Daewoo DVN-14F6N Service Manual page 44

6. SERVO/SYSCON CIRCUIT OPERATION
1) summary
• When power supply is supplied to TV/VCR, Servo-Syscon 1 Chip IC confirms the driving condition of DECK
by checking CAM SW from DECK. And it gets capstan Motor worked and is operated as initial Mode. This
is ready for receiving the serial data from timer IC after proper operating according to the driving condition
of Deck and the existence of tape or not.
• When Syscon IC received recording signal, playback signal and so on by receiving of pussing button and
using remote control inform Timer IC what button (remote sensor) is pressed as a serial data, Timer IC oper-
ates properly on each mode.
• After making Deck be in proper condition in each mode by driving L/C motor according to each mode, it dri-
ves the drum motor and capstan motor to make the head spin and the tape move. Drum and capstan
servo are operated in order to obtain clear screen condition.
• The special feature of Drum servo system helps to keep the constant speed and phase of it and to prevent the
screen sway up/down.
By comparing with D-FG signal from Drum Motor and referencesignal of Syscon IC to keep the constant
speed, the difference value is put out to DPWM to drive Drum Motor.
By comparing with D-PG signal from Drum Motor and reference signal of Syscon IC (playback Mode) to
keep the constant phase, the difference value and speed difference are put out to D-PWM.
• Capstan servo system keeps the constant speed and phase of tape. It prevents the trembling sound and the
flow of the Noise band on screen. And it prevents a lot of Noise on screen by malfunction of Tracking.
• In order to keep the constant speed, It's put out to C-PWM from caption Motor, DC-amplified in power curcuit
and gets caption Motor drived.
• By comparing with CTL signal from CTL Head connected with the lower section of A/C Head and the
refeence signal of Syscon IC, the value and speed difference are put out to C-PWM.
2) VCR MODE IN NORMAL CONDITION
(1) EJECT
(2) STAND-BY
(3) STOP
(4) FF
(5) REW
(6) REC
(7) PAUSE
(8) PLAY
(9) STILL
(10) CUE & REV : MODE that search the screen right or reversely.
7. NORMAL AUDIO CIRCUIT OPERATION
1. REC Mode
The signal put in to IU01 #16, is amplified at LINE AMP through ALC circuit in the IC. It is put out to speaker
through #22. At the same time it is put out from #21 through High-Frequency compensation circuit by reso
nance block.
After the signal goes through the REC AMP, it's modulated to AM by frequency 70KHz, is recorded on a tape
through R/P Head.
2. PB Mode
After the signal picked up at the HEAD is put in to pin #2 and performs to amplify and equalize frequency at
each mode, it is supplied to OUTPUT #1 SW in IC.
The signal is chosen as normal by Sound Ouptut control, is put in to LINE AMP again and is amplified. Then,it's
put in to TV.
8. VIDEO CIRCUIT OPERATION
1. EE mode
VIDEO input signal is input to #31 of IY01 (LA7423A) and output to #28 of IY01 after it's multiplied 2 times at AGC and
VIDEO AMP. The signal is connected to VIDEO output terminal.
: MODE that a casstte come out of compartment.
: MODE that a cassette is unloading.
: MODE that a casstte is loading.
: Fast Forward MODE that moves the tape forward in STOP mode
: REWind MODE that moves the tape reversely in STOP mode
: RECord MODE that records video and audio signal on tapes.
: record PAUSE MODE that makes recording stop.
: MODE that plays the record tape
: play STILL MODE that playback is paused
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