Rediffusion MK12W Repair and Interface

[TonyWilk]

Had a job for a mate down the pub to fix up an old telly for him, turns out it was a B/W Rediffusion MK12W.

I've written a document on how I fixed and interfaced to this set (with a home-brew 'rediffusion' modulator) (see below).

I also found a partial service manual for this set (couldn't find anything online) so I've linked this below along with the somewhat remarkable tale of how I rediscovered it.

Yours,
TonyWilk

http://tonywilk.synology.me/rediffusion - my web page with info and documents
(can't attach pdf files here 'cos they're too big)

[Victor-T]

Brilliant tale, can't wait for part II!

[Graham G3ZVT]

I used to look after all the "domestic" TV sets on the Granada TV site on Quay St Manchester. They were all Rediffusion "Doric" cable sets on a Redifusion system (actually Top Rank to be pedantic).

When domestic video recorders became a thing it presented a problem of how to record from the system and playback to the TV

This was solved, I suspect at great expense, by commissioning the design and manufacture of a "modem" unit that sat between the TV and VHS converting the Reduffusion RF signal to CVBS in either direction.
The sound of course, being baseband, was trivial.

[Bobdger]

yep, a Mains powered translator box was available from Rediffusion, the front end used the tuner / i.f panel from the mk4. I only meet a few when customers moved into our area, as the only cable system near us was Brighton.
Bob

[Vintage Engr]

Brilliant Job.
I know the MK12 from many years back. As well as using them on an H.F. network, we used to modify a lot of these for composite video in, & also adding an isolating transformer..

I do have a full service manual, but for the MK12A, the aerial version. I can't find the MK12W, although I should have it somewhere!

David.

[ortek_service]

Originally Posted by Bobdger

yep, a Mains powered translator box was available from Rediffusion, the front end used the tuner / i.f panel from the mk4. I only meet a few when customers moved into our area, as the only cable system near us was Brighton.
Bob

Yes, I remember Stan Willets in West Bromwich having loads of those boxes, selling these at £10? each (unused?) surplus back in the 80's, with their large circular plug to go to the TV from the Modulator board.
I've still got one, that I converted to just use the tuner front-end board, to provide the Sound IF to a NICAM sound Module I got for Stereo sound via HiFi - when new TV's were only just starting to have that.

[toprepairman]

On the wired distribution system the audio was sent out via Quad II's, all 100V line versions.

[dave walsh]

This is a very interesting thread, started by Tony. I lack his level of technical ability but I do have some experience of Cable TV. Most people don't know that that this was pioneered in the UK and not just related to the "cable Guy" that they have in the United States. In the 50's the signal from Winter Hill only reached the Southern end of the Ramsbottom Valley... Holcombe Hill was in the way!. This resulted in a wired Rediffusion System being established and there was shop on Bolton Road West up until the mