Portable TV Elektronika VL 100 is intended for reception of television programs, both at home and on the street, outside of town, in the car on a retractable telescopic antenna. The CRT has a screen diagonal size of 16 cm and a deflection of the electron beam at an angle of 70°. The TV is from the network of alternating current with voltage 127/220 V or DC 12 V. In TV is designed with jacks for connecting lead-in cable external antenna, headphones, tape and extra bass amplifier. Technical characteristics of the TV are compiled in table. 1.
Table 2
The size of the image
H mm
Horizontal resolution
450 lines
The sensitivity of the channels of image and sound
100 µv
The adjacent channels is not worse
26 dB
Nominal sound power
150 MW
Power consumption from the battery
5 W
The size of the TV
HH mm
Weight (without AC adapter)
2.8 kg
The television shown in Fig. 1
At the entrance of the TV set 12-channel upgraded unit PTC-P. It differs from what is described in "Radio", 1966, No. 1, page 21, of the block of PTC-P switching circuit of the transistor gain stages of HF. Governing the AGC voltage is supplied to the base of the transistor of the cascade, and with the increase of the signal at the input of the TV shifts its operating point in the direction of saturation.
The TV used is relatively simple and easily adjustable three-stage if amplifier image on which input is enabled patienterna filter centered selection (FSS). The first and second stages of the amplifier inverter collected on the transistors T1,T2, loaded single contours, have a wide bandwidth and covered by the ARU. Riccia carrier FC sound (31,5 MHz) is carried out using the contour L10C15 in the circuit of the base of the transistor T3.
The third amplifier stage (transistor T3) loaded bandpass filter L11C18, L12C21 with external capacitive coupling through the capacitor C19. This filter, together with the FSS provides the necessary selectivity and the frequency response shape.
Neutralization of internal feedback transistors in the first two stages is carried out by the supply voltage connection with coils L7 and L9 at the base of the transistors T1i and T2 through capacitors C7 and C11. The neutralization voltage in the third cascade is removed from the resistor R20 and is supplied to the base of transistor T3 via a capacitor C16.
The if amplifier has a maximum gain of about 70 dB. The selected scheme provides a sufficiently wide bandwidth and satisfactory phase characteristic.
The video detector of the television is built on the diode D1 according to the standard scheme. The load detector is a resistor R22. At the output of the video detector installed U-shaped filter STS. Choke this filter is intended to simultaneously adjust the frequency characteristics of the amplifier.
From the video detector signal goes to the first stage amplifier, assembled on the transistor T4, the emitter follower for matching the high output impedance of the video detector with a low input impedance amplifier.
Between the first and second stages of the amplifier included rejector circuit L13С25, tuned to a frequency of 6.5 MHz, which removed the sound signals to the if amplifier. The second cascade amplifier is performed on the transistor T5, connected in the circuit with common emitter and complex correction of the frequency response. With amplifier signals of positive polarity are fed to the cathode of a CRT device ARU and the selector node synchronization. Direct link DC between the load detector and the cathode of the kinescope provides transmission of a constant component of the video signal. Adjusting the contrast of the image is performed by changing the voltage of the video signal at the cathode of the kinescope via potentiometer R35. Distortion frequency characteristics that appear with this method of adjusting the contrast, are compensated by means of capacitors C30 and C31. The amplifier has a gain of at least 70 bandwidth of 4.75-5 MHz.
The device ARU contains two stages: key stage transistor T6 and the DC amplifier transistor T7. To the base of transistor T6 is supplied a negative voltage to the delay of 5-6 V. It will open only if the signal level is taken from the amplifier exceeds the threshold delay, and at the same time to the collector of this transistor goes positive flyback pulses from the output to the output of the transformer horizontal, coincident in frequency and phase with the sync pulses. The transistor T7 of the DC amplifier connected in the circuit with common emitter. It is attached to the key stage through the two-tier filter C35 R45 and C36 R47, which determines time constant of AGC. When no signal or low signal, the transistor T7 is closed and does not cause voltage variations, and hence the current in the circuit AGC. When a signal goes above the threshold delay this transistor, and T6, is opened and the output of the cascade appears positive control voltage AGC.
