The vintage measurement tools
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.

Metrix 310

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.

Metrix U61

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 exotic devices.

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.

Ferisol CF201E

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 buy.

Tektronix 575

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.

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