Memory
initialization, Gray scale adjustments, AGC and AFT adjustments, system control
IC pin description and more… TDA8362,TDA7263, LA7833
Power source: ac 220~240v 50hz
Television system system: b/g, i,l/l’
Color system: PAL/SECAM
Receiving channel VHF: E2~E12
CATV: x,y,z, S1~S41
UHF: #21~#69
Aerial input impedance - 75Ohm
Power
supply
The power supply circuit of the EB3-A chassis is composed of a rectifier smoothing circuit, an oscillation circuit, a control circuit and an output rectifier circuit. the ac input voltage is full-wave rectified by the rectifier smoothing circuit, and an unstable dc voltage is generated at both terminals of the smoothing capacitor C307. This voltage is input to the oscillation circuit. The oscillation circuit is provided with a blocking oscillator circuit that switches the switching FET Q301 on and off, and an oscillation frequency and a duty square wave pulse are generated in the input winding according to operation of the control circuit. A square wave pulse whose size is dependent on the turn ratio of the input and output winding is obtained in the output winding. This is rectified in the output rectifier circuit, and the desired dc voltage is obtained.
The power supply circuit of the EB3-A chassis is composed of a rectifier smoothing circuit, an oscillation circuit, a control circuit and an output rectifier circuit. the ac input voltage is full-wave rectified by the rectifier smoothing circuit, and an unstable dc voltage is generated at both terminals of the smoothing capacitor C307. This voltage is input to the oscillation circuit. The oscillation circuit is provided with a blocking oscillator circuit that switches the switching FET Q301 on and off, and an oscillation frequency and a duty square wave pulse are generated in the input winding according to operation of the control circuit. A square wave pulse whose size is dependent on the turn ratio of the input and output winding is obtained in the output winding. This is rectified in the output rectifier circuit, and the desired dc voltage is obtained.
IF
& deflection (TDA8362)
the if output signal from the tuner passes through the saw filter, and it is input to pin45 and pin46 of IC101. the signal input to the IC passes through the if amplifier, video detection and video amplifier circuits and is output from pin7 as a composite video signal. And after this signal is converted to impedance at Q122, supplies to the video and chroma amplifier stages. The sync.-separation circuit separates the video signals applied to pin13(internal video signal) or pin15(external video signal) to vertical- and horizontal-sync signals respectively. The horizontal oscillator requires no external components and is fully integrated. The oscillator is always running when the start-pin36 is supplied with 8v. Horizontal drive signal is output from pin37. VR401 is for adjustment of the horizontal centering. The separated vertical-sync signal from sync: separation circuit passes through the vertical-separation circuit, and applied to trigger divider circuit. the horizontal oscillation pulse and input vertical sync. pulse are monitored by the trigger divider circuit, and switching 50Hz and 60Hz system, the vertical amplitude automatically adjusted for 50Hz and 60Hz. the output signal from the trigger divider is triggered vertical oscillation circuit consisting of C401, R402 and pin42, and vertical drive pulse is output from pin43. VR451 is for changing the amount of AC feedback applied to pin41 and for adjustment of the vertical amplitude.
the if output signal from the tuner passes through the saw filter, and it is input to pin45 and pin46 of IC101. the signal input to the IC passes through the if amplifier, video detection and video amplifier circuits and is output from pin7 as a composite video signal. And after this signal is converted to impedance at Q122, supplies to the video and chroma amplifier stages. The sync.-separation circuit separates the video signals applied to pin13(internal video signal) or pin15(external video signal) to vertical- and horizontal-sync signals respectively. The horizontal oscillator requires no external components and is fully integrated. The oscillator is always running when the start-pin36 is supplied with 8v. Horizontal drive signal is output from pin37. VR401 is for adjustment of the horizontal centering. The separated vertical-sync signal from sync: separation circuit passes through the vertical-separation circuit, and applied to trigger divider circuit. the horizontal oscillation pulse and input vertical sync. pulse are monitored by the trigger divider circuit, and switching 50Hz and 60Hz system, the vertical amplitude automatically adjusted for 50Hz and 60Hz. the output signal from the trigger divider is triggered vertical oscillation circuit consisting of C401, R402 and pin42, and vertical drive pulse is output from pin43. VR451 is for changing the amount of AC feedback applied to pin41 and for adjustment of the vertical amplitude.
