries, fully operating and
believed to be a fine example of electronic archeology.
|
Country / Mfr. |
Model |
Notes |
|
|
|
|
|
GB – Advance |
B4A5 RF Generator |
100 kHz to 80 MHz in 6
bands, 3 tubes |
|
GB - Military |
Wavemeter Class D No 1, Mk
II |
1.9 to 8 MHz in two ranges,
heterodyne. 1 tube ARTH2 plus dual Xtal. |
|
Italy – Lael |
Oscillatore 145-C |
140 kHz to 42 MHz in six
bands, 1 tube. |
|
Italy – Mial |
Oscillatore 145 |
100 kHz to 22 MHz in six
bands, 2 tubes. |
|
Italy – Unaohm |
Generatore BF EM33 |
20 Hz to 20 kHz in three
ranges, 5 tubes. |
|
USA – Gen Rad |
Standard Signal Generator 805-C |
16 kHz to 50 MHz in seven
bands, plus aone custom band. 12 tubes. |
|
USA – HP |
Oscillator 200CD |
5 Hz to 600 kHz in 5 bands,
5 tubes. |
|
|
606A
Signal Gen. |
50 kHz to 65 MHz over 6
bands |
|
|
Counter 5245L |
8-digit frequency counter up
to 50 MHz, up to 18 GHz with additional plug-ins. |
|
|
Frequency Divider |
Divide by 100 or by 1K
prescaler, up to 12GHz |
|
|
Transfer Oscillator 5257A |
Prescaler module for 5245L
above. |
|
|
Signal Generator |
1.8 to 4.5 GHz, 6BL6
klystron, 13 tubes. |
|
USA – Measurements |
Signal Generator 65-B |
80 kHz to 30 MHz in six
bands, motor tuning, 12 tubes. |
|
USA – Military |
Frequency Meter |
125 kHz and 20 MHz in two
bands heterodyne. Several
models available. |
|
|
I-72 Signal Generator |
100 kHz to 32 MHz in five
bands, 3 tubes. |
|
|
FM Signal Generator I-208 |
1.9 to 4.5 and 19 to 45 MHz,
film tuning dial, 17 tubes. |
|
|
I-129-B Frequency Meter
Set |
Absorption frequency meter,
1.5 to 40 MHz with 4 LC units. |
|
|
TS-47/APR Test Oscill. |
VHF generator, 40 to 500
MHz, two bands |
|
|
TS-174 Frequency Meter |
VHF version of BC-221. 20 to
250 MHz in 2 bands. |
|
|
TS-410B/U UHF Gener. |
|
|
|
TS-413C/U generator |
75 kHz to 40 MHz in six
bands, 11 tubes |
|
|
TS-418B/U
generator |
400 to 1000 MHz, 2C36
oscillator tube |
|
|
SG-24/TRM-3 sig. gen. |
AM-CW-FM sweep/marker
generator, 15 to 400 MHz in six bands. 35 tubes, incl. CRT. |
|
|
6-digit trochotron 1 MHz frequency
counter. |
|
|
|
URM-25 Sign Generator |
10 kHz up to 50 MHz in 8
bands. 9 tubes. |
|
|
Generator URM-26 |
4 to 405 MHz in 6 bands, 7
tubes |
|
Polarad |
Generator 1108AF |
6,85 to 11.00 GHz RF
generator; CW, FM or pulse modulation. A160034A klystron. |
|
Simpson |
479 Signal Generator |
AM marker, FM sweep
generator and crystal calibrator. |
Enter the Signal Generators and Frequency
Meters gallery
_________
Oscilloscopes
This section is almost
entirely devoted to Tektronix, the worldwide leader for this kind of
instrumentation through the sixties and the seventies. In those years almost
every electronic firm sold its own line of test equipment and of oscilloscopes
but in their advanced laboratories all used one or more Tek scopes as reference.
A Tektronix could cost more than a small flat or a Ferrari car: for this reason
I accepted the idea that I could just use these instruments at the University,
since I would never buy one. Tek scopes were very expensive, but they were
worth money paid for. Traces were sharp and bright, vertical amplifiers and
time bases were accurate enough to make possible a reliable evaluation of
observed waveforms and added features as the dual time-base, the intensifier or
the magnifier helped to catch every details. But the most outstanding features
of these instruments came from the accurate design of trigger circuits, able to
lock on any point of the input waveform at any frequency and with vertical
deflections of just few millimeters. Even the internal look was unique, with
the shining rows of passive components and of neon bulbs aligned between couple
of ceramic notched strips and with the tiny roll of silver loaded soldering
alloy, added somewhere inside for in-field emergency servicing.
