Amstrad STV-2104 Schematic

AMSTRAD STV 2104

1

General Information

Satellite Ready

21” Television with Fast Text

Recommended Safety Parts

Item Part No. Description

IC902 253327 IC TLP621
Q402 175665 TR2SD1555E
L401 242040 Coil 54uH HCL-91278-04
T402 241691 Tx Flyback CFO34l
T901 241929 Tx Switching EI-49
S901 241608 Switch Power 01-48

F901 194246 Fuse T4A 250V
R406 242024 2.2 ohm
R409 241520 470 ohm
R423 242025 180 ohm
R468 241513 0.68 ohm 1/2W
R422 241805 0.68 ohm 1W
C423,426,918-922 174811 220pF
C430 176462 680pF
C504-506 176488 1200pF 500V
C420 242036 1200pF
C916 400V 253610 0.0022uF
C413,414 500V 176754 0.0022uF
C903,930,944 500V 242098 0.0047uF
C507 2KV 242098 0.0056uF
C431,509 250V 241711 10uF
C946 160V 100uF
C428,925 200V 150uF
C907 400V 272870 220uF
C417,419 1.6KV 271245 0.0015uF
C901-905 250VAC 253611 0.047uF

241692 C.R.T. 21” A51JSW90X10
242086 AC Line Cord W/Plug Black

Tank Coil Adjustment

Service Adjustments

Signal In:

VIF signal generator. Tuner test point TP and

Safety Tests

Note: When any work is carried out on a set, the
following safety tests must be carried out to
ensure continued electrical safety.

1) Flash Test

Test at 3.5k V between the live and neutral of
the mains lead joined together and ALL
accessible metal points on the exterior of the
set.

2) Insulation Resistance Test

Test between the live and neutral of the mains
lead joined together and ALL accessible
electrical points on the exterior of the set to
show a resistance of at least 4M W.

Alignment Instructions

Test Equipment

1: VIF sweep generator.
2: SIF sweep generator.
3: Colour bar/Dot/Crosshatch generator.
4: DC power supply (14V).
5: Oscilloscope.
6: Vacuum tube voltmeter.
7: Volt ohmmeter.
8: High voltage meter.
9: Ampere meter (0.5 class, DC 3mA max.).
10: Demagnetising coil.
11: Philips pattern generator.
12: Frequency counter.
13: Continuous waveform generator.

tuner case (earth).

Signal Out:

Oscilloscope TP601 and earth.

Method:

1: Adjust AGC bias voltage for maximum

amplitude of waveform.

2: Adjust the output level of VIF sweep genera-

tor to achieve 2Vp-p output on oscilloscope.

3: Adjust T103 to obtain maximum amplitude of

response at PC (38.9 MHz).

Remarks:

1: Refer to fig. 1 and fig. 2.
2: Supply DC 12.5V to “+” lead of TP402

(steps 1 - 4 only).

3: Supply RF AGC bias 5.5V voltage to TP101,

refer to fig. 1a (step 1- 3 only).

4: Check if AGC voltage is 5.5V ± 0.25V.

Fig. 1

Fig. 1a

Fig. 2

VIF Adjustment

Signal In:

VIF signal generator. Tuner test point TP and
tuner case (earth).

Signal Out:

Oscilloscope TP601 and earth.

Method:

1: Connect 100 W resistor between TP102 and

TP 103.

2: Adjust the level of sweep generator for

maximum amplitude of waveform.

3: Increase the output level of sweep generator

to achieve 2Vp-p output.

4: Increase the output level of sweep generator

in 20dB.

5: Adjust AGC bias voltage to achieve 2Vp-p

output.

6: Adjust tuner converter for coil to obtain the

waveform shown.

Remarks:

1: Refer to fig. 3.
2: Disconnect 100 W resistor after satisfactory

results.

Fig. 3

AFC Alignment

Signal In:

VIF signal generator. Tuner test point TP and
tuner case (earth).

Signal Out:

Oscilloscope TP106 and earth.

Method:

1: Adjust the output level of VIF signal generator

for maximum amplitude waveform without
saturation.

2: Adjust T102 to obtain frequency response as

shown in the fig. at 38.9 MHz.

Remarks:

1:Refer to fig. 4.

Fig. 4

SIF Alignment

Signal In:

SIF signal generator TP105 and earth.

Signal Out:

Oscilloscope TP604 and earth.

Method:

1: Connect TP101 (AGC) to earth.
2: Set the frequency of FM signal generator 5.5

MHz with 400 Hz 25 kHz deviation and signal
output level to 100dB.

