Category Archives: Retro technique

Technology mainly in the field of consumer electronics, audio and video technology. Repairs and device presentations

Calculator from 1975: PICO PA-80N

From 1975 this Japanese calculator comes. He was sold from 1975 to 1976 by the Eduscho – Tchibo coffee chain. The device is called “PICO” PA-80N. Exactly this model was also once in my father’s possession and I was already fascinated by the luminous seven-segment displays as a child. And that was the problem again. As far as I can remember, I was in elementary school age, when I first disassembled the device into its individual parts. That was not the problem, but it was not there. Over time, I disassembled the computer several times. At some point wires broke off and nothing worked. Reassembled, the Pico then disappeared into a box and was disposed of years later by my father. Why I took apart and assembled the small computer again and again, I can not say today anymore. Apparently it was the success of an eight-year-old, after assembly again to have a working device – just to last. 🙂 On an online flea market platform, I found just such a calculator and in addition to that in a TOP condition and almost gave it. So I had to have him …

Pico with the imitation leather case
To the dates:
The display has eight 7-segment digits based on LED technology. To be able to read the MikroLEDs they are embedded in a convex shaped plastic. This achieves a magnifying effect that makes the numbers readable.
Siebensegment – Anzeige mit 8 Digits

LEDs under the convex plastic encapsulant
The housing is made of aluminum and plastic and has the dimensions in about a cigarette box. 8.2 x 5.7 x 2.4 cm. In order to keep the calculator gently, there was a leatherette case to do so.
Mainboard des PICO

The calculator is powered by two Tripple A (AAA) batteries, so with 3V. Optionally, there was also an external power supply that could be purchased according to the then price list by almost 18DM. (unfortunately no price information for Austria)

Power adapter socket at the top
Technically, the small computer consists of a display board, a “motherboard” and a keyboard board. These boards are connected to each other with a multipolar bridge line. This should not be bent too often, because then quickly break off individual wires …
Opened circuit boards
The display board is driven by a Toshiba T1337 Displaydriver IC and the computer itself is a GI C593 (General Instruments) processor that handles the basic operations and percentage calculation. The processor works with a supply voltage of 15-17VDC and is able to drive Floureszentplays directly. In order to produce in the small Pico computer from the 3V of the AAA batteries also the 17VDC a small DC / DC converter on the Mainboard expires.
central processing unit
DC / DC converter circuit for the 17V of the CPU
datasheet from theC593 (source: 1977 Datacatalog GI Microelectronics)
In addition to the faux leather case, there was also a card with a user manual and a flyer. It was printed with warranty information and an advertising slogan:
“The Pico will become an indispensable arithmetic assistant for you. At school, at home, at work – wherever there is something to be expected, the Pico is at your fingertips. Just press keys, and you’ve already calculated the most complicated tasks. This is how arithmetic becomes a pleasure! “(Source: Internet)
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Philips “Sonate” Philetta Euro280

Philips Philetta Euro 280 “Sonate”

In the years 1968 to 1970, the radio receiver was built with the inscription “Philetta Euro 280” by Philips. It is a small multi-band receiver with transistor equipment. The type designation 12RB280 / 30 with the inscription “Sonata” seems to be another version of this model. In any case, I have dug up the version “Sonata” – once again from the depths of the Kellergefilde – and after superficial cleaning connected to the mains. Immediately after switching on, the scale illumination lights up and a loud 50 Hz hum can be heard from the loudspeaker. Increasing the volume level adds some noise. So switched to the FM band and searched for a station – and lo and behold, it works. Only the buzzing disturbs. Otherwise, the device works without any major problems. To find the cause of the humming, you begin with the troubleshooting as usual in the power supply.

entfernte Rückwand

The rear panel is quickly removed and the power supply unit, consisting of a, mounted on a support plate transformer including rectifier and filter capacitors removed. Now, without using the oscilloscope and the multimeter, you can immediately see where the ravages of time have left their mark. The two electrolytic capacitors do not look quite healthy anymore.

A quick measurement of the voltages brings certainty. The DC voltages have a decent ripple, which causes the “hum”. So the function of the electrolytic capacitors to smooth the DC voltage is no longer, or poorly, given. A measurement of the capacities confirmed that. So I renewed the capacitors.