Few oscilloscopes of other
sources are added to the Tek ones. The most relevant samples, for their
Tek-like complexity, were built by a small and smart US manufacturer now almost
forgotten, Lavoie Labs from Morganville, CT, founded by Steve Lavoie.
Remarkable are the mainframe LA-265A, equivalent to the Tektronix 545A, and the
plug-in vertical amplifier LA-265-CA, equivalent to the Tek CA plug-in. From
Lavoie Labs also a huge military set, second source of a HP rack oscilloscope
built to military specs.
|
Country / Mfr. |
Model |
Notes |
|
|
|
|
|
GB - Advance |
|
|
|
USA - Lavoie |
DC to 30 MHz, 12 ns
risetime, similar to Tek 545. |
|
|
|
LA-265-CA plug-in |
Vertical amplifier, similar
to Tek CA |
|
USA - Military |
OS-121D/USM-140 |
Plug-in dual-trace, made by
Lavoie |
|
USA - Simpson |
476 Mirroscope |
|
|
USA - Tektronix |
53/54C plug-in |
Dual trace amplifier,
forerunner of CA. |
|
|
81 |
Letter series plug-in
adapter for 585 |
|
|
82 |
Dual ch. plug-in for 585
mainframes |
|
|
|
|
|
|
453A |
8 x |
|
|
Dual-beam DC to 1 MHz,
100mV/cm. |
|
|
|
|
|
|
|
1 GHz direct view,
distributed deflection CRT, 47 tubes. |
|
|
|
531A |
15 MHz, single TB mainframe. |
|
|
Same as 531, dual TB. |
|
|
|
535A |
Same as 535, improved
bandwidth |
|
|
X-Y mainframe |
|
|
|
545A |
DC/30 MHz, dual TB |
|
|
547A |
DC/50 MHz |
|
|
DC to 100 MHz, dual TB |
|
|
|
Improved 585 |
Enter
the Oscilloscopes
gallery
_________
Tube
testers
In the sixties a tube tester
was an expensive oddity. Vacuum tubes were readily available and quite inexpensive,
at least the receiving ones. One could buy hundreds and hundreds of new tubes
for the same money asked for a simple emission tester. Heaters were readily
checked with an ohmeter. And at its best the tube tester could just return an
indication of a low-emission tube but did not help to return a radio or a
television set to its normal operation. On the contrary, simply replacing the
old tube with a new one, resulted not only in a more reliable indication but
even solved the faulty operation. Radio and television repair shops preferred
to have caddies or shelves with assorted spare tubes. Those wealthy people who
had bought a tube tester used it to screen all the discarded tubes for some
improbable future uses.
Tube testers gained popularity
when the production of vacuum tubes ceased. Old tubes, often pulled from
equipment withdrawn from service, could be returned to a new useful life, after
checking their relevant parameters on a tester.
I don’t like tube testers:
they are just useful to match tube pairs. The most accurate models are even the
most cumbersome to use, with the need of setting bias and load conditions for
each tube, in addition to the pin configuration and to the heater voltage. My
preferred types are the U.S. military I-177 or its updated version TV-7, simple
to use, fast and reliable.
The collection includes the
above types, the AVO MK4 characteristics meter and some Italian models.
