Some measurement tools are needed to carry out test on
amplifiers : oscilloscope, LF generator and multimeter (analog
or digital). Here are some useful devices that can be used in the
lab. If testing or matching tubes are needed, the lampmeter become
indispensable. To supply a project, a prototype or to test an amp
wich has a blown power transformer, a high voltage supply is useful.
The fans of the " vintage " measure will turn to the curve
tracers, high voltage Wheatstone bridges, etc.
A very common lampmeter in the amateur radio circle, the
310 is not yet considered as a measurement tool because none
of its supplies are regulated. To avoid too much dispersion
in measurements, Metrix have equipped it with a calibration
system based on mains biasing. Tubes are tested in AC mode,
allowing a large cathode flow of current, without
overheating the tube.
The 310 exists in different releases (B, D, CTR, CTRM),
the differences are on the sockets, finishing, and the
environnement in wich it is used.
High quality, definitive design and rock solid reliable:
40 years on the 310 performs like new.
Called the " Tube analyser ", The U61 is a
complete and luxurious test bench. The parameters of the
tube under test are simultaneously measured with five
galvanometers. All DC supplies are regulated ,
connectors allow external measurement tools to be attached.
The U61 produces a plate current of 100mA at 300V. Metrix
designed the 661, an extension of the U61, with electronic
cicuitry designed to measure the tubes dynamic slope. This
model, is rare and unefficient, but it has the charm of the
Built until 1975, the U61, became LX109 in its last
release was equipped with modern galvanometers, a white
front panel and extra plugs to automate the selection of
tubes. Still expensive today, despite its age, the U61 is
the benchmark of lampmeters.
French brand, created in 1950, well known for its
generators, Ferisol built few measurement devices then
disappeared in 1974, bought up by Schlumberger and Oritel.
Designed for tubes assemblies, the power supply delivers
6,3VAC/8A and 0 to 300VDC/100mA. This variable output is
regulated by a quartet of EL84. The galvanometer indicates
different output voltage or current settings. A specific
jack allows the connection of several CF201 in parallel or
series. Highly compact with good performance, it is a great
The 575 Tektronix is a transistor caracteristics curve
tracer. It's pleasant to talk a bit about this device,
undispensable when doing an analysis on a transistor amplifier.
The 575 allows the measurement in dynamic mode of lots
characteristics, two of which are the gain current and the
max collector/emitter voltage. This two last parameters are
important when searching an equivalent or analysing a
doubtful transistor. A double socket and a switch allows a
qwick match of all bipolar transistor.
This magnificent device was designed as part of the 500
series, during the Tektronix " golden age ", where
no solution was too expensive. It still does the job today.