Teac EU-68 User manual

SERVICE MANUAL
EU-68
68cm CTV
Effective: JANUARY,2000 EU68SERV

TECHNICAL BULLETIN 02-Jun-00
Page 1of 1
MODEL: EU-51/80 ST
PROBLEM:
Power supply problem
File: EU51-80 chopper tb.doc
The chopper transistor Q802 is damaged as a consequence of a fault in D816. This problem normally
occurs when a diode type UF5407 is used in the position D816.
Instructions
Replace damaged components. Use only a diode type BMY36D for the position D816.
Regards,
Alcides Berta
TEAC Australia Pty Ltd.

TECHNICAL BULLETIN 26-Jun-00
Page 1of 1
MODEL: EU 51 / 66 / 68 / 80 ST
PROBLEM: CRT output IC protection
File: EU51-80 spgap tb.doc
This is a tentative solution to avoid damages to the output video amplifier IC901 (TDA6107) caused by
electric discharges between electrodes of the CRT. The modification should be applied to units found
with damaged video amplifier IC.
Instructions
Add the following components to the
CRT board. Refer to the figure and
table below for parts location and
specifications.
Components information
Item
Part Number Description From To Comments
1EUSPARK 300V Spark gap Point G Aqua
2EUSPARK 300V Spark gap Ground Aqua
Spark gap
devices have no
polarity
3QDTBOUZ6R2BS Zenner diode
6V2 400 mW 1-PL901 (Cathode) Ground (Anode)
Regards,
Alcides Berta
TEAC Australia Pty Ltd.

1

2
DO NOT CHANGE ANY MODULE UNLESS THE SET IS SWITCH OFF
The mains supply side of the switch mode power supply transformer is live.
Use an isolating transformer.
The receivers fulfill completely the safety requirements.
Safety precautions:
Servicing of this TV should only be carried out by a qualified person.
- Components marked with the warning symbol on the circuit diagram are critical for safety and must only be replaced with an identical
component.
- Power resistor and fusable resistors must be mounted in an identical manner to the original component.
- When servicing this TV, check that the EHT does not exceed 26kV.
TV Set switched off:
Make short-circuit between HV-CRT clip and CRT ground layer.
Short C804 (150mF) before changing IC802 or other components in primary side of SMPS.
Measurements:
Voltage readings and oscilloscope traces are measured under following conditions.
Antenna signal 60dB from colourbar generator. (100% white, 75% colour saturation)
Brightness, contrast, colour set for a normal picture.
Mains supply, 220VAC, 50Hz.
PERI-TV SOCKET
SCART 1 (SC050) SCART 2 (SC051)
1 Audio right output 0.5Vrms / 1K 1 Audio right output 0.5Vrms / 1K
2 Audio right input 0.5Vrms / 10K 2 Audio right input 0.5Vrms / 10K
3 Audio left output 0.5Vrms / 1K 3 Audio left output 0.5Vrms / 1K
4 Ground AF 4 Ground AF
5 Ground Blue 5 Ground Blue
6 Audio left input 0.5Vrms / 10K 6 Audio left input 0.5Vrms / 10K
7 Blue input 0.7Vpp / 75ohm 7 Blue input 0.7Vpp / 75ohm
8 AV switching input 0-12VDC /10K 8 AV switching input 0-12VDC /10K
9 Ground Green 9 Ground Green
10 - 10 -
11 Green input 0.7Vpp / 75ohm 11 -
12 - 12 -
13 Ground Red 13 Ground Red
14 Ground Blanking 14 Ground Blanking
15 Red input 0.7Vpp / 75ohm 15 -
16 Blanking input 0-0.4VDC, 1-3VDC / 75ohm 16 -
17 Ground CVS output 17 Ground CVS output
18 Ground CVS input 18 Ground CVS input
19 CVS output 1Vpp / 75ohm 19 CVS output 1Vpp / 75ohm
20 CVS input 1Vpp / 75ohm 20 CVS input 1Vpp / 75ohm
21 Ground 21 Ground
* * ALL WIRES TO FRONT PANEL & LOUD SPEAKERS MUST BE ZIP-TIED TOGETHER AFTER ANY KIND OF REPAIREMENT
1. INTRODUCTION
11AK19 is a 90ø and 110ø chassis capable of driving 20-21,24,25,28-29,32,33 tubes at appropriate currents.
The chassis is capable of working in both PAL and SECAM. The sound system is capable of giving 6watts
RMS output into a load of 8ohms.
One 8 page simple TELETEXT, TOPTEXT and FASTEXT is provided.
The chassis is equipped with 21-pin scart connectors which can accept via scart the SVHS format from VCRs so equipped.
2. SMALL SIGNAL PART WITH TDA884X
The TDA8840/8842/8844 combine all small signal functions required for a colour TV receiver, except tuning.
2.1. Vision IF amplifier
The IF-amplifier contains 3 AC-coupled control stages with a total gain control range which is higher than 66dB.
The sensitivity of the circuit is comparable with that of modern IF-IC s. The video signal is demodulated by means of a PLL
carrier regenerator. This circuit contains a frequency detector and a phase detector. The AFC output is obtained by using the
VCO control voltage of the PLL and can be read via the I²C-bus. For fast search tuning systems the window of
the AFC can be increased with a factor 3. The setting is realised with the AFW bit.
Depending on the type the AGC-detector operates on top-sync level (single standard versions) or on top sync and top
white-level (multi standard versions). The demodulation polarity is switched via the I²C-bus. The AGC detector time-constant capacitor
is connected externally. This mainly because of the flexibility of the application. The time-constant of the AGC system during positive