The NUCLEAR / PLANET (PRANDONI) MOD. 2262 is a 12 inches B/W portable television with 8 programs keyboard tuning and potentiometers search system.
The use of voltage-variable diode-capacitors, such as varactor diodes, permits the electronic tuning of radio receivers and television receivers by the use of DC control voltages; so that the tuning elements no longer need to be intimately associated with the tuner. Thus, the tuned circuits of the tv receivers may be located remotely from the devices used to provide the necessary DC tuning voltages. In addition, the compact size of the voltage-variable diode-capacitor tuning circuits makes it desirable to use such tuning circuits in many tv applications which formerly used mechanically adjusted variable capacitors or the like as the tuning elements.
To employ voltage-variable diode capacitors in pushbutton tvs, however, especially in multiband pushbutton tv sets , a problem exists in providing a "memory," so that operation of a pushbutton will provide consistent tuning of the tv receiver to the station which is to be selected by that pushbutton. In addition it is necessary to provide some means for providing the initial tuning of the tv receiver for each pushbutton location in a manner which is reliable and inexpensive.
All commands are above located and the set allows both mains 220volt and 12volt supply types.
Recently, it has become more popular than ever to watch TV in a car as the number of cars increases. In general, a storage battery of 12 volts is used in small cars while one of 24 volts is used in large cars so that there is a disadvantage that a separate power supply device is required for driving a TV set in compliance with the respective battery used in the car. The present invention relates to a power supply circuit of a television receiver used in an automobile, and in particular to a power supply circuit of a television receiver which enables two different voltages from two kinds of supply respectively mains at 220v and dc 12v.
Was marketed with both brand names NUCLEAR and PLANET from PRANDONI Factory in 1979 and was first model with 8 programs tuning keyboard .
In the end of the 60's increasingly attention was focused on the varicap diode tuner as the latest, sophisticated means of television receiver frontend tuning in both colour and black and white sets.
The main purpose of this article is to investigate the servicing problems associated with this comparatively new method of tuning.
First however let's briefly recap on the principles involved in this tuning system:
The tuners use variable capacitance (or "varicap") diodes as the variable tuning elements: the effective capacitance of the diodes is controlled by the reverse bias applied across them, tuning being achieved by varying this voltage. As the reverse bias across a varicap diode is increased so its junction depletion region widens thus reducing its capacitance.
A VHF/ UHF television tuner is constructed in accordance with the present invention includes a preselector tuned circuit having a solid state voltage controlled capacitor as its tunable element, a radio frequency amplifier coupled to the preselector circuit and alsoother circuit to perfect the signal receiving capability and the application the like.
Considering the Mechanical Tuner Problems:
To get the servicing problems in perspective let us next consider the tuning arrangements previously used.
The earliest of these, employed on v.h.f., was the switched tuner which was either of the turret or incremental type.
The turret tuner substituted a coil bearing "biscuit" mounted on the rotating drum or turret when channels were changed. Twelve positions were normally provided, with a fine tuning knob to adjust the local oscillator frequency. As its name suggests the incremental tuner simply added more inductance to the tuned circuits at every downward channel movement: thus the highest inductance was present on channel one and the least on channel 12 (which normally covered 13 as well with manipulation of the fine tuner).
The movement towards u.h.f. TV working, initially with dual standard sets and later with single standard ones, brought about the need for u.h.f. tuners. In the earliest u.h.f. receivers valve tuners which were not particularly efficient were used.
The drive mechanism was usually a dual speed rotary system calibrated from channels 21 to 68. Experience in the field indicated that 625 line television was in many cases considered by the viewer to be inferior to 405 -line reception, on account of the poor signal to noise ratio achieved by the valve tuners. Many viewers were not prepared to use external u.h.f. aerials of course, having achieved satisfactory reception on v.h.f. with an indoor aerial: this aggravated the situation even more.
Another aspect which caused difficulty was the care needed to tune in a u.h.f. channel using a rotary tuner covering the whole of Bands IV and V. Many viewers simply could not tune in BBC 2 or ZDF or ORF or any channel correctly with such a tuning mechanism, finding that they had passed right over the channel they wanted before realising what they had done.
The advent of transistor tuners rapidly improved the quality of u.h.f. reception but use of a rotary mechanism was continued by many manufacturers. Thus while potential reception was improved the same tuning difficulties remained and viewers continued to gravitate towards 405 line viewing using the "old faithful" switched tuner. The operational breakthrough came with the introduction of the push-button u.h.f. channel change.
