MAGNAFON 24" BELVIS 2 YEAR 1976.

The MAGNAFON 24" BELVIS 2  is a 24 Inches B/W television with 8 programs preselection with sensor button program changer.
Each button contains even a lamp indicator of the program and tuning is performed with potentiometers in a drawbar box.
It has a  sensor keyboard for local commands, includes a plurality of tuning positions each defined by an adjustable potentiometer, a neon bulb indicator, a UHF/VHF switch and a two pole momentary contact touch switch. A common tuning capacitor has a tuning voltage developed thereacross for controlling the tuning of a varactor diode tuner. A source of reference potential is coupled across the tuning potentiometers and closure of any touch switch results in the tuning capacitor being charged from the voltage reference source through the selected one of the tuning potentiometers. The neon bulbs yield a visual indication of the selected tuning position. Circuitry for automatically placing control of the tuner to a preselected one of the tuning positions upon turn on of the receiver is also included. TV TOUCH-TUNING IC: With the developmente of application covering the use of m.o.s. devices for television and radio channel selection and indication a  device relates to a specially developed m.o.s.-technology integrated circuit which  is already produced in development quantities. The  touch -tuner as the i.c. is designated ans was  intended to replace mechanical push-button TV tuner mechanisms. It provides a sensing system which operates in conjunction with a finger -touch plate, a switching arrangement to control a varicap tuner and in addition outputs to operate channel indicating neon lamps. The sensing system comprises a very high -impedance circuit which is effectively shorted out by the resistance of a finger placed across the external touch plate. One side of the touch plate is connected to the sensing input of the i.c. and the other to a positive voltage which may be d.c. or a.c. When the touch plate is operated the channels are stepped through in sequence: the selected channel latches on and the appropriate indicator lights. The i.c. operates from a standard 33V varicap tuner supply and enables up to eight channels to be selected. Remote control can be applied to the system if required and the set is provided for that.

Touch sensitive control units form a welcome and natural adjunct to the use of varicap tuner units.
As they dispense completely with the need for electrical switches and switch contacts they should reduce further the number of service calls for tuning faults. Various circuit arrangements are used in touch operated tuner control units but all operate when a finger tip bridges a pair of contacts  which incidentally look at first glance like a single contact. When the finger tip completes the circuit forward bias is applied to a high gain switching transistor. This in turn switches on another transistor or transistors and the net outcome is that the supply to the appropriate tuning potentiometer is connected and held on while the supply to the previously selected potentiometer is switched off. In addition a channel ident fication bulb is usually brought into circuit. As skin resistance is high the touch contacts must be incorporated in a correspondingly high resistance circuit; in practice resistor values in the range 10-22MegaOhm are used. The switching operations are carried out either by discrete transistors or i.c.s. Transistors form almost ideal switches of course.


*** It has a Transistorized horizontal deflection circuits  made up of a horizontal switching or output transistor, a diode, one or more capacitors and a deflection winding. The output transistor, operating as a switch, is driven by a horizontal rate square wave signal and conducts during a portion of the horizontal trace interval. A diode, connected in parallel with the transistor, conducts during the remainder of the trace interval. A retrace capacitor and the deflection yoke winding are coupled in parallel across the transistor-diode combination. Energy is transferred into and out of the deflection winding via the diode and output transistor during the trace interval and via the retrace capacitor during the retrace interval.
In some television receivers, the collector of the horizontal output transistor is coupled to the B+ power supply through the primary windings of the high voltage transformer.

Has an unusual design form.


(Television set kindly donated to me by Marshal Elia Z.)

MAGNAFON RADIO TV was an Italian manufacturer of Radio and TV sets in Desio near Milan in Italy founded by Gino Magni, Now long extint !