Channel sound TV consists of two resonance cascades of sound if amplifier transistors T8 and T9 included in the common-emitter circuit, a frequency detector against the diodes D2, D3 and low frequency amplifier transistors T10-T12.
To obtain the maximum gain of the inverter load circuits L15C40 and L17C43 included in the collector circuit of the transistors T8, T9 fully. Resistors R49, R53, R56, R58 are used to prevent self-excitation of the if amplifier. Detector relationship is built on a symmetrical pattern. Such a detector is the easiest to configure and better suppress spurious amplitude modulation. Amplifier WOOFER has no peculiar features. Its output power is 150 MW. It is loaded with two speakers 0,GD.
Node synchronization consists of three stages: the amplitude selector (transistor T21), bass reflex (T22) and a buffer amplifier human clock (T13). With amplitude selector lowercase sync after differentiation comes in patinvert, the outputs of which are highlighted lowercase pulses of both polarities with amplitude of about 5 V. These pulses are received AHR and f collected through the diodes D4, D5. Human synchronizing pulses are separated from the lower case in two-tier integrates the filter R101С62, R100C61 and amplified in the buffer stage. With the release of this cascade carries the sync signal in negative polarity is received at the master oscillator frame scanning.
The node line scan consists of three stages: oscillator transistor T23, the preliminary stage of amplification (T24) and output stage (T25). Specifies the horizontal-sweep generator is the scheme of the blocking oscillator with emitter-base connection. This generator has a high input impedance, which is needed for normal of the AFC and F. Sawtooth pulses are removed from the point of connection of the load resistors R113 and R114 in the collector circuit of the transistor T23. Through this connection to the generator of the preliminary stage of amplification excludes the effect of changing the input impedance on the operation of the blocking oscillator. Duration prooobably pulses is largely determined by the resistances of resistors R11, R113 and R114. From the last two depends on the frequency of the pulses.
The preliminary stage of amplification of the line scanning unit (T24) operates in key mode and performs the functions of the power amplifier. The transistor T24 has a conductivity opposite the conductivity of the transistor T23. During the forward stroke of the sweep this transistor is closed. He opens with pulses of positive polarity supplied from the blocking oscillator. Further through a matching transformer TP4 pulse signal with no DC component is supplied to the base of transistor T25 output stage line scan. This cascade operates in the two-way key and loaded output flyback transformer, directly connected to the lower coils of the deflection system. For passing the DC component of the collector current of the transistor T25 is connected to the power source through the winding of the flyback transformer.
During the forward stroke horizontal transistor T25 is in saturation and is able to pass through output flyback transformer TP5 and deflecting lowercase coil high current. At the beginning of the return stroke to the base of transistor through a matching transformer is fed a positive rectangular pulse with a fast leading edge, which quickly locks the transistor. A positive voltage pulse arising in linear transformer during the return stroke of the beam, is used to obtain the voltage of the second anode of the picture tube (9 kV) accelerating and focusing electrodes (500), the filament voltage of the tube (1.35 V), the power transistor T5 (80 in) and other auxiliary voltages. As the damper is used, the diode D6.
The node frame scanning is performed by a transformerless circuit. The master oscillator is assembled on the transistors T14, T15, T16 scheme multivibrator emitter connection. In this cascade is implemented by the combination of the generator linearly varying voltage with nonlinear resistance (transistor T16), and a relaxation oscillator, the transistors T14 and T15). The amplitude of the sawtooth voltage at the output of the master oscillator is almost equal to the supply voltage.
As the output stage vertical sweep applied push-pull power amplifier of class "b" on the two composite transistors (T17-T19 and T18-T20). Characteristic for class "D" non-linear distortion such as "step" eliminated by adjusting the bias voltage at the bases of the transistors.