3: Adjust T104 to obtain the maximum output.

Remarks:

1: Disconnect the TP101 (AGC) to earth after

satisfactory results.

B+ Adjustment

Signal In:

Power on.

Signal Out:

AVO meter.

Method:

1: Connect voltmeter to TP405 and earth.
2: Adjust VR901 to read DC 106.5V ± 0.5V.

Horizontal Circuit Adjustment

Signal In:

Signal generator.

Signal Out:

Frequency counter IC302 pin 41 and earth.

Method:

1:Set the TV to AV mode.
2:Connect the frequency counter between IC302

pin 41 and earth.

3:Adjust VR303 (H. Freq.) to the reading of

15330 ± 30 Hz and back to TV mode.
4:Receive monoscope pattern.
5:Adjust VR301 (H. CEN.) control to obtain

normal picture.

Vertical Circuit Adjustment

Signal In:

Signal generator.

Signal Out:

Frequency counter V-Deflection Yoke and earth.

Method:

1: Set the TV to AV mode.
2: Connect the frequency counter between

V-Deflection Yolk and earth.

3: Adjust VR304 (V-Hold) to the reading

44 Hz +2 -0 Hz and back to the TV mode.
4: Receive monoscope pattern.
5: Adjust VR401 (V-High) control to obtain

normal picture.

White Balance Adjustment

Signal In:

Receive a black and white picture signal.

Signal Out:

Screen.

Method:

1: Set screen control to minimum.
2: Turn R. G. B. VR501, VR502, VR503 and drv.

VR504, VR505 to mid position.

3: Set contrast and brightness controls to mid

position.

4: Connect jumper wire between TP401 and

TP402.

5: Turn screen control clockwise until dim line

appears.

6: Adjust VR501 to get a red H. line, VR502 to

get a yellow line and VR503 to get a white
line.

7: Disconnect the jumper wire after White

Balance Adjustment.

8: Adjust VR504 and VR505 to obtain a white

uniform picture.

Focus

Signal In:

Signal generator.

Signal Out:

Screen.

Method:

1: Set contrast control to maximum.
2: Set the brightness control to mid position.
3: Adjust focus control to get the sharpest

picture.

RF AGC

Signal In:

Signal generator CH 9 (203.25 MHz).

Signal Out:

Voltmeter Tuner AGC.

Method:

1: Set input signal level to 60dB ± 1dB.
2: Connect voltmeter to tuner AGC and earth.
3: Adjust VR101 to read DC 5V +0.5 -0.2V.

Colour DE Mod Adjustment

Signal In:

Signal generator.

Signal Out:

Screen.

Method:

1: Set colour control to maximum.
2: Set contrast control to minimum.
3: Connect oscilloscope to TP406.
4: Adjust CT301, VR302 and T301 to obtain as Fig.

Remarks:

Refer to fig 5.

Make this line
straight
(Adjust CT301)

Reduce difference to
minimum (Adjust T301)

Fig. 5

Reduce
difference to
minimum
(Adjust T302)

Sub Brightness Adjustment

Signal In:

Signal generator.

Signal Out:

Screen.

Method:

1: Select grey scale.
2: Set brightness, contrast and colour to mid

position.

3: Adjust VR305 control until 10th step of grey

scale just appears on the screen.

On Screen Adjustment

Signal In:

Signal Generator.

Signal Out:

Screen.

Method:

1: Press the volume Up/Down key.
2: Adjust T601(OSD CEN.) for adjust the

lettering to centre of CRT.

Teletext Picture Adjustment

Signal In:

Receive a pattern with a Teletext signal.

Signal Out:

Frequency counter TP801 and earth.

Method:

1: Select a Teletext page.
2: Short pin 22 of IC801 to ground.
3: Adjust CT801 until the frequency counter

reading 6.0 MHz ± 0.2 kHz.

Colour Purity Adjustment
See fig. 6.

Fig. 6
Note: Before adjustments described below are

attempted, V-Hold, V-High, B+ Voltage and
Focusing adjustments should be completed.

Method:

1: Place the TV receiver facing North or South.
2: Plug in the TV and switch it on.
3: Operate the receiver for over 30 mins.
4: Fully degauss the receiver by using an

external degaussing coil.

5: Receive a crosshatch pattern and roughly

adjust the static convergence control.

6: Loosen the clamp screw of the deflection

yoke and pull the deflection yoke towards you.

7: Fully turn the red and blue drive (VR504 and

VR505) controls counter-clockwise.

