Presentation of Model 1
This small tube tester was provided in the 1960s
with the Radio course of the company EURELEC. This
type of course and devices were better known in Germany under
the name EURATELE and ELETTRA in Italy.
It was coupled with a multimeter set to the 1mA DC range.
The 1mA measuring part of the controller is shown schematically further on.
This type of tube tester could not compete with professional models. It only allowed assessing the emission capability of a tube's cathode and possible short circuits in the grids. No measurement of slope and other characteristics ...
This type of tube tester could not compete with professional models. It only allowed assessing the emission capability of a tube's cathode and possible short circuits in the grids. No measurement of slope and other characteristics ...
For a given tube, the Eurelec guide gives 3 adjustment points:
- The filament heating voltage
- The wiring configuration in diode mode
- The adjustment of anode current (emission tests)
Dial and simplified schematic of the EURELEC multimeter
On the 1mA DC range, the equivalent schematic of the controller is shown below.
The maximum deflection, in direct current, is obtained when it is traversed with an intensity of 1mA.
Its internal resistance is 72Ω. The voltage across its terminals is then 72mV.
Electrical schematic of the tube tester
Example of use
Eurelec recommended the following connections for testing tubes not listed in the provided guide:
A: corresponds to the positive high voltage and B: ground (0V), then
use a GOOD tube as a reference for the Emission Test potentiometer.
| Cathode | Grid1 | Grid2 | Grid3 | Anode | |
| Diode | B | — | — | — | A |
| Triode | B | B | — | — | A |
| Tetrode | B | B | A | — | A |
| Pentode | B | B | A | B | A |
Operating principle
In the case of an EF93 pentode, the guide gives:
To facilitate reading the schematic when the pentode and the controller are
connected, a synthetic diagram is given below. It shows
the operating principle of this tube tester. An alternating voltage is applied
between the cathode and anode of the tube operating here as a rectifier.
The peak anode voltage
is 71V. Voltage measurements across R1 and R2 allow
determining the peak currents (and average by dividing by \(\pi\)).
When the
This type of multimeter, when traversed by a half-wave rectified sinusoidal current, displays a value close to this average value. It seems that the manufacturer gives an emission potentiometer position at 75% deflection for the nominal characteristic. The small measurement/calculation discrepancies are probably due to the precision of the resistors.
When the
EMISSION TESTpotentiometer is in the 64% position, this means that a resistance of 44Ω is in parallel with the multimeter + 100Ω assembly.
This type of multimeter, when traversed by a half-wave rectified sinusoidal current, displays a value close to this average value. It seems that the manufacturer gives an emission potentiometer position at 75% deflection for the nominal characteristic. The small measurement/calculation discrepancies are probably due to the precision of the resistors.
Guide to the combinations of the EURELEC tester
| Tube | Socket | Heat. | C1 |
| C2 | C3 | C4 | C5 | C6 | C7 |
| C8 | C9 | CAP | Page | EMIS. |
Subject to errors contained in the guide provided by Eurelec
Thanks to Michel Marignan for the extensive work of digitizing the Eurelec courses.
Thanks to Michel Marignan for the extensive work of digitizing the Eurelec courses.
Adapter for another galvanometer
If the multimeter described above is not available, an adapter can be inserted between the Eurelec tube tester and a more common galvanometer.
An example is given for an adaptation to a Monacor 100µA / 1K moving coil. This coil deflects to its maximum for a voltage of 0.1V across its terminals.
To adapt this setup to your spare parts or your multimeter, simply adapt \(R_2\) using the following relation knowing the sensitivity \(V_S\) of the moving coil or the multimeter (in volts) $$V_S = I_1.R_2 \Rightarrow R_2=1000.V_s$$ To ensure compatibility with the Eurelec controller, R1 must always be equal to \(72\Omega\).
For a graduation from 0 to 100, here are the reading zones:
To adapt this setup to your spare parts or your multimeter, simply adapt \(R_2\) using the following relation knowing the sensitivity \(V_S\) of the moving coil or the multimeter (in volts) $$V_S = I_1.R_2 \Rightarrow R_2=1000.V_s$$ To ensure compatibility with the Eurelec controller, R1 must always be equal to \(72\Omega\).
For a graduation from 0 to 100, here are the reading zones:
- 0 to 42: BAD
- 42 to 58: ? (PASSABLE)
- 58 to 100: GOOD
An example of an implementation based on a low-voltage supply OpAmp is given opposite. The specification of the OpAmp is available here
ICL-7611
Sources and references
[1] The user guide for the Eurelec tube tester - Eurelec.net and Jean-Marie HUBIN (304Mo)
