CONTENTS Parts Information Switches and Relays Basic Theory of Video Systems NTSC and PAL TV Systems Measuring Instrument Pattern Generator One Point Service Technique Troubleshooting Power Amplifiers after Removing Power Transistors New Technique LaserVision with Digital Sound Disc (LDD) New Products NTSC 1 / 2 "...
Various switches and relays are being employed in elec Here we will discuss the features of metal switches and re tronic equipment. They have only one function of open lays employed in Pioneer products. ing and closing electric circuits. Their specifications depend on peripheral circuits.
b) Slide Type Switches A conductive piece slides and engages with the other piece. This has a self-cleaning ability. It scrubs off by itself the A switch completes or breaks the path of a current or sends resistive film of dust and sulfite formed on its contact sur it over a different p a t h .
3 shows a typical power switch. The contact points are m a d e of silver cadmium oxide (AgCdO) and are operated Terminals quickly with the help of a spring. All Pioneer products em ploy power switches which have preliminary been approved Fig. 4 LINEAR Slider Type Signal Selector by the authorities of safety standards in each country.
2.2 S w i t c h e s Classified by F u n c t i o n s cuss signal selectors. This switch is capable of switching multiple circuits when switch wafers are assembled in mul tiple gangs. Generally each wafer can select 11 terminals which are apart from each other by 30°.
b) Push-button Switch A switch IN which a button must be depressed each TIME Nonlock (momentary or press-to-talk) type opens or closes the contacts are to be opened or closed. Microswitch and A circuit only I N the period a key is depressed. Releasing tact switch, however, are excluded from this category.
C) Slide Switch The latter is further divided into t w o . One simply slides The operation of this switch is made by sliding its knob a contact piece back and forth, and the other has a spring back and forth. This is suitable for switching signals be inside and returns the piece to the original position when cause most of this type slide a contact piece on a fixed piece the finger is released.
e) Snap Switch (Toggle Switch) This has a depressing mechanism for operating at a high operational feeling. Here we will discuss the popular mechanically-assisted type employed in D C power supply speed and is mainly used for switching D C power sources circuits and signal senser circuits.
Most of the switches have one or two contact points and nism is required to operate it at a high speed because it circuits because of their structure. A n additional mecha- / has no such mechanism as that of snap switch. Photo 7 Plate Spring Switches g) Microswitch This is cased in a small box, is operated at a high speed...
h) Tact Switch This is A kind of digital switches and is popularly used in key input circuits for digital ICs including microcomputer ICs. Voltage drop by the contact resistance in this switch is negligible because the applied voltage is low (5V — 15V) Insulating rubber and the current is small in digital circuits.
S N - 0 0 0 SNOOOO) Spring S X - 0 0 0 SXOOOO) Others Table 3 Numbering System of Pioneer Switches Coil Yoke Fig. 1 0 Structure of Relay 2 . KINDS OF RELAYS Relays are classified into four; power relay, protective re...
2 . 3 Small Signal Relay Small signal relay is employed in preamplifiers for mut ing, selecting equalizer's time constant, etc. Structure is the same as that of protective relay. This can be made small because it deals with a small current of low voltage. Photo 11 Power Relays Photo 1 3 Small Signal Relay 2 .
Basic Theory of Video Systems NTSC and PAL TV Systems Composite color TV signal includes luminance and chro The main world color TV systems are only NTSC (National minance signals, vertical- and horizontal-sync pulses, Television System Committee), P A L (Phase Alternation vertical- and horizontal-blanking pulses, color-burst sig...
NTSC Ei = 0.74 (E -Ey) 0.27 SYSTEM = 0.48 (E -Ey) + 0.41 O u r eyes are sensitive to orange and cyan on small spots and not so sensitive to magenta and green. When a colored ) signals in TV receiver reproduces ( E ) and ( E thing becomes small, its color approaches orange or cyan.
Then the brightness of 3.58MHz dots is inverted line by signal is called "interleaving". The luminance and carrier line and frame by frame and is made insensible. To avoid color signals ( E n) are represented by the following beating interference between the colour and sound carriers, equations: the horizontal scanning frequency has been determined at 15,734 ( 1 5 , 7 5 0 - 1 6 ) H z .
T o find out the polarity of the modulation axis of fc = (284-1/4) + (f /625) = 4.4336 (ER-EY), burst signal phase is shifted by 90° every line. Provided: = 15,625 If the chrominance subcarrier frequency (Fc) is made a half of the horizontal scanning frequency multiplied by an odd Thus the color carrier energy is interleaved in luminance number as in NTSC system, the (R - Y) component will...
Measuring Instrument Pattern Generator A TV pattern generator is required for testing and adjust the knobs and controls of its front and rear panels. ing VCRs (video cassette recorders), TV receivers and TV The functions of P A L type generators such as Leader's monitors.
®. Color Bars Color bar pattern is composed of color bars in order of luminance. White Yellow Cyan Blue Green Magenta Black Upper pattern: From left — White, yellow, cyan, (75%) green, magenta, red, blue and black Lower pattern: From left — Q, - I , * white and black This signal is for chrominance (chroma) circuit adjustment.
