FUNKE TUBE TESTER MODEL W 19

Since for the short test a sensitive meter of 1000 ohm/volt is used even small insulation leakage is shown,

Amplifier tubes are checked with DC from the built-in power supply: it contains a high-vacuum full-wave rectifier which, in connection with a large filter condenser supplies a ripple-free DC. This feature is important since in tubes with several grids the shape of AC ripple may affect the indication.

Rectifier tubes are measured with AC from the built-in heavy transformer. The AC voltages used for this purpose are fixed at for instance 10V~, 30V~, 60V~ 100 Volt~ etc. and the right voltage is connected with the tube by the test card automatically.

In order to measure the amplifier tube two spots of the tube characteristic are measured, one with the bias of 0 volt and the other with the bias of -2 volt. The grids are connected with the DC power supply, the filament is fed with AC, just as it happens in the normal use of the tube, thus this measurement means a test of the gain.

The indication of the meter is interpreted by the reading of the test card, it gives the tolerances between which the tube is „Gut“ that is „good“, or „Noch brauchbar“ that is „weak“, or „Unbrauchbar“ that is „Bad“ (for foreign tubes the sign „?“ is used instead of „weak“ just as is usual in the country of origin of the tube).

W 19 is not a plain „Emission-Tester“ but it really tests the tube performance. It is not designed in the way the cheap testers are where all grids and the plate are connected with each other and a low voltage, sometimes even only AC, between filament or cathode on one hand and all the other electrodes on the other hand gives a reading of something which has no meaning at all because it has nothing to do with the data of the tube or with its characteristic, This only gives an emission test but is no measurement while the Funke Tube fester really measures two values of the characteristic, as mentioned before.

Twin tubes or other tubes with two or more complete systems, for instance a triode and hexode, are measured twice automatically, first one system and then the other.

During the measurement the tube doesn’t need to be removed from the tube socket and put into another socket but remains in the one into which it has been put originally. That is true for tubes with one system as well as for tubes with two or even three systems.