Video
chroma & r.g.b. (tda8362)
The composite video signal output from the pin7 of ic101 passes through q122/q124, and it is supplied to pin13. The external video signal output from SCART is supplied to pin15. The video signal input to pin13 or pin15 is separated to luminance (y) signal and chroma signal in IC101. These pins are used in common with h/v-sync; separation input. The peaking of y signal is adjusted by dc voltage of pin14. (“sharpness” control) the chroma signal is divided into r-y and b-y chroma signals, demodulated in IC101, and output from pin30 (R-Y) and pin31 (B-Y). These chroma signals pass through the 1h delay line circuit (IC270), and they are input to pin29 (R-Y) and pin28 (B-Y). These R-Y/B-Y signals pass through RGB matrix circuit and RGB selector circuit of IC101. the internal RGB signals are generated in RGB matrix circuit and the RGB selector, consisting linear amplifiers, clamps and selects either the internal rgb signals or the external rgb signals input
from pin22(R), pin23(G), pin24(B). Selection is controlled by the voltage at the RGB switch control (pin21) and mixed RGB modes are possible since RGB switching is fast. The RGB switch also functions as a fast blanking pin by blanking the RGB output stages; here internal and external RGB signals are overruled. The color gain is controlled by dc voltage of pin26. (“Color” control)
The contrast control voltage present at pin25, and the brightness control voltage present at pin17 controls dc level of RGB signals. The RGB signals are finally buffered before being available at the RGB output pins [pin20 (R), pin19 (G), pin18 (B)]
The composite video signal output from the pin7 of ic101 passes through q122/q124, and it is supplied to pin13. The external video signal output from SCART is supplied to pin15. The video signal input to pin13 or pin15 is separated to luminance (y) signal and chroma signal in IC101. These pins are used in common with h/v-sync; separation input. The peaking of y signal is adjusted by dc voltage of pin14. (“sharpness” control) the chroma signal is divided into r-y and b-y chroma signals, demodulated in IC101, and output from pin30 (R-Y) and pin31 (B-Y). These chroma signals pass through the 1h delay line circuit (IC270), and they are input to pin29 (R-Y) and pin28 (B-Y). These R-Y/B-Y signals pass through RGB matrix circuit and RGB selector circuit of IC101. the internal RGB signals are generated in RGB matrix circuit and the RGB selector, consisting linear amplifiers, clamps and selects either the internal rgb signals or the external rgb signals input
from pin22(R), pin23(G), pin24(B). Selection is controlled by the voltage at the RGB switch control (pin21) and mixed RGB modes are possible since RGB switching is fast. The RGB switch also functions as a fast blanking pin by blanking the RGB output stages; here internal and external RGB signals are overruled. The color gain is controlled by dc voltage of pin26. (“Color” control)
The contrast control voltage present at pin25, and the brightness control voltage present at pin17 controls dc level of RGB signals. The RGB signals are finally buffered before being available at the RGB output pins [pin20 (R), pin19 (G), pin18 (B)]
Audio output (TDA7263M)
The audio signals output from the audio unit are input to pin1(L) and 5(R) of ic581 and passes through the preamplifier circuit and drive circuit, after which it is input to the audio amplifier. The audio amplifier is an SEPP (Single-Ended, Push-Pull) OTL type and output to pin8(R) and 10(L) to directly drive the speakers
Vertical output (LA7833)
an IC (LA7833) is used for the vertical output circuit in this chassis. The vertical drive pulse from pin43 of ic101 is input to pin4 of IC451. This pulse drives IC451; and vertical scanning is performed. In the first half of scanning a deflecting current is output from pin2 and
passes through the following path:
vcc(b4) > d451 > pin3 > pin2 > dy > c461 > vr451/r459. an electric charge is then stored in c461.
