UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Television Standards Converters, Modulators etc

Notices

Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

Reply
 
Thread Tools
Old 13th Dec 2020, 5:26 pm   #1
1980s_john
Triode
 
Join Date: Apr 2005
Location: Ipswich, Suffolk, UK.
Posts: 28
Default Homemade Teletext decoder (based on Mullard Module)

Hi,
Clearing out a cupboard I came across a Teletext decoder box I put together in the late 80s based on a Mullard VM 6101 module. The module has these 4 ICs:

SAA5020 Teletext Timing Chain Circuit
SAA5030 Teletext Video Processor
SAA5040A Teletext Control and Data
SAA5050 Teletext Character Generator

I gutted a push button telephone to make the keyboard, and it plugged the box into a Grundig portable 14" TV (long gone) which had a SCART socket plus a DIN socket for fast video blanking.

I'm sure I had the datasheet for the module but I can't find it, can anyone oblige please?

Thanks,
John

PS As to generating Teletext, I think last time I used a VCR with some suitable recordings off-air.
1980s_john is offline   Reply With Quote
Old 13th Dec 2020, 10:23 pm   #2
Philips210
Octode
 
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 1,819
Default Re: Homemade Teletext decoder (based on Mullard Module)

Hi.

I used to have the Mullard data on the VM6101 Teletext decoder but sadly it has long gone. There is some info in Television magazine. Have a look in the following issues:
Dec 1986, Jan 1987, Sep 1987 and Aug 1988. There is useful details on using the module in those articles. World Radio History has these issues available.

Regards,
Symon
Philips210 is offline   Reply With Quote
Old 13th Dec 2020, 11:48 pm   #3
1980s_john
Triode
 
Join Date: Apr 2005
Location: Ipswich, Suffolk, UK.
Posts: 28
Default Re: Homemade Teletext decoder (based on Mullard Module)

Thanks for heads up on the Television articles. I can't remember where I bought the module from but 15-20 seems right. Most of the design in the Television adapter is about the the keyboard interface. I used an EPROM to map from the 4x4 telephone keypad to the 7-bit code that the Mullard required as shown in the Dec 1986 article (I was limited to 14 different codes so picked what I thought were the most useful). As my TV had RGB + sync + blanking input there was no need for a UHF modulator. It really was a hack but it worked well.

Regards,
John
1980s_john is offline   Reply With Quote
Old 14th Dec 2020, 12:15 am   #4
KeithsTV
Nonode
 
KeithsTV's Avatar
 
Join Date: Aug 2007
Location: South Bradford, West Yorkshire, UK.
Posts: 2,387
Default Re: Homemade Teletext decoder (based on Mullard Module)

There's a circuit for a teletext decoder using the Mullard ICs in the September 1980 Practical Electronics.
https://worldradiohistory.com/UK/Pra...0-09-S-OCR.pdf

I bought a surplus Mullard decoder in 1981 and using that circuit as a reference got it going. I also had the datasheets for the four ICs which allowed me to build a circuit to generate the control signals for it. I later wrote a program for my Acorn Atom to control it. It worked very well using a video output from my Thorn 1590 chassis TV and feeding the video output from the decoder into a monochrome monitor.

Keith
KeithsTV is online now   Reply With Quote
Old 14th Dec 2020, 1:16 am   #5
rambo1152
Nonode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 2,426
Default Re: Homemade Teletext decoder (based on Mullard Module)

I had a Thorn 8000 in the kitchen that I added Teletext using the Mullard board.
I think I had to add a IR remote decoder on a bit of Varoboard
__________________
--
Graham.
G3ZVT
rambo1152 is online now   Reply With Quote
Reply

Thread Tools



All times are GMT. The time now is 5:49 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Copyright ©2002 - 2020, Paul Stenning.