analogue multimeter – Goerz Minitest

Goerz Minitest
Goerz Minitest

The Goerz multimeter, model: Minitest FE5101 dates from 1969 and was manufactured by the company Goerz Elektro Ges.m.b.H from Vienna.

Introductory sentence from the operating instructions: “It is a multi-measuring instrument, which is particularly suitable for service work in the field of news and radio technology and electronics due to its small dimensions and low weight as a pocket instrument It allows the measurement of: equal and AC voltages, DC and AC, resistance, capacitance and frequency. “

The internal resistance is 20kOhm for DC and 4kOhm for AC. The achieved accuracy is 2.5%

inside view

As overload protection, the moving-coil meter is equipped with antiparallel-connected diodes.

In this model, the measuring ranges are not to be selected by a selector switch, but each individual measuring range is designed as a socket on the device. The sockets themselves are suitable for 2mm banana plugs. The power supply for the resistance measurement comes from a 3V dry cell battery (type 2R10 duplex battery).



For the measurement of the capacitance with this device an external voltage is necessary, because here no own alternating voltage generator is installed. This said external voltage is the 50 Hz mains voltage which is connected to the device via its own supply cable. So a capacity measurement up to 500nF can be achieved. Measurements greater than 0.5uF are no longer possible due to the low measuring frequency. Goerz supplied a polystyrene transport case for storage and transport.    Sende Artikel als PDF   

analogue multimeter – Unigor 3n

Unigor 3n
Unigor 3n

From the years from 1964 comes the analogue multimeter Unigor 3n from Norma, respectively Goerz-Metrawatt. It was characterized by the large measuring range of 52 measuring ranges, all of which can be selected with just one selector switch. The measuring mode and polarity reversal is realized with a push-button switch. All measurements (except the 10A range) are possible on just one terminal pair.

The measuring mechanism is a “clamping band measuring unit” with a very good vibration resistance and low self-consumption.

The internal resistance for voltage measurements is a maximum of 4MOhm in the highest measuring range (see photo technical data). The voltage drop in current measurements is given as 12mV in the 120uA range and 120mV in the 30A range. The measuring accuracy is 1% for DC and 1.5% for AC measuring ranges.

Like the Unigor 6e, the 3n model is also equipped with various safety features.

The power supply of the multimeter takes over a 1.5V mono cell.


Technische Daten
technical specification    Sende Artikel als PDF   

The steam engine

Wilesco steamengine

The following piece is about 40 years old model steam engine from the manufacturer Wilesco. (Thanks to Manfred for the loan for the media preparation). The model consists of a highly polished and nickel-plated brass kettle, which is built into an old copper-colored boiler house with brick pattern. Heating is done with a dry spirit burner located under the boiler. The pressure vessel has a spring safety valve and a “Domdampfpfeife”. The pressure line is led to a single-acting pendulum cylinder, which in turn drives the crank and the flywheel on it via a connecting rod.Trockenspiritusbrenner.

IMAG0064The entire model is mounted on an iron plate. In order to be able to drive mechanical models with the machine, a pulley is mounted on the shaft of the flywheel. Since the model has been stored in a carton for the past forty years, a few small jobs have been done. Piston and crank were stiff and had to be cleaned and re-oiled. The crank was a bit out of alignment with the flywheel shaft.

IMAG0057The seals of the “Domdampfpfeife” and the pressure relief valve were also brittle and hardened and were replaced. Here I was able to use a suitable punching tool made of “new” old gasket material to knock out and insert two new gaskets. Now the model was a little bit freed from the dust of the last years and cleaned and a start attempt was nothing in the way.

Now the spirit burner could be filled with a small piece of dry spirit, which was probably even older than the machine itself. At least the original box looks like this:

IMAG0054 IMAG0055


Invalid Displayed Gallery

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science kits PHILIPS EE 2000 series


Another electronics kit from my youth is the Philips EE series. It dates approximately to the years 1976-1979. The box presented here is the EE2050. Unfortunately, this is no longer the original that I recorded back then, but a version bought on eBay. But this is a real collector’s item, because the box has never been recorded.

The boxes (EE2003 / 41/50/51/52) under my custody have unfortunately not survived the years. Since the modular system was designed in such a way that all components were “free”, ie not riveted to any sockets (just as they were also used in industry), I always used them. If I needed a resistor or capacitor quickly, the kit had to serve as a “donor”.

Befestigung des Bauteils auf der Grundplatte
Fixing the component on the base plate

The concept of the modular system: It consists of a perforated plastic base plate through which a hairpin spring is inserted. This hairpin spring in turn holds a spiral spring. Now, between the hairpin spring and the upper end of the coil spring, the connection wire of the component can be clamped.

