NORDMENDE SPECTRA PORTABLE COLOR 4201 YEAR 1979.

The NORDMENDE SPECTRA PORTABLE COLOR 4201 is a 17 inches portable color television with 8 programs preselection keyboard, program number display and potentiometric search tuning system.
The mechanical turret approach to television tuning has been used almost exclusively for the past 60 years. Even though replete with the inherent disadvantages of mechanical complexity, unreliability and cost, such apparatus has been technically capable of performing its intended function and as a result the consumer has had to bear the burdens associated with the device. However, with the " recent " Broadcast demands for parity of tuning for UHF and VHF channels, the increasing number of UHF and cable TV stations have imposed new tuning performance requirements which severely tax the capability of the mechanical turret tuner. Consequently, attempts are now being made to provide all electronic tuning to meet the new requirements.

The invention relates to a tuning unit with bandswitch for high frequency receivers, especially radio and television receivers, having a potentiometer system for the control of capacity diodes, the said potentiometer system consisting of a plurality of parallel resistance paths along which wiper contacts can be driven by means of screw spindles disposed adjacent one another in a common insulating material housing in which a bandswitch formed of metal rods is associated with each tuning spindle.

In these tuning units, the working voltages of the capacity diodes in the tuning circuits are recorded once a precise tuning to the desired frequency has been performed. A potentiometer tuning system has great advantages over the formerly used channel selectors operating with mechanically adjustable capacitors (tuning condensers) or mechanically adjustable inductances (variometers), mainly because it is not required to have such great precision in its tuning mechanism.

Tuning units with bandswitches formed of variable resistances and combined with interlocking pushbuttons controlling the supply of recorded working voltages to capacity diodes are known. Channel selection is accomplished by depressing the knobs, and the tuning or fine tuning are performed by turning the knobs. The resistances serving as voltage dividers in these tuning units are combined into a component unit such that they are in the form of a ladderlike pattern on a common insulating plate forming the cover of the housing in which the tuning spindles and wiper contacts corresponding to the variable resistances are housed. The number of resistances corresponds to the number of channels or frequencies which are to be recorded. The wiper contact picks up a voltage which, when applied to the capacity diodes determines their capacitance and hence the frequency of the corresponding oscillating circuit. The adjustment of the wipers is performed by turning the tuning spindle coupled to the tuning knob. By the depression of a button the electrical connection between a contact rod and a tuning spindle is brought about and thus the selected voltage is applied to the capacity diodes. Since the push buttons release one another, it is possible simply by depressing another button to tune to a different receiving frequency or a different channel, as the case may be.

 Moreover, using this arrangement, the only indication--during adjustment--of which channel is selected is by station identification.

Was the first type of models series color screen really portable from German NORDMENDE factory.

The chassis is a modular type like bigger model but horizontal deflection is based with:

- Horizontal Beam Deflection  and high voltage generating circuits realized with Thyristors circuits.

The massive demand for colour television receivers in Europe/Germany in the 70's  brought about an influx of sets from the continent. Many of these use the thin -neck (29mm) type of 110° shadowmask tube and the Philips 20AX CRT Tube, plus the already Delta Gun CRT . 

Scanning of these tubes is accomplished by means of a toroidally wound deflection yoke (conventional 90° and thick -neck 110° tubes operate with saddle -wound deflection coils). The inductance of a toroidal yoke is very much less than that of a saddle -wound yoke, thus higher scan currents are required. The deflection current necessary for the line scan is about 12A peak -to -peak. This could be provided by a transistor line output stage but a current step-up transformer, which is bulky and both difficult and costly to manufacture, would be required. 

