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D.I.Y. TELETEXT DECODER PROJECT

In this concluding part we give full constructional details for this superb design from GMT Electronics.

Since we published the first part of their design last month, GMT have made some improvements to the kit for the Teletext decoder. The main change is a combining of boards three and four into one. Effectively board four has ceased to exist! This simplifies construction still further and has our endorsement. We are republishing the combined circuits here to make things clear. 

CONSTRUCTION
Putting together the unit should be very straightforward. The PCBs should be carefully assembled, following the overlays shown here. Check IC orientation especially closely as that chip set is very expensive to blow just because you didnít want to spend five more minutes doing that boring bit of re-checking. When completed the boards should be interconnected following the wiring schedule given in this article. Check this carefully also.

Board 1 | Board 2 | Board 3

BOARD INTERCONNECTION WIRING
FROMLOCATION-BOARDTOLOCATION-BOARDCOLOURCABLE TYPECOMMENTS
AE.SKT.CHASSISE12 COAXOUTER
AE.SKT.CHASSISMOD 2012 COAXINNER
E22-VE C1CHASSISBLACK  
P2-VE C1CHASSISRED  
E32TR 1CHASSISBLACK INNER SEC TAGS
TR12TR 1CHASSIS  OUTER SEC TAGS
TR22TR 1CHASSIS  OUTER SEC TAGS
E42E41 COAXOUTER
V2V1 COAXINNER
E52E51BLACK  
E92E93 COAXOUTER
K2K3 COAXINNER
E72E73 COAXOUTER
V2V3 COAXINNER
E83O/P SKTCHASSIS COAXOUTER
T3O/P SKTCHASSIS COAXINNER
E13E11 COAXOUTER
A3MOD 2011 COAXINNER
E61E63BLACK  
5V25V1YELLOW UNDER BOARD
12V212V1PINK UNDER BOARD
5V15V3YELLOW BY IC105
12V112V3PINK BY IC105
R1R3RED BY IC105
G1G3GREEN BY IC105
B1B3BLUE BY IC105
S1S3GREY BY IC105
C1C3BROWN BY IC105
M1M3ORANGE BY IC105
1112   
12LED 1CHASSIS   
2122   
21LED 2CHASSIS   
3132   
32LED 3CHASSIS   
4142   
42LED 4CHASSIS   
L2LED 1 to 4CHASSIS   
0101WHITE  
P1P1WHITE  
Q1Q1WHITE  
T1T1WHITE  
U1U1WHITE  
N1N1WHITE  
W1W1WHITE  
X1X1WHITE  
Y1Y1WHITE  
Z1Z1WHITE  
B1*EARPIECECHASSIS   
L51LED 5CHASSIS   
H1TRANSDUCERCHASSIS   
E1TRANSDUCERCHASSISBLACK TRANSDUCER CASE
12V1*EARPIECECHASSIS   
12V1LED 5CHASSISPINK  

SETTING UP
Once the boards are assembled, follow the setting up procedure given in last monthís article to complete the unit. It is worth remembering that to be sure of a good Teletext picture, you need a strong signal at the input. In areas of poor reception it is well worth investing in that better aerial wot you never got 'round to getting...


Find out when it is supposed to rain. All you need is Teletext!
BUYLINES

The designers of this project - GMT - have a complete kit of parts available. This includes all metalwork, PCBs and hardware. A manual is also included. Cost is £155 plus VAT (total £178 inc p&p).

As an alternative the teletext decoder board and control system is available separately at £125 for those who wish to wire into their own television.

PCBs and chip sets are available separately also - but are P.O.A.

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