Transistor on printed circuit board

The components themselves are contained in the box as they are also commercially available. An exception here are only the transistors and transformers. They are mounted on a small printed circuit board, which facilitates assembly and also protects the component itself from mechanical stress.

In the final stage, the box consists of two bolted base plates, which in turn are bolted to a control panel. In this media console then turn capacitors, rotary potentiometers, buttons, bulbs and a speaker place. The number of experiments to build is also huge. The manuals are very well structured. They describe the basics of DC technology, as well as the operation of the circuits.

Here is an excerpt from the inscription of the electronics box. Note the gender-oriented spelling 🙂


Wonderful world of electronics – a mysterious world that every boy wants to get to know and understand. This electronic kit gives him the opportunity to easily gather his own insights in this field. The box contains a richly illustrated instruction book and over 150 items – e.g. 10 resistors, 5 capacitors, photocell and transistors. Thanks to the clamping system, the young electronics builder can assemble these parts completely independently and without prior knowledge to the following functional devices:

Burglar Alarm Systems, Amplifiers, Automatic Parking Lights, Humidity Indicators, Acoustic Relays, Morse Exercise Machines, Brightness Controls, Timers, Others – a total of 21 electronic devices and many interesting circuits.

With additional boxes the possibilities extend to the MW radio with loudspeaker. Proper engineers work with the same parts: all the boxes in the Philips Elektronik series are equipped with the most modern parts of today’s electronics in their original form.


IMG_3778IMG_3777IMG_3776IMG_3784    Sende Artikel als PDF   

Multimeter analog

Unigor 6e (ca. 1970)

A good friend of the older generation of technicians is certainly the analog multimeter of the manufacturer Unigor. In this case, it is the model Unigor_6e from the 70s.

An excerpt from the preface of the operating manual:

The electronic instrument Unigor 6e combines the advantages of classical measuring technology with those of modern electronics.

It was specially developed for measurements in the field of electronics and for all those applications where practically no power is required. The high sensitivity is achieved by means of a battery-powered transistor amplifier.

The field effect transistor chopper for DC measurements and the multiple negative feedback guarantee high stability and negligible drift. The large measuring range and the high accuracy of 1% at AC and DC, allows universal use in the radio and television service in test field and laboratories.

The “6e” offers a total

  • 54 DC and AC / voltage ranges
  • 13 dB ranges
  • 12 resistance and capacity ranges
  • 2 temperature ranges
measuring ranges

The electronic components of the meter are powered by four 1.5V batteries and take a current of about 2.5mA. The working range of the electronics is between 4V and 7V. The battery is switched on with the rotary switch (which also represents the R, C adjustment knob at the same time). To check the battery voltage, a check position is provided on the measuring range shutter.

The Unigor 6e also offers a variety of protective devices and is therefore protected against damage caused by incorrect handling and overload. (I can remember quite well from my school time that this is not always the case: D)

The Unigor 6e has an electromechanical circuit breaker function. Its relay responds to overloads with DC and AC and requires no auxiliary power. The protection therefore remains fully effective even when the battery switch or battery is switched off. The restarting in case of permanent overload is prevented by a special switching mechanism.

Furthermore, fuses provide protection at the higher current ranges to respond in the event of a short circuit or tripping of the circuit breaker.

Against overvoltages at the inputs are voltage arresters at the input terminals whose breakdown voltage is lower than that of the internal circuit.

Scale sheet of the Unigor 6e    Sende Artikel als PDF   

The flame licker


A small mechanics project occupied me this time. It is again about a hot air engine. This time not about the Stirling engine, but the so-called “flame eater”.

During the search in the World Wide Web, I found, among other things, the website of Mr. James Maiwald. Mr. Maiwald is an ambitious modeler and specialist in the field of Stirling and vacuum engines. He develops and manufactures his own models in all variants and also offers them as a kit.

More precisely, it is a vacuum motor, which is popularly also called a flame eater. He is one of the hot air engines, but unlike the Stirling engine is an open system.

Technically speaking, it is an atmospheric engine, since here the external air pressure does the work (comparable to the first gasoline engine). As a result, the maximum piston force is limited to the product of piston area and air pressure. (Wikipedia)

Detail view slide valve

And exactly one such model (lying the flame eater) is here. As I assemble the engine and the first time commissioning is seen in the following short video …

More information and interesting models and kits can be found on the website of Mr. Maiwald:    Sende Artikel als PDF   

Radioreceiver in retro look – The finishing

The wooden case is painted

Now that the front panel is milled, it can be cleaned and the engravings are provided with black paint. After the varnish has dried in the indentations of the engraving, the supernatant paint is removed with solvent. Now the entire panel could be painted with clear lacquer.