An entirely different approach, pioneered by RCA in America and developed by them and by ITT (SEL) in Germany, is the thyristor line output stage. In this system the scanning current is provided via two thyristors and two switching diodes which due to their characteristics can supply the deflection yoke without a step-up transformer (a small transformer is still required to obtain the input voltage pulse for the e.h.t. tripler). The purpose of this article is to explain the basic operation of such circuits. The thyristor line output circuit offers high reliability since all switching occurs at zero current level. C.R.T. flashovers, which can produce high current surges (up to 60A), have no detrimental effects on the switching diodes or thyristors since the forward voltage drop across these devices is small and the duration of the current pulses short. If a surge limiting resistor is pro- vided in the tube's final anode circuit the peak voltages produced by flashovers seldom exceed the normal repetitive circuit voltages by more than 50-100V. This is well within the device ratings.  It's a very good system to use where the line scan coils require large peak currents with only a moderate flyback voltage  an intrinsic characteristic of toroidally wound deflection coils. The basic thyristor line output stage arrangement used in all these chassis is shown in Fig. 1
it was originally devised by RCA. Many sets fitted with 110°, narrow -neck delta -gun tubes used a thyristor line output stage - for example those in the Grundig and Saba ranges and the Finlux Peacock , Indesit, Siemens, Salora, Metz, Nordmende, Blaupunkt, ITT, Seleco, REX, Mivar, Emerson, Brionvega, Loewe, Galaxi, Stern, Zanussi, Wega, Philco. The circuit continued to find favour in earlier chassis designed for use with in -line gun tubes, examples being found in the Grundig and Korting ranges - also,  Indesit, Siemens, Salora, Metz, Nordmende, Blaupunkt, ITT, Seleco, REX, Mivar, Emerson, Brionvega, Loewe, Galaxi, Stern, Zanussi, Wega, Philco the Rediffusion Mk. III chassis. Deflection currents of up to 13A peak -to -peak are commonly encountered with 110° tubes, with a flyback voltage of only some 600V peak  to peak. The total energy requirement is of the order of 6mJ, which is 50 per cent higher than modern 110° tubes of the 30AX and S4 variety with their saddle -wound line scan coils.   The only problem with this type of circuit is the large amount of energy that shuttles back and forth at line frequency. This places a heavy stress on certain components. Circuit losses produce quite high temperatures, which are concentrated at certain points, in particular the commutating combi coil. This leads to deterioration of the soldered joints around the coil, a common cause of failure. This can have a cumulative effect, a high resistance joint increasing the local heating until the joint becomes well and truly dry -a classic symptom with some Grundig / Emerson sets. The wound components themselves can be a source of trouble, due to losses - particularly the combi coil and the regulating transductor. Later chassis are less prone to this sort of thing, partly because of the use of later generation, higher efficiency yokes but mainly due to more generous and better design of the wound components. The ideal dielectric for use in the tuning capacitors is polypropylene (either metalised or film). It's a truly won- derful dielectric - very stable, with very small losses, and capable of operation at high frequencies and elevated temperatures. It's also nowadays reasonably inexpensive. Unfortunately many earlier chassis of this type used polyester capacitors, and it's no surprise that they were inclined to give up. When replacing the tuning capacitors in a thyristor line output stage it's essential to use polypropylene types -a good range of axial components with values ranging from 0.001µF to 047µF is available from RS Components, enabling even non-standard values to be made up from an appropriate combination. Using polypropylene capacitors in place of polyester ones will not only ensure capacitor reliability but will also lower the stress on other components by reducing the circuit losses (and hence power consumption).
       Numerous circuit designs for completely transistorized television receivers either have been incorporated in commercially available receivers or have been described in detail in various technical publications. One of the most troublesome areas in such transistor receivers, from the point of View of reliability and economy, lies in the horizontal deflection circuits.
       As an attempt to avoid the voltage and current limitations of transistor deflection circuits, a number of circuits have been proposed utilizing the silicon controlled rectifier (SCR), a semiconductor device capable of handling substantially higher currents and voltages than transistors.
       The circuit utilizes two bi-directionally conductive switching means which serve respectively as trace and commutating switches. Particularly, each of the switching means comprises the parallel combination of a silicon controlled rectifier (SCR) and a diode. The commutating switch is triggered on shortly before the desired beginning of retrace and, in conjunction with a resonant commutating circuit having an inductor and two capacitors, serves to turn off the trace switch to initiate retrace. The commutating circuit is also arranged to turn oft the commutating SCR before the end of retrace. 

Such kind of application was uncommon for small screen fromats.

Was even first model of NORDMENDE production with a TOSHIBA BLACKSTRIPE CRT TUBE.

All other commands are manually regulated on front right.

An upside locate antenna is provided.