The mechanism is basically simple. Adjustable push buttons press down on a lever bar which in turn rotates the tuner's variable capacitors to the appropriate position. Each button is capable of tuning over the entire u.h.f. bands and this leads to customer confusion at times when after some adjustments which were too heavy handed they find themselves receiving ITV on a BBC button or a ORF and ZDF broadcasting or any channel possible !
Mechanical Faults:
Mechanical tuning obviously has its snags. There are for example contact springs which earth the tuning capacitor and go intermittent. This gives rise to the most random tuning defects, capable of driving the. most patient viewer to a state of total exasperation. It is also possible for the rotation mechanism to hang up and jam intermittently, or just become sticky, so that the reset accuracy of the mechanism is impaired and the receiver has to be retuned every time the channel is changed.
The vanes in the tuning capacitor can also short out at different settings, thereby eliminating some channels. The Varicap Tuner It will be seen then that mechanical defects can cause very irritating fault symptoms. If one thinks along the lines that anything mechanical is nasty, then the elimination of mechanical parts can only be to the good.
The logic of this is splendid provided the electronic replacement for the mechanical system is more reliable! Otherwise we are leaping out of the frying pan into the fire! In the light of experience gained with mechanical tuning devices it seems great that with the varicap tuner we have at last dispensed with the dreaded rotary tuning capacitor, replacing it instead with a variable voltage to the tuner.
Let us think about this however since things are never quite as simple as they first appear. The tuning voltage has to be variable in order to tune the receiver. Obviously then a means of varying the voltage has to be provided to act as the tuning control.
As it is a voltage that has to be varied the tuning control takes the form of a potentiometer., Now we have returned to a mechanical system again, though in a less complex form.
A potentiometer is required for each channel, selected by pressing the appropriate channel button.
We have lost a tuning capacitor and its rotating mechanism and gained a set of pots and selector switches therefore. Provided the pots and switches are mechanically more reliable than the tuning capacitor we should be better off-or should we?
Need for Voltage Stabilisation.
The voltage selected by the pots cannot be allowed to drift otherwise the receiver will go off -tune. The voltage supply to the potentiometers has to be stabilised therefore and a stabilising zener diode or integrated circuit (TAA550) .is needed for this purpose.
Any failure in this part of the circuit will give rise to tuning drift or worse, a total loss of reception. A short-circuit TAA550 for example will completely remove the tuning voltage while if it is open circuit the tuning can vary with picture brightness. Likewise any intermittency in the potentiometers or associated switching and/or resistors can also cause problems.
Relative Reliability of Tuners:
It will be seen then that in order to lose our troublesome mechanical arrangement we have had to introduce considerably more electronics which we trust are going to be more reliable. In addition we have not so far considered the relative reliability of the varicap tuner itself compared with the mechanical type. Since two r.f. transistors are generally used to compensate for the reduced Q of the varicap tuned circuits we immediately have twice the likelihood of an r.f. stage breaking down!
And being semiconductors the varicap diodes themselves are more likely to fail than the sections of a ganged tuning capacitor. It is reasonable then to conclude that if mechanical faults are the most prevalent the use of varicap tuners will make life easier. Mechanical faults are generally not too difficult to sort out however and the field engineer can often cope with them in the home.
Can the same be said of the varicap tuner? It seems that this type of tuner does not need so much attention as its mechanical counterpart but is likely to throw up some much more difficult faults when it does, resulting in bench repairs being needed. So far my own experience has indicated that varicap tuning faults nearly always need servicing on the bench.
Generally speaking it seems true to say that varicap tuners themselves are adequately reliable: the snags result from the tuning system and stabilised power supply.
Tuning Drift with Varicap Tuners:
If a varicap tuned receiver is constantly drifting off tune the +30V supply should be the number one suspect. It is best to connect an Avometer permanently to the supply so that it can be precisely monitored-if necessary write down the exact voltage measured.
If the receiver drifts, check the voltage. If it has changed, even slightly, this may well be enough to be the cause of the fault. To pinpoint and confirm the diagnosis aerosol freezer should be applied to the stabiliser i.c. or zener. If the voltage returns to normal or changes wildly for the worse the stabiliser is almost certainly the cause of the trouble and should be replaced.
A prolonged soak test should then be carried out. Another point concerning varicap tuners arises with their use in colour receivers.
There were makers of the most expensive colour receiver on the market still didn't use a varicap tuner but instead use a mechanical one. The makers' claim is that the signal to-noise ratio of the varicap tuner is inadequate for their colour standards. Undoubtedly the results obtained on the receiver seem to confirm this. Interestingly, the same manufacturers use varicap tuners in their black -and -white receivers, and the tuning button system is often full of troublesome intermittent contacts. The varicap tuner has its advantages and disadvantages then. Probably the simplest comment would be to say that when it is good it is very very good but when it is bad it is horrid!