While the paintwork on the front panel is drying, it’s time again for the wooden cabinet. The mounting holes for the boards, speakers, etc. were drilled and then the wood was embedded with a slightly darker wood stain. After drying, the wooden case also gets a clear coat.

In the next step, the operating elements (switches and rotary encoders) and the LC display are attached to the front panel. The milled webs for the speaker panel are covered with black fabric. (For the fabric had to serve a T-shirt).



The painting of the housing dried about a day. Now you can start mounting the speakers and the board.

Installation of the speakers


Die Platine wird mit Abstandhaltern am Gehäuseboden verschraubt.

Assembly of the board


Now a suitable power supply is missing. For this purpose, a small power supply was built, which consists only of an iron core transformer with subsequent rectification, smoothing and voltage stabilization with a LM7809, ie 9V DC. For this, a small board was made (about 5x8cm) and also built into the housing with spacers.

Power supply 240V AC to 9V DC at max. 350mA


Now that everything is assembled, the amplifier metrics and levels are again set and optimized with signal generator and oscilloscope.



The finished radio receiver now looks like this from the front …

Radio from the front


und die Geräterückseite ist im nächsten Bild dargestellt:


In the short video, the radio can be seen in operation:    Sende Artikel als PDF   

TEDDY automatic

IMAG1321From the years 1970-1972 the radio receiver TEDDY AUTOMATIC 100 comes from the German manufacturer ITT – Schaub Lorenz. It is a multi-band receiver that covers the wave ranges of long wave, short wave, medium wave and ultrashortwave.

It is designed for mains and battery voltage (110-127V / 220-240V and for battery operation for 4×1.5 volt size AA cells).


The output power is 0.8 watts and is transmitted with a dynamic oval speaker.

The technical structure according to the manufacturer consists of 6AM circles and 9FM circles. The receiver principle is a SUPERHET with ZF 460kHz and 10.7MHz. The housing is made of plastic (thermoplastic) and has the dimensions of 215x127x70 mm with a weight of 1.2kg.


Connection for external sources
Switch for receiving frequency    Sende Artikel als PDF   

torsion pendulum clock

A patience-related work is the restoration or repair of a rotary pendulum clock.

A rotary pendulum clock is, as the name implies, a mechanical clock that generates the clock from a pendulum rotating around its own axis. The vibration energy is transmitted here with a torsion spring (Horolovar spring), ie a very fine steel wire special alloy. IMAG1268_1 The rotary pendulum clock is also called annual clock, as due to the very slow oscillation and corresponding mechanical implementation of the escapement, a lift of the spring accumulator only once in 300-400 days is necessary.

Of course, this also requires a certain precision of the mechanical components. If something is not set correctly here, the clock will switch off after a few minutes. Even the fine adjustment of the accuracy requires some patience. And just like a clock has done to me. In an online auction house, I have a cheap ‘defective’ but purchased from the components ago complete rotary pendulum clock and immediately started to disassemble and clean the parts.

Knurled screw for the pendulum diameter


suspension spring

After this work we went back to the assembly. The Horolovar feather was replaced by a new one. Now we went to the adjustments. First, I had to find out how many pendulum oscillations, more precisely half vibrations, should make the clock in one minute. At my watch (a Kundo) these are eight beats. The easiest way is to use a stopwatch to measure the time it takes to reach the 8th half-cycle. For example, if the measured time is over one minute, the watch will run too slowly and must be adjusted with the thumbscrew (the one that changes the position of the pendulum weights in diameter). Turning the thumbscrew clockwise will make the clock slower and counterclockwise faster, of course.

Hemmung mit Ankerplatte
Escapement with anchor plate

It should be a precision of +/- 1 minute per month possible. So a deviation of 12 minutes a year. Of course this requires optimal environmental conditions. (constant temperature and humidity, as well as a firm, vibration-free state)
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Surrounded by radioactivity?

After the self-made Geiger Müller counter and the associated experiments, I noticed that there is one or the other radioactive element in our environment.

With the SOEKS 01M Geiger counter, an industrially manufactured device, I have now again “scanned” objects in the area.


Again, I realized that some of the old clocks in my collection are equipped with radium-painted dials. The SOEKS shows here a radiation exposure of about 1.11 microSievert per hour. The environmental load is displayed at approx. 0.14 uSv / h.IMAG1290

But in my mother’s kitchen, I found a beautiful, colorful old vase that displayed about 10uSv / h. (The thing is now in the far corner of the cellar).

It should be uranium paint. (To see orange / red painting in the video below)    Sende Artikel als PDF