@. Luminance Luminance signal can be removed from the color bar sig nal by depressing this switch. This chroma signal is used to check the phase and amplitude variation of chroma sig nal in the picture amplifier circuit. (Q). Chroma Chrominance level of color bars a n d rasters is variable within the range of ±...
; Lv. Point Service Technique Troubleshooting Power Amplifiers After Removing Power Transistors In the supplement to T U N I N G FORK, "Troubleshooting amplifiers by removing power transistors and heat sinks Power Amplifiers", issued in 1984 we discussed several which occupy large space.
Insert diodes in place of power transistors as shown in Disconnect R l and connect the emitters of Q3 and Q4 with Fig. 3. Leave R l connected. the output terminal via two resistors as illustrated in Fig. 2. Their resistance should be about a half of R l . Low Use powerful rectifying diodes used in mains current rec...
New Technique LaserVision with Digital Sound Disc (LDD) As discussed on the page 74, Vol. 7, NTSC L D D discs have Unfortunately, in the frequency spectrum of P A L LV sys tem, there is no r o o m for the digital sound because the digital sound information in addition to the conventional range of 0-2MHz has already been occupied by two audio analog picture and sound information.
Fig. 3 shows how the digital information is added to the conventional analog information. Digital Analog Waveform Audio Signals Audio Signals Video Signal (2-channels) (2-channels) Video FM signal Frequency Mixer Modulator Audio FM signal Frequency EFM & Modulator CIRC Composite signal Encoder Mixer Signal...
L D D Playback Circuit of CLD-900, N T S C L V / C D com The reproduced R F composite signal is amplified in H E A D patible player (Service Manual VRT-050) A M P and P R E B (Preprocessing b o a r d ) . The signal is am plified again and video and F M sound signals are removed by 1.75MHz L P F in L D D B ( L D D board).
When a C D is played back, L D / C D signal becomes L, the As mentioned, CD player generates 4.3218MHz clock A P C O signal is cut off by Q8, the VCXO frequency is fixed (PLCK) signal and synchronizes it with the suppressed pit- at 8.4672MHz by the voltage set by VR3 while with an repetition signal of the same frequency contained in the L D D disc, this frequency becomes variable in the range...
New Products NTSC 1/2" and 8 mm Home Video Cassette Recorder (VCR) Our home VCRs have recently been introduced into the damentals of the 1/2" nonhi-fi, 1/2" hi-fi and 8-mm home market. The field of VCR is quite a new to us. The knowl VCRs.
Their standards are different as shown on Table 1 to 3. chr ominance(C)-signals, vertical(V)- and horizontal(H)- As to the principle of TV, refer to the Additional Service synchronizing(sync)-signals and audio signal. Although the Manuals, ARP-675 for SD-25 (NTSC) and ARP-928 for basic functions of VCR are similar to those of A C R , there are some important differences.
8 m m /3(NTSC) VHS(NTSC) Remarks Remarks NTSC (3\\ /Sill Option Standard Standard Linear Audio Dubbing possible 5 0 - 8 K 5 0 - 1 0 K 5 0 - 7 K Frequency response (Hz) 5 0 - 1 0 K 5 0 - 8 K Depends on tape speed Dynamic range (dB)
The features of VCR not found in A C R are as follows: 1. Structure of V C R a) Broad frequency bandwidth ( D C - 4 . 5 MHz) VCR consists of a tape transport mechanism, a drum scan b) Helical scanning system for achieving high tape-to-head ner, video-, audio-, control- and erase-heads, electronic relative velocity...
1.2 Drum (cylinder) S c a n n e r The Scanner consists of a stationary Lower-drum, a rotary Lower-drums of aluminum alloy are processed in a weather Upper-drum equipped with two REC/PB-video-heads chamber in the accuracy of submicron order. The Lower- diametrically opposite each other, a Drum-motor for turn...
1.3.3 Playback characteristic of video-head In recording and playback, high frequency signal compo wavelength. T o make the playback frequency characteris nents are decreased by spacing loss, core loss, thickness tic flat, compensation is made with a resonant circuit con loss, etc.
2 . 3 Tape T r a c k Pattern points of video tracks at the b o t t o m edge and diagonal vid Fig. 8 shows the track patterns of 1/2" V H S and (3 types. eo tracks between them.
When recording, the video signal is applied to both A- and connecting the two signal, switching noise is generated. To B-heads. In playback, the picked-up signals coming from avoid this, the connection is performed about 7 H before A - and B-heads are alternately switched to make one con V-sync appears or at the bottom of the screen where the tinuous signal channel as shown in Fig.
4, VIDEO Signal PROCESSING ( N T S C ) those of 1/2" VCRs. Let us see how the picked-up video signal is processed refer Many blocks are used in c o m m o n for recording and ring to the following block diagram. Although the diagram is of the 8mm VCR, its basic principles are the same as playback.
