This French-made tube tester was built around 1950. It is a so called pass/fail tester that does not measure entire the static curve, but only checks a few discrete operating points. The instrument is quite big and features almost all types of tube sockets available at the time on its front panel. The center display indicates the condition for a specific test measurement. The user connects the sockets pins to the required voltages using 10 big switches. A built-in paper drum shows the correct pin connections for a variety of common tubes and could be upgraded to include newer tubes.

The following measurements can be conducted:

  • heater (filament) continuity check
  • short-circuit check between various electrodes
  • cathode thermionic emission test
  • cathode-heater isolation (for indirectly heated cathodes)

Although this is a nice instrument, the partial information it provides can trigger false positives, or even worse, false negatives. Therefore, it is better to check the condition of a tube using a full-blown curve tracer (such as the venerable Tektronix 576 or 577).

The typed user manual is only in French.

The company Centrad was located in Rue de la Paix 2, Annecy, France. It is since long gone, but it seems that there is still some electricity-related shop at the location.

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

Circuit wise, this instrument is not much more than a custom transformer with multiple secondaries, alot of mechanical switches and tube sockets.

Centrad Lampemetre de Service Modèle 751

The paper drum with tube information.

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

 

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

The blue capacitor is a modern replacement for a dried out paper one.

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751

Centrad Lampemetre de Service Modèle 751