|
Country / Mfr. |
Model |
Notes |
|
|
|
|
|
GB - AVO |
Valve Characteristic Meter
(VCM) MK
IV |
|
|
|
CT446 Test Set |
Military transistor tester |
|
Italy - Chinaglia |
PRV-410
tube tester |
|
|
|
Similar to PRV, plus
multimeter |
|
|
Italy - Unaohm |
Dynamic conductance about
1940 |
|
|
USA - Military |
I-177B
tube tester |
Dynamic conductance |
|
|
MX-949A/U |
Tube socket adapter kit |
|
|
TV-7 U
tube tester |
Updated I-177 |
|
|
|
|
|
USA Triplett |
3414 |
Emission tester |
Enter
the Tube testers gallery
__________
Multimeters,
VTVMs, DC Standards
This section includes several
kind of analog or digital voltmeters and multimeters, intended for measurements
of voltage, current or resistance values. These measurements were performed in
the past using analog meters, based upon some D’Arsonval type microammeters
with the addition of voltage dividers and of current shunts. The full scale
sensitivity of best meters was in the order of 50 microamps, resulting in an
internal resistance of 20 kohms per volt when used as voltmeters. Hence, if a
full scale value of 10 volts was selected to measure the control grid voltage
of a vacuum tube, the voltmeter internal resistance was in the order of 200
kohms: this value is found in parallel with the grid resistor and can
considerably alter the operating point of the tube. To measure these small
voltages vacuum tube voltmeters, VTVMs, were used. Here a vacuum tube
amplifier, usually connected in a balanced bridge circuit, grants very high
input impedance. Common values were 10 mohms for DC voltages and 1 mohm with
few picofarads for AC values.
The collection includes some
of the most appreciated multimeters, including two versions of the insuperable
AVOmeters. These were very accurate, with the moving coil on friction-free
taut-band suspensions, yet almost indestructible, with their patented overload
cutout. Until the late sixties AVOmeters, as well as other high-class
multimeters, were supplied with high-voltage ranges, 2500 volts AC or DC in
this case. Later, due to some stupid safety rules, maximum handling capability
was limited to 700 or 1000 volts.
Vacuum tube voltmeters include
the well known HP 410B and the RCA Senior Voltohmist, both fully restored.
Also available are some
different kind of electronic voltmeters, as true RMS digital voltmeters,
differential voltmeters, precision digital voltmeters and insulation meters.
This section is completed by
some voltage standards, based upon Weston cells.
Weston cells have been in use since 1905 as primary standards.
|
Country / Mfr. |
Model |
Notes |
|
|
|
|
|
Canada - Guildline |
Primary voltage reference,
12 Weston cells in a thermostatic oven. |
|
|
|
Primary voltage reference, 6
cells in a thermostatic oven w thermometer. |
|
|
GB - AVO |
AVOminor |
Pocket-size multimeter |
|
|
Universal multimeter,
various suffixes |
|
|
GB - Cropico |
Dual Weston cell |
|
|
GB - Megger |
BM80MIN/2 |
Insulation meter |
|
GB - Tinsley |
Dual Weston cell |
|
|
Italy - Geloso |
850 insulation meter |
|
|
Italy Microlambda |
Transistor Tester |
Microlamba Fusaro became
Selenia |
|
Italy - De Nigris |
FC15 frequency meter |
Reed frequency meter |
|
Italy - SAMAR |
SL200ED wattmeter |
Analog meter |
|
USA - Dana |
5 ¾ digit precision
multimeter |
|
|
USA - Eppley |
Weston cell |
|
|
USA Heathkit |
IM-11 VTVM |
|
|
|
IT-3120 transistor tstr |
|
|
USA - HP |
|
|
|
USA – Industrial Instruments |
RC1682 |
Conducivity bridge |
|
USA - Keithley |
660A
differential VM |
5-decade differential
voltmeter |
|
USA - Military |
TS-27/TSM Bridge |
|
|
|
TS-297/U |
Multimeter |
|
|
TS-352A/U |
Multimeter |
Enter
the Multimeters, VTVMs, DC Standards gallery
___________
AC measurements
This sub-section shows several
instruments used to measure AC or RF magnitudes. Here we find AC bridges,
vectorial voltmeters, but even some early X-band radar test sets from WWII.
Enter
the AC
measurements gallery
|
Country / Mfr. |
Model |
Notes |
|
|
|
|
|
Italy - Geloso |
421
capacitance meter |
Beat capacitance meter |
|
USA - Gen Rad |
Impedance bridge with
‘Orthonull’ |
|
|
USA - Fluke |
931B RMS voltmeter |
RMS differential voltmeter |
|
USA - Military |
X-band spectrum analyzer,
WWII |
|
|
USA – Technology Instruments
Co. |
Z-Angle Meter |
|
|
|
Z-Angle Meter |
|
|
|
|
|
|
|
|
|