The TV Elektronika VL-100" from AC current through the stabilized rectifier with an output voltage of +10.5 V relative to the housing of the TV. Remote network unit consists of a small power transformer (TP6), rectifier bridge (d - D) and filter capacitor (s). To stabilize the size of the raster and the parameters of the TV when operating from a DC voltage generator or vehicle voltage stabilizer constructively placed directly in the housing of the TV. He performed on the transistor T26 (cascade control), T27 (cascade pass) and the reference diode d13. The stabilizer through the divider R131-R134 from special rectifier DC is supplied a negative voltage - 50, produced in the line scanning unit. This voltage sets the operating mode to the regulating transistor T26. The stabilizer feature is the dependence of the mode of operation of the pass transistor T27 from voltage - 50 in coming to the base of transistor T26. This protects the transistor T25, the output stage line scan, and the transistor T27 from breakdown. The regulator maintains a constant output voltage of the rectifier when changing mains voltage within ±10%. It has a ripple less than 100 mV. In the rectifier circuit pads provided for charging 12-volt portable rechargeable battery. The battery can be charged while watching television.
Structurally, the TV Elektronika VL 100" consists of several functional blocks. Two main circuit Board - Board receivers and the payment of scans arranged vertically on both sides of the picture tube, and a third charge with the auxiliary rectifiers and the power of the PTC-P - top. All three boards hinged and attached to the frame by hinges. The TV has easily removable metal case, when removing which offers access to the entire installation. On the upper wall of the case is reinforced handle with built-in telescopic swivel antenna. The screen of a CRT occupies the entire area of the front panel. Speakers 0,GD located on the bottom of the TV in horn speaker.
Wrap-contour data of the coils of the TV are compiled in table. 2, and transformers - in table. 3.
Table 2
Designation scheme
The number of turns
The wire: mark and dia, Fox
L1
25
PELSHO 0,2
L2
10
"
L3
15
"
L4
35
"
L5
25
"
L6
15
"
L7
5
"
L8
15
"
L9
5
"
L10
35
"
L11
20
PELSHO 0,35
L12
20
"
L13
15
PELSHO 0.2
L14
10
"
L15
31
"
L16
6
"
L17
35
PELSHO 0.1
L18
H
LASO 7x0.07
L19
15
PELSHO 0.1
L20
650
Sew 0,13
All coils are wound on frames with a diameter of 6 mm in a single layer (excluding L20) round (L17 and L19 on one frame, L18 - two wire), and set up podstroechnye cores SB-12A (th-1A), except for L20, which is applied to the ferrite core type CNF-13.
Table 3
Designation
Core
NN conclusions
The number of turns
The wire: brand & diameter, mm
TP1
Permalloy 45N Sh
1-2
3-4
4-5
2100
290
290
Sew-1 0,06
Sew-1 0,06
Sew-1 0.06
TP2
The same
1-2
3-4
4-5
450
450
80
Sew-1 0,09
Sew-1 0,09
Sew-1 0,23
TP3
Occifer MNM type B
1-2
3-4
500
100
Sew-1 0,08
Sew-1 0,08
TP4
The same
1-2
3-4
250
50
Sew-1 0,08
Sew-1 0,23
TP5
Occifer MNM ø 7x7
1-3
3-2
2-6
6-4
4-5
5-7
25
5
10
36
600
2700
Sew-2 0,15
Sew-2 0,35
Sew-2 0,35
Sew-2 0,35
Sew-2 0,05
Sew-2 0,05
TP6
Steel SL 3310 12X20
1-2
2-3
4-5
1607
1160
175
Sew-1 0,22
Sew-1 0,15
Sew-1 0,64
DR1
Occifer MNM type B
120
Sew-2 0,12
DP2
Ferrite NN length 40 mm, diameter 4 mm (RLS-70)
60
Sew-2 0,23
Authors: L. Kissin, G. Sadovskaya, V. Uteshev; Publication: N. Bolshakov, rf.atnn.ru