The set is build with a Modular chassis design because as modern television receivers become more complex the problem of repairing the receiver becomes more difficult. As the number of components used in the television receiver increases the susceptibility to breakdown increases and it becomes more difficult to replace defective components as they are more closely spaced. The problem has become even more complicated with the increasing number of color television receivers in use. A color television receiver has a larger number of circuits of a higher degree of complexity than the black and white receiver and further a more highly trained serviceman is required to properly service the color television receiver.
Fortunately for the service problem to date, most failures occur in the vacuum tubes used in the television receivers. A faulty or inoperative vacuum tube is relatively easy to find and replace. However, where the television receiver malfunction is caused by the failure of other components, such as resistors, capacitors or inductors, it is harder to isolate the defective component and a higher degree of skill on the part of the serviceman is required.
Even with the great majority of the color television receiver malfunctions being of the "easy to find and repair" type proper servicing of color sets has been difficult to obtain due to the shortage of trained serviceman.
At the present time advances in the state of the semiconductor art have led to the increasing use of transistors in color television receivers. The receiver described in this application has only two tubes, the picture tube and the high voltage rectifier tube, all the other active components in the receiver being semiconductors.
One important characteristic of a semiconductor device is its extreme reliability in comparison with the vacuum tube. The number of transistor and integrated circuit failures in the television receiver will be very low in comparison with the failures of other components, the reverse of what is true in present day color television receivers. Thus most failures in future television receivers will be of the hard to service type and will require more highly qualified servicemen.
The primary symptoms of a television receiver malfunction are shown on the picture tube of the television receiver while the components causing the malfunction are located within the cabinet. Also many adjustments to the receiver require the serviceman to observe the screen. Thus the serviceman must use unsatisfactory mirror arrangements to remove the electronic chassis from the cabinet, usually a very difficult task. Further many components are "buried" in a maze of circuitry and other components so that they are difficult to remove and replace without damage to other components in the receiver.
Repairing a modern color television receiver often requires that the receiver be removed from the home and carried to a repair shop where it may remain for many weeks. This is an expensive undertaking since most receivers are bulky and heavy enough to require at least two persons to carry them. Further, two trips must be made to the home, one to pick up the receiver and one to deliver it. For these reasons, the cost of maintaining the color television receiver in operating condition often exceeds the initial cost of the receiver and is an important factor in determining whether a receiver will be purchased.
Therefore, the object of this invention is to provide a transistorized color television receiver in which the main electronic chassis is easily accessible for maintenance and adjustment. Another object of this invention is to provide a transistorized color television receiver in which the electronic circuits are divided into a plurality of modules with the modules easily removable for service and maintenance. The main electronic chassis is slidably mounted within the cabinet so that it may be withdrawn, in the same manner as a drawer, to expose the electronic circuitry therein for maintenance and adjustment from the rear closure panel after easy removal. Another aspect is the capability to be serviced at eventually the home of the owner.

(To see the Internal Chassis Just click on Older Post Button on bottom page, that's simple !)


Nordmende was a manufacturer of entertainment electronics based in Bremen, Germany.
The original company, Radio H. Mende & Co, was founded in 1923 by Otto Hermann Mende (1885-1940) in Dresden. Following the destruction of the plant during the bombing raids in 1945, Martin Mende (the founder's son) created a new company in Bremen in 1947, in a former Focke-Wulf plant, under the name North German Mende Broadcast GmbH. The name was subsequently changed to Nordmende: subsequently the company became one of the prominent German manufacturers of radios, televisions, tape recorders and record players in the 1950s and 1960s.

In the 1970s, Nordmende televisions were renowned for their innovative chassis, and for the rigorous testing and quality control of their finished products. Both created high costs, however, which soon proved a competitive disadvantage when the price of colour televisions began to plunge.

In 1969, Mende's sons took over the company, and in 1977 a majority shareholding was sold to the French Thomson Brandt company and the chassis remains the original NordMende until CHASSIS F9. The following year, the family sold their remaining shares to Thomson. In the 1980s, the factories in Bremen were closed, Nordmende becoming purely a Thomson trademark (Starting from chassis F10 F11 they're all THOMSON).








In the 1990s, the name Nordmende was used with decreasing frequency, and it eventually disappeared in favour of the Thomson name. In 2005 Videocon Group acquired all cathode ray tube activities from Thomson. This led to the creation of VDC Technologies, which manufactures TV sets using the Nordmende brand under licence from Thomson.
The Nordmende brand name was relaunched in Ireland in September 2008 by the KAL Group. Although Nordmende was well known for its televisions throughout Ireland during the 1970s and 1980s, the company bought the rights to the name and launched a range of white goods including fridges, freezers, washing machines, and dishwashers, alongside a revamped range of flat-screen TVs and stereos.

     
NORDMENDE HISTORY IN GERMAN:

Die Vorkriegsgeschichte findet sich unter Mende. Nach dem Totalverlust in Dresden gründet Martin Mende (30.12.1898-1982) unter Mitwirkung von Hermann Weber am 26. August 1947 [FT5901] in Bremen-Hemelingen die Norddeutsche Mende-Rundfunk GmbH.

Die ersten Gehäuse liefert ein Tischler in Achim gegen Kompensation von fünf Gehäusen zu einem Rundfunkgerät. Der frühere Mende-Konstrukteur, Obering. Heer zeichnet wieder für die Geräte verantwortlich [FT49??].