In the last half of scanning the current path is c461 > DY > pin2 > pin1 > vr451/r459 > c461. in this way, an amplifying saw tooth waveform current flows directly to DY to perform electron beam defection.
Next, in the first half of the banking period the vertical drive pulse suddenly becomes off, and in order to reduce the current flowing to DY, the current path becomes as follows by the inductance of DY:
DY > pin2 > pin1 > vr451/r459 > c461 > dy. also, when the charge of DY has dissipated, the current path becomes vcc24v > pin6 > pin7 > c452 > pin3 >pin2> dy > c461 > vr451/r459, and when the prescribed current value is reached, the vertical drive pulse becomes on. This completes one cycle.
Horizontal output
A horizontal oscillation signal is output from pin37 of ic101 and switches the drive transistor Q431. This switching signal is current amplified by the drive transformer T431 and drives the output transistor Q432.
When Q432 becomes on, an amplifying current flows directly to DY through c441/442 > DY > q432 > Gnd, and defection is performed in the last half of the scanning period. Next, when Q432 becomes off, the charge that had been stored in DY up to that point releases a
resonance current to the resonant capacitors c420 and c423 and charges them. The current stored in c420 and c423 is then flowed back to DY, and an opposite charge is then stored in DY. This opposite charge then switches the damper diode in Q432 ON, the resonance state is completed, and an amplifying current is then flowed again directly to DY through the dumper diode. By this means, deflection in the first half of the scanning period is performed, and when Q432 becomes on at the end of the first half of the scanning period, deflection during the last half is begun, thus completing one cycle.
CPU pin description
pin1: h-sync. input (horizontal pulse for osd)
pin2: v-sync. input (vertical pulse for osd)
pin3: colour control output
pin4: brightness control output
pin5: contrast control output
pin6: sharpness control output
pin7: tint (gnd)
pin8: tv/av output (l:av mode)
pin9: av mode selection output-a
pin10: av mode selection output-b
pin11: natioal select option
pin12: i2c bus scl (serial clock for memory)
pin13: i2c bus sda (serial date for memory)
pin14: not used (+5v through pull up resistor 22k)
pin15: ident signal input (l:no signal)
pin16: r/c signal input
pin17: av1 scart control signal input (vtr play:l)
pin18: av2 scart control signal input (vtr play:l)
pin19: ignor output
pin20: 50/60hz output
pin21/22: gnd
pin23: supply ground
pin24: oscillator input for cpu
pin25: oscillator output for cpu
pin26: supply ground
pin27: power supply(+5v)
pin28: oscillator output for osd
pin29: oscillator input for osd
pin30: reset input
pin31: protect signal input (l:power circuit defects)
pin32: not used(gnd)
pin33: aft signal input.
pin34: text/16:9 select option
pin35: key scan 1
pin36: p-on(text)
pin37: s-vhs output
pin38: gnd
pin39: bg/i select output
pin40: l/l’ select output
pin41: neg/pos select output
pin42: not used (gnd)
pin43: 16:9/4:3 switch output
pin44: not used (gnd)
pin45: not used (gnd)
pin46: not used (gnd)
pin47: mute output in no picture(ftz mute)
pin48: power on/off output (h:on)
pin49: blanking output for osd
pin50: not used (open)
pin51: green output for osd
pin52: red output for osd
Power
supply adjustment
1. set vr351 to be mechanical centre before pressing the main switch.
2. tune the receiver to pal circular pattern.
3. set brightness and contrast controls to normal.
4. connect digital v-meter to test point "tp-b".
5. by using vr351, adjust voltage to 150 ± 0.5 v.
1. set vr351 to be mechanical centre before pressing the main switch.
2. tune the receiver to pal circular pattern.
3. set brightness and contrast controls to normal.
4. connect digital v-meter to test point "tp-b".
5. by using vr351, adjust voltage to 150 ± 0.5 v.
AFT
adjustment
1. b/g/i area : tune the receiver to the clearest station on system bg. by using t121, adjust aft to obtain the best picture.
2. l/l’ area : tune the receiver to vl station on system l/l’. by using vc141, adjust aft to obtain the best picture.