4 . 1 . 2 Y-C separation 4 . 1 Recording The Y- a n d C-signals are separated by Y-C separator to 4 . 1 . 1 Automatic gain control ( A G O avoid intermodulation distortion because they have been A clamper fixes the sync tip level and makes the video sig...
4 . 1 . 4 Frequency modulation (FM) By frequency modulation Y-carrier frequency is deviated tributed in the frequency b a n d too broad to be equal in the range between the frequencies assigned to sync tip ized effectively. Y-signal equalization throughout the and white peak.
4 . 1 . 8 Frequency down-conversion 6. H i g h D e n s i t y Recording T h e C-carrier separated by a Comb-filter is frequency- 1/2" and 8mm VCRs employ guard-bandless system to converted from 3.58MHz to about 7 0 0 ± 500kHz. The rea save the tape.
7. Cross-talk Suppression The following methods are taken to suppress cross-talk caused by guard-bandless recording. 7 . 1 Y-signal cross-talk suppression 7.1.1 Azimuth recording To produce the maximum output, the orientation of the nal on adjacent B-tracks, and on the other hand it makes Playback-head should be the same to that of Recording- B-head sensitive to B-tracks a n d insensitive t o A-tracks.
7.1.2 Y-carrier Ih/2 Shifting (NTSC) T h e horizontal sync pulses are aligned in the track pattern when recording in /3 1-hour or VHS 2-hour mode as shown in Fig. 23 (a). With this pattern the cross talk H-sync does n o t interfere with the main H-sync because they are read out at the same time.
7.2.2 Phase Shift (PS) (NTSC) a) In recording the signal on A-tracks is shifted counter c) The returned signal is delayed by 1H and is added to clockwise by 90° (1/4 fH) in every H period and that the nondelayed signal. Then t h e cross-talk component on B-tracks clockwise by 90°.
9. Servo S y s t e m ( N T S C ) Drum servo system: Precise servo system for capstan and d r u m m o t o r is re quired to draw a specified pattern on the tape in record In recording, the signals generated by Drum-frequency- ing and t o trace it correctly in playback.
SP/LP/EP Capstan FG Speed Motor Divider Det. Drive Capstan Motor Phase Comp. Control Head PB (8mm: Fixed to REC) PB (0, V H S : Fixed to REC) Video Input V sync. Sep. 30Hz PB(# (ft VHS) 3.58MHz Tracking Divider X'tal OSC M M V REC(VHS)
1 1 . Trick P l a y Trick play such as STILL, SLOW and P I C T U R E track center and to make the crossing point of the track boarder away from the center. S E A R C H is possible by shifting tape speed. Tracking con trol becomes difficult when the tape speed varies because In this way the noise still remains in the picture.
1 1 . 5 PICTURE SEARCH In S E A R C H mode, heads cross many tracks and repro duce many noise bars as shown in Fig. (b). As mentioned, 2-head VCR produces noise while the A head is sliding on B-tracks and the B-head is o n A-tracks. To suppress the level variation and noise bars Automatic Gain Control (AGC) circuit smoothes the envelope peaks as shown in Fig.
1 2 . Tuner VCR has a TV tuner a n d an antenna selector for record demodulation, this system provides hi-fi sound by sup ing a TV program a n d an R F converter for putting out pressing video signal interference.
A(L) 1 4 . 2 V H S Hi-fi A(R) VHS Hi-fi system employs two additional audio heads with an azimuth of + 30° or - 30° on the d r u m as shown in Fig. 35. After F M audio signals of 1.3MHz a n d 1.7MHz are recorded deeply, video signals are recorded shallowly (MHz) by ±...
b. Small cassette Features of 8mm video cassette Metal tape has made the cassette small as shown in Fig. 38. a. N o tape guide The volume is 1/4 ~ 1/6 of that of 1/2" cassette tapes. b . Double-wall tape protector The tapes of 13/xm and 10/an thick play 90min and 120min c.
Tape « / „ 46.145kHz - 3 / 46.259kHz Video 16.407kHz 16.521kHz Head Pilot signal shifts here X integer -102.544kHz-(378/ )/58«-CH1 -118.951kHz-(378/ )/50-CH2 =165.210kHz-(378/ )/36 - CH3 =148.689kHz-(378/ )/40 - CH4 (a) When tape is slow. - - 1 4 d B (375/ in PAL) (b) Pilot frequency (NTSC)
e. PCM audio channel Drum Video head A The tape spares P C M area for the additional 2-channel au Tape Plays PCM tracks dio information by wrapping itself over the D r u m by 220° while the conventinal VCR tape wraps the D r u m a little larger t h a n 180°.
4 bytes. 180° g. PCM audio recording Pioneer has developed a compatible 8mm VCR-ACR Extended VE-D70 which can also be used as a P C M audio tape deck. tracks It records for 9 hours with a 90-min tape and 24 hours with a 120-min tape (1/2 speed) in PCM-multi mode.
This publication is to supplement service manuals with descriptions of fundamental techniques. Your frank ad vices, opinions and requests on this publication will be highly appreciated. Your contribution with technical knowhow, hints and ideas found in your field service and with news and topics in your daily life is also welcome.
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