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Forum 135

Tech Chat Mullard Application Laboratory - Teletext

General Technical Discussion

Last Post by Doz 3 weeks ago

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crustytv

(@crustytv)

Posts: 12234

Vrat Founder Admin

Topic starter

In the early 1980s, Mullard manufactured some of the earliest teletext decoding modules made in the UK. I recently acquired this C.C.T Evaluation board that would appear to be from their application laboratory. It has a serial number PT905-42-1 I wonder, could PT indicate Prototype?

It certainly is a curiosity, with a set of eight toggle switches at the bottom of the board. Three i.c's appear to be missing, IC3, IC9 & IC10. I wonder if IC9 & IC10 would have been additional memory decoders and IC3 the SAA5012 which is sitting on the veroboard.

Thought this would be an interesting and worthy of sharing for discussion.

There's nothing I can do with this, it's just a nice piece in the lifecycle of Teletext development in the UK. I shall frame it to hang on the wall in the museum, in the teletext section, along with the decoders, set top boxes and other ephemera.

A little research found this from a Mullard Technical publication.

CrustyTV Television Shop: Take a virtual tour
Crusty's TV/VCR Collection: View my collection
Crustys Youtube Channel: My stuff
Crusty's 70s Lounge: Take a peek

Posted : 13/09/2024 11:42 am

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Mullard Teletext Prototype

Jayceebee

(@jayceebee)

Posts: 2088

Prominent Member Registered

Very interesting piece, given the four memory IC's I would hazard a guess that this is a development board for Fastext. Obviously the extra RAM is for the stored red, green, yellow and blue pages. Strange the addition of the SAA5012 TIC as it was incorporated in the SAA5240?

John.

Posted : 13/09/2024 6:29 pm

Michael Dranfield

(@michael-dranfield)

Posts: 275

Reputable Member Registered

That's a very nice proto board you have there, I had a wireless world teletext module a few years back but sold it on e Bay.

Posted : 13/09/2024 6:52 pm

irob2345

(@irob2345)

Posts: 624

Honorable Member Registered

That's an early CAD layout board. Looks very much like what I was doing in those days, using AutoCad, prior to the existence of dedicated PCB CAD software.

The "stretch" and "array" commands were great for doing memoru arrays and the like.

We'd output the artwork at 2X actual size using a Roland flat-bed pen plotter. It took ages and sometimes a pen would run out of ink and you'd have to start over. Then it was photo-reduced to make the transparency.

Later we found we could go direct to the transparency using an early laser printer that would accept HPGL input via a serial port.

My how things have changed!.

Posted : 13/09/2024 9:46 pm

Doz

(@doz)

Posts: 1537

Prominent Member Registered

Posted by: @irob2345

↑

That's an early CAD layout board. Looks very much like what I was doing in those days, using AutoCad, prior to the existence of dedicated PCB CAD software.

Dedicated PCB software existed long before autodesk. I was using Racal redboard in the 80's , and it was considered old then.

Posted : 14/09/2024 10:17 am