Power supply with renewed capacitors

Immediately after switching on, even before I had the probe at the measuring points, a noise was heard without “humming”. The oscilloscope image now showed a clean DC voltage – almost no ripple. The receiver worked again very clean, without disturbing background noise. That was apparently the only mistake.

Technical information:

The main principle of the receiver is a superhet (according to the superposition principle) with an IF of 460/10700 kHz. The waveband of the receiver:

frequency scale
  • long wave
  • medium wave 1 (520-1400kHz)
  • medium wave 2 (1400-1600kHz)
  • shortwave
  • UKW

The output stage has a power of 3W, which is converted into sound energy in a dynamic loudspeaker with permanent magnetic excitation. The case is made of plastic and has the dimensions 43×17.5×10.5cm with a weight of 2.4kg. The receiver is supplied with 220V / 50Hz mains voltage.



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Walkman City Bummler from the 80s

IMG_3810From the early 1980s comes the “City Bummler” a mobile, portable cassette player – in short a Walkman. At that time, I received it as a Christmas present during my middle school years. The special feature of this device was a built-in microphone and two headphone ports. So you could listen to music in pairs and if you wanted to say something without having to remove the headphones (or to reduce the volume), so you had to press only  an orange colored button and the intercom was active. The device was sold as a low-priced “replica” version of the first Walkman from Sony, the TPS-L2 which came on July 1, 1979 on the market. The citybummler was distributed by UNIVERSUM via the source mailer.

City Bummler with a self made coverplate after the original got broken

The device was delivered in a box with headphones, cassette pocket and carrying case with strap. For operation, three AA size 1.5V batteries were needed. The volume control is carried out with two separate sliders, so that each channel can be controlled separately. Unfortunately, the city loafer has not passed the last 35 years quite unscathed. Over time, the cassette cover was broken off, which I then replaced in my youth with a homemade tinplate lid. At some point I did not like the case color and I painted the device green. (or I just had green paint at hand). At least the “loafer” still exists and it works too.

IMG_3814I was then on the Web in search of a well-preserved, in the original state city loafer. However, the offer is extremely low and the few offers on online auction houses are not interesting because of the immense shipping costs.

Fellow FE-1

But a compromise and at the same time a new piece in the collection is the FELLOW FE-1 Walkman. I got the most cheap and fully functional on a second-hand stock market.

left: Fellow FE-1, right: City-Bummler
both devices in comparison

The Fellow is also a clone of the Sony TPS-L2. It differs essentially in the arrangement of the keys of the drive.






IMG_3811IMG_3809IMG_3808IMG_3821 IMG_3812 IMG_3814 IMG_3819


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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.

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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



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Minerva Tempocord

Minerva Tempocord

A multi-band radio receiver from the year 1957 is the Tempocord of the company Minerva. The company Minerva was founded in Vienna in 1919 and began in 1924 with the production of radio receivers. The radios were initially made under the name Radiola or Aeriola. It was not until 1926 that the receivers were built under the name Minerva. The name Minerva was used until 1972.

The device here refuses any service after being supplied with the mains voltage. Thus, a first error is found quickly. The mains voltage does not reach the transformer. The reason for this is the mains fuses, which protect the transformer from all poles. Here are both broken. Probably because the transformer tap was clamped to 220V … Rectification and smoothing capacitors are fine.
a look inside the paperfuse
paper fuse
The fuses, however, are wrapped in paper security wires, which are wrapped at the ends each with a brass clip. Due to the lack of availability of these old fuses, the fuse holders located on the Trafoprint have been swapped for current ones and reinserted. After carefully raising the supply voltage, the receiver was again able to elicit sounds …

Technical Data:

  • Manufacturer brand: Minerva-Radio Wien
  • Model:  Tempocord
  • Construction year: 1960
  • Typ: Radio receiver (postwar receiver)
  • tubes: ECC85 ECH81 EF89 EBF89 EM81 EABC80 EL84 EZ80
  • Operating principle / construction: Superhet receiver IF 480/10700 kHz
  • 2 NF stages . 11 FM circles and 6 AM circles
  • wavebands: longwave, medium-wave, shortwave and ultrashortwave
  • Supplyvoltage: 110V, 130V, 150V, 220V,  240Volt
  • Speaker: dynamic permanentmagnet-ovalspeaker
  • Wooden housing with dimensions: (BxHxT)55 x 32 x 25 cm