TRANS CONTINENTS / OCEANIC / PRANDONI was an Italian manufacturer of radio and after of televison sets.
It was also the owner of brands like Trans Continents and Nuclear radio TV or simply Nuclear.
"Prandoni S.p.A." was founded by Dario Prandoni. Finally his son Giorgio Prandoni sold the company to the French "Thomson".
In 1998 Francesco Juilland and Giorgio Prandoni co-founded "Mediacube USA, Inc.", a film production company and a visual effects service provider in USA, Europe and in Italy.
a film production company and a visual effects service provider in USA, Europe and in Italy.
Giorgio Prandoni is a leading figure and heir to the most prestigious industrialist dynasty in the design and manufacture of radio equipment and multi standard television sets in Italy. (His father was Dario Prandoni the luminary owner of Prandoni S.p.A. one of Europe's most highly regarded electronic companies;
Dario
Prandoni formed the basis of the Prandoni Empire and Giorgio
Prandoni sells the company in France to Thomson with a big one deal).
During his tenure from 1998 to February 2002 as Mediacube's CEO
Francesco Juilland has created important joint venture between
Mediacube USA, Inc. and important European, American and Canadian
companies. He also brokered the acquisition of a share of Minerva
Pictures (Italy) they own a library of more than 1,500 titles of
which 850 are for worldwide rights in perpetuity. The titles include
classics works by Pasolini, Germi, Bellocchio, Godard, Fellini,
Antonioni and others. Most recently in 2000, Francesco Juilland was
elected in the Board of Directors of Ionic WW Studios, a fully
digital Hollywood studio organized and financed by Mediacube as Major
Investor together with Giorgio Prandoni and Javier Rodriguez,
Spanish businessman and scion of an important and conservative Family
of Spain full of history and tradition and thank to the greenlight
of a guardian angel like the economist Mr. Diego Colombo, chairman
of the Colombo Group with offices in Switzerland and around the
world and longtime serious advisor of the Juilland family office.
Francesco Juilland is in the Board of Directors with the man that he
considers his American mentor Mike Medavoy (producer, former
chairman of Tristar Pictures and a legendary "Hollywood industry
hero" as Fox News channel calls him, many times Oscars winner, his
movies including the masterpieces Apocalypse Now, Philadelphia,
Dance with wolves, Who flew over the Cuckoo's nest, Annie Hall,
Platoon, Rocky, the Sting, Silence of the lambs, Amadeus, The
Terminator, Sleepless in Seattle) and Norman Pattiz (called from
"USA Today" and "LA Times" The Ted Turner of the radio) and Arnold
Messer (president of Phoenix Pictures, company producer of Larry
Flint, The thin red line, U-Turn, The 6th Day, Basic, Holes, Stealth,
All the King's men), together with David Hayden and Gigi Pritzker
(film producer with Deborah del Prete of "the Wedding Planner" with
Jennifer Lopez)Further Readings and Notes
^ Radiogrammofono PDRS 9 (PDF), in Selezione Radio, Anno I, nº 2, Febbraio 1950.
^ Brevetto per marchio d'impresa nr. 05875 del 1 febbraio 1952.
^ Baiocato, NRC 333 Radio Nuclear Radio Corporation; Cassano D'Adda MI,, su www.radiomuseum.org. URL consultato il 16 febbraio 2018.
^ Carlo Grimaldi, Tutto a transitors (PDF), in Informazione industriale, 1967.
^ Guidi, Stereo-Matic Hi-Fi 75 R-Player Prandoni SPA; TREVIGLIO BG, b, su www.radiomuseum.org. URL consultato il 16 febbraio 2018.
^ La Prandoni ritorna in attivo (PDF), in Selezione di tecnica Radio TV, Settembre 1982, p. 6.
^ Brevetto per marchio d'impresa nr. 05875 del 1 febbraio 1952.
^ Baiocato, NRC 333 Radio Nuclear Radio Corporation; Cassano D'Adda MI,, su www.radiomuseum.org. URL consultato il 16 febbraio 2018.
^ Carlo Grimaldi, Tutto a transitors (PDF), in Informazione industriale, 1967.
^ Guidi, Stereo-Matic Hi-Fi 75 R-Player Prandoni SPA; TREVIGLIO BG, b, su www.radiomuseum.org. URL consultato il 16 febbraio 2018.
^ La Prandoni ritorna in attivo (PDF), in Selezione di tecnica Radio TV, Settembre 1982, p. 6.
External links for further information
- Alcune pubblicità degli anni 40-50
- Informazione industriale del 1967
- Fondo Prandoni in Lombardia Beni Culturali
- Principali apparati Prandoni