8: Adjust the purity magnets so that green field

is obtained at the centre of the screen.

9: Slowly push the deflection yoke towards bell

of CRT and set it where a uniform green field
is obtained.

10:Tighten the clamp screw of the deflection

yoke.

Adjustments / Adjustments Cont’d / Safety Parts / AV Diagram / IF Diagram / Remote Control Diagram / Main Diagram / Main Diagram Cont’d

Main Diagram (Sat Rec) / LED Diagram / Teletext Diagram / CRT Diagram

AMSTRAD STV 2104

2

Adjustments Cont’d

Convergence Adjustment (see fig. 7)

Fig. 7

Method:

1: Receive a dotted pattern.
2: Un-fix the convergence magnet clamper and

align red with blue dots at the centre of the
screen by rotating (R, B) static convergence.

3: Align red/blue with green dots at the centre of

the screen by rotating (RB-G) static conver­gence magnet.

4: Fix the convergence magnets by fixing the

clamper.

5: Remove the DY wedges and slightly tilt the

deflection yoke horizontally and vertically to

obtain good overall convergence.
6: Fix the deflection yoke by wedges.
7: If purity error is found, follow Purity

Adjustment instructions

SAT Section

AFC Alignment

Signal In:

Power on.

Signal Out:

Voltmeter at TP2.

Method:

1: Adjust VR102 to read 2.9 -3V.

Remarks:

Tuner without signal I/P and loading.

Signal In:

LNB supply alignment

Signal Out:

Voltmeter at tuner LNB input.

Method:

1: Connect 43 W resistor to LNB input.
2: Connect TP1 to GND and power on.
3: Press SEQ. key twice and press select +/-

key to select V-polarisation.

4: Press pre-set key twice until the turning bar

appears.

5: Press select +/- key to adjust LNB voltage to

13.1V ± 0.1V.

6: Press SEQ. key and select +/- key to select

H-polarisation.

7: Press pre-set key twice until the turning

appears.

8: Press select +/- key to adjust LNB voltage to

17.5V ± 0.1V.

SIF Alignment

Signal In:

RF signal generator.

Signal Out:

VTVM and distortion meter at pin 1 and 3 of SAT
SCART.

Method:

1: Receive the correct RF program and audio

channel.

2: Adjust T101 to maximum level output and

minimum distortion output of pin 3 of SAT
SCART.

3: Adjust T102 to maximum level output and

minimum distortion output of pin 1 of SAT
SCART.

Remarks:

1: Pre-set audio mode to stereo and audio

frequency L to 7.02 MHz and audio frequency
R to 7.20 MHz of RF signal generator.

2: Pre-set audio deviation to 100 kHz p-p.

Video DEV. Alignment

Signal In:

RF signal generator.

Signal Out:

Oscilloscope at pin 19 of SAT SCART.

Method:

1: Receive the monoscope pattern.
2: Press SEQ. key and select +/- key to select

16 MHz video deviation.

3: Adjust VR101 to output 1Vp-p.

Remarks:

1: Connect 75 W resistor between ground to

pin 10, pin 12 and pin 19 of SAT SCART.

AV Diagram

IF Diagram

Teletext Diagram

CRT Diagram

Adjustments / Adjustments Cont’d / Safety Parts / AV Diagram / IF Diagram / Remote Control Diagram / Main Diagram / Main Diagram Cont’d

Main Diagram (Sat Rec) / LED Diagram / Teletext Diagram / CRT Diagram

AMSTRAD STV 2104

Main Diagram

3

Adjustments / Adjustments Cont’d / Safety Parts / AV Diagram / IF Diagram / Remote Control Diagram / Main Diagram / Main Diagram Cont’d

Main Diagram (Sat Rec) / LED Diagram / Teletext Diagram / CRT Diagram

AMSTRAD STV 2104

LED Diagram

4

Main Diagram

Cont’d.

Remote Control Diagram

Adjustments / Adjustments Cont’d / Safety Parts / AV Diagram / IF Diagram / Remote Control Diagram / Main Diagram / Main Diagram Cont’d

Main Diagram (Sat Rec) / LED Diagram / Teletext Diagram / CRT Diagram

AMSTRAD STV 2104

5

Main Diagram (Satellite Receiver & Clamping)

Adjustments / Adjustments Cont’d / Safety Parts / AV Diagram / IF Diagram / Remote Control Diagram / Main Diagram / Main Diagram Cont’d

Main Diagram (Sat Rec) / LED Diagram / Teletext Diagram / CRT Diagram