Ab 27. Juli 1948 liefert die neue, zuerst 18 und bald 60 Personen umfassende Firma auf Grund von Währungsreform, Krediten und Zulieferverträgen die neue Radioproduktion.

Das Regime in Ostdeutschland lässt den Namen Mende nicht zu, so dass Martin Mende mit grafischen Konstruktionen im Zusammenhang mit «Nord» an seinen Vorkriegserfolg anschliesst.

Die Hallen der ehemaligen Focke-Wulf AG beim Bahnhof Seebaldsbrück dienen als Werkstätten. 1950 beschäftigt das Unternehmen 700, 1959 schon 3500 und im Zenit 6300 Personen.

1950 beginnt die Firma mit UKW-, 1953 mit Fernseh- und 1954 mit Mess- und Prüfgeräten. Gegen Ende der 50er Jahre heisst die Firma Norddeutsche Mende Rundfunk KG [RP7901].

Nachdem sich Nordmende bislang nicht mit Magnettongeräten befasst hat, bringt das Werk 1958 das erste deutsche Heim-Tonbandgerät mit drei Motoren auf den Markt. Allerdings dominieren auf diesem Sektor eindeutig andere Firmen wie AEG/Telefunken und Grundig. Von Nordmende kommen jeweils nur ein bis zwei Geräte (1960 keines) in die Kataloge. Dafür hat die Firma Erfolg mit einem anderen Neueinstieg:


1958 stellt Nordmende mit «Mambo» ihr erstes Reisegerät vor - aber nicht «das erste deutsche, serienmässig hergestellte und volltransistorisierte Koffergerät», wie man aus einer Quelle nachlesen kann. Danach wird Nordmende in Deutschland auf dem Sektor Reisegeräte besonders stark, obwohl sie keine Röhren-Koffer baute. Immerhin kosten die in «Mambo» verwendeten 8 Halbleiter dann im Einzelhandel DM 98.70, während für die vier D-Röhren der 90er-Serie - auch zum Katalogpreis - etwa DM 35.- auszugeben wären. Preis des ganzen Gerätes: DM 189.- plus zwei Flachbatterien von 4,5 V.

Bis 1969 gibt es ca. 92 Modelle der tragbaren Radios (Koffer- bzw. «Handradios», d.h. «Hand held radios»). Beispielsweise finden sich im Katalog 1961/62 [448] je 11 Tischradios und Radiomöbel sowie 8 Modelle von Reiseradios. 17 verschiedene Fernsehmodelle zeigen dagegen, wo in jener Zeit der Erfolg zu holen war.

Gemäss [FT7901] liegt Nordmende während kurzer Zeit mit der sogenannten «Tippomatik-Bedienung» sogar technisch vorne. Siehe auch Philips etc.

Auch Konzertschränke scheinen Ende der 50er bis Anfang 60er Jahre eine tragende Säule für Nordmende zu sein. Dabei verwendet die Firma immer wieder gleiche Namen wie «Cabinet», «Caruso», «Casino», «Cosima» sowie «Arabella» und «Isobella» mit wechselnden Zusatz-Nummern oder den Zusatz «Stereo», z.B. in den Jahren 1959 und 1960/61.

Im März 1967 nimmt das Werk die Produktion von Farbfernsehgeräten auf. Zum Firmenjubiläum erscheint eine Gerätereihe mit der Bezeichnung 'Goldene 20'. 1969 übernehmen die Mende-Söhne Karl und Hermann die Geschäftsführung.

1977 führt der verschärfte Wettbewerb zum Verkauf der Mehrheit an den französischen Konzern Thomson-Brandt; die Familie Mende zieht sich anschliessend ganz aus dem Unternehmen zurück. Martin Mende stirbt 1982.

R.I.P.  GERMANY.............

Weblinks:

 Commons: Nordmende – Sammlung von Bildern, Videos und Audiodateien
Tote Marke NORDMENDE – Verblasster Stolz. Artikel im Manager-Magazin
Ein neues Programm. Artikel in der Zeit
Fernseher: Inder produzieren neue Nordmende. Artikel bei itespresso.de
Videocon produziert Plasmaschirme für Nordmende. Artikel im pressetext.de

Einzelnachweise

Spectra Color Studio und Spectra SK2 Color de Luxe Studio auf radiomuseum.org
Marke Nordmende mit Digital- und Internetradios zurück, teltarif.de, Artikel vom 2. September 2017.


Company profile. Phillar, archiviert vom Original am 6. März 2008; abgerufen am 26. April 2013 (englisch).


Broschüre – Sprachmanager24. Abgerufen am 5. Januar 2015.