3. if bg/i and l/l’ can be received adjust 1 and 2.
1. b/g/i area : tune the receiver to the clearest station on system bg. by using t121, adjust aft to obtain the best picture.
2. l/l’ area : tune the receiver to vl station on system l/l’. by using vc141, adjust aft to obtain the best picture.
3. if bg/i and l/l’ can be received adjust 1 and 2.
AGC
adjustment
Note: Do not attempt this adjustment with weak signal.
1. tune the receiver to the clearest station.
2. set AGC vr(vr120) in direction which causes snow noise to appear, then in the opposite direction until snow noise just disappears.
Note: Do not attempt this adjustment with weak signal.
1. tune the receiver to the clearest station.
2. set AGC vr(vr120) in direction which causes snow noise to appear, then in the opposite direction until snow noise just disappears.
Grey
scale adjustment
screen vr adjustment
1. tune the receiver to the white pattern.
2. set brightness control to display centre and contrast control to normal.
3. set sw220 to "service" position.
4. set vr602 and vr612 to be mechanical centre.
5. turn vr601, vr611 and vr621 fully counter-clockwise.
6. set screen vr for one colour to be just visible.
bias vr adjustment
7. by using vr601, vr611 or vr621, adjust line to be white.
8. set sw220 to "normal" position.
drive vr adjustment
9. by using vr602 and vr612, adjust white balance.
screen vr adjustment
1. tune the receiver to the white pattern.
2. set brightness control to display centre and contrast control to normal.
3. set sw220 to "service" position.
4. set vr602 and vr612 to be mechanical centre.
5. turn vr601, vr611 and vr621 fully counter-clockwise.
6. set screen vr for one colour to be just visible.
bias vr adjustment
7. by using vr601, vr611 or vr621, adjust line to be white.
8. set sw220 to "normal" position.
drive vr adjustment
9. by using vr602 and vr612, adjust white balance.
High voltage & width adjustment
[high voltage adjustment]
1. tune the receiver to pal circular pattern.
2. set brightness and contrast controls to maximum.
3. connect digital v-meter to both terminals of r232(left side)(+) , and high voltage meter to CRT anode.
4. confirm high voltage to be 26.0 ± 1 kv at beam current 1.3, and less than 29.0 kv at 0 beam current .
[h-width adjustment]
5. adjust vr462 to obtain proper H- width.
6. reconfirm high voltage.
H-center adjustment
1. tune the receiver to circular pattern.
2. adjust h-center by using vr401.
1. tune the receiver to circular pattern.
2. adjust h-center by using vr401.
V-centre
adjustment
1. tune the receiver to circular pattern.
2. adjust V-center by using sw451.
V-size adjustment
1. tune the receiver to circular pattern.
2. adjust v-size by using vr451.
focus adjustment
by using focus vr, adjust focus control for well scanning lines.
1. tune the receiver to circular pattern.
2. adjust V-center by using sw451.
V-size adjustment
1. tune the receiver to circular pattern.
2. adjust v-size by using vr451.
focus adjustment
by using focus vr, adjust focus control for well scanning lines.
Initialization of memory IC
[When you replace a memory ic (IC731), it is necessary to initialize the IC as follows.]
1. Press and hold the function button on the TV set and then press the recall button on the RC transmitter, the following picture will appear on the screen. [Service mode]
Item -1 set> 0
2. Confirm set number of all items is "0" by pressing the function button.
3. If it is not "0", change to "0" by the level (+/-) button. (Changing the set number, automatically memorized.)
4. Press the recall button, to return the normal TV mode.
Stereo separation setting
1. To enter the service mode, press and hold function button on the tv set and then press the function button on the rc transmitter. the following picture will appear on the screen.
k2 > 32 [k2=service code, 32=service number]
2. set the service codes and numbers as below;
k1 > 16
k2 > 32
to change the service code, press the function button.
to change the service number, press the level (+/-) button.
3. Press the recall button to return to the tv mode.
4. Confirm the sound quality with stereo signal receiving.