(sources: wikipedia)

IMAG0040 IMAG0041

(the device was provided for documentation purposes by: Berti)

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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


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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



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F101 Voodoo Radarmonitor

From a McDonnel F101 Voodoo came the following sample that I got from a customer back then, with a request to try to bring it back to life somehow.
The thing I’m writing about was a black cylinder about 30 centimeters long and about 20 centimeters across. On one end face of the cylinder was a picture surface as seen from an oscilloscope, with a rotatable scale ring with a 0 to 360 degrees angle label.
The customer told me it was the cockpit radar of a Starfighter jet. Then I began to research what turned out to be relatively expensive at that time, in the mid-90s, especially since the Internet did not yet exist in the form and diversity as it exists today.

picsource: Wikipedia

But at least I found out that the part was really the board monitor of the radar system of an airplane. Namely to the radar monitor of a McDonnel F101.
A twin-engine fighter aircraft of the 50s cold war US Air Force.
In any case, the part came from this plane – wherever the customer had it from. And he asked me if I had any chance of getting it up and running. He meant that he wanted to see the famous, rotating light stroke on the screen.
At that time, I could not find any information or documentation on the part, how to connect the tangle of cables over cables, which came out of the device …

frontview of the monitor

So I started dismantling. Several miniature electron tubes, transformers and many smaller tubes with bobbins with immersion cores and many, many capacitors were installed. In the longitudinal axis of the device, the picture tube was housed, with the magnetic deflection was rotatably mounted about the axis of the tube. Say, the complete deflection unit was turned around the tube by means of an electric motor drive.


Since I had no chance to somehow understand the circuit, especially since apparently some components, such as the entire voltage and signal conditioning were not integrated in the monitor, but apparently were installed elsewhere in the plane, so I set out to dismantle everything. All that was left was the picture tube with the mechanics and the deflection coils and the drive. On a breadboard I started to make my own drive for the coil drive. For the deflection coil itself, I built a sawtooth generator with a sufficiently strong power output stage. And for the high voltage of the tube had to serve an old line transformer of a television, which was driven by a NE555 (the old known timer module) and a matching power transistor (some BU508 …).

and it´s turning again

The whole circuit was operated at about 24V and took over 2A. (including cathode heater and electric motor and the scale bulbs that illuminated the labels).
But it worked. On the screen was a green line, which turned at the adjustable rotational speed. That was already everything. There was no beam modulation or the like to draw any simulated radar images. Today you could work together with small microcontrollers like Arduino and co, quite simply …

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The 80s and the Watchman

In 1985, the company Sony brings a small, compact and above all mobile TV on the market. The Watchman Voyager FD20-AEB. It has been designed to be used everywhere. For example, in the car, on vacation, just everywhere.
It is not a TV with LC display, or TFT, or LED display. No. The TV brings the image by means of a cathode ray tube (Braun tube) to the eye of the beholder. And not in the brilliant color variety and resolution of today’s receivers, but in black and white (BW).



The screen diagonal of 4.7 cm can be displayed with the help of a clip-on magnifier still a little enlarged.
The receiver is a multinorm receiver that covered the European television standards.

It was tuned manually by means of a side-mounted “rotary wheel”. The reception tapes VHF / UHF can be selected with a slide switch. Of course, only analog TV reception is possible.

source drawing: Frank’s



Settings such as brightness, contrast and also the image capture can be carried out on the underside of the device.

 Tunermodule and flattube

The power supply comes from four 1.5 volt AA batteries or from a power supply. At a power consumption of 2 watts is relatively fast on battery operation. The high voltage generation and heating of the flat screen tube is probably one of the biggest consumers of electricity.

The structure of the boards is very discreet. There are hardly any integrated circuits. The large tuner module can be seen on the left in the picture. The supply of signals takes place exclusively via a telescopic rod antenna. A built-in speaker provides the sound. Optionally, a jack for connecting a headphone is installed.

today there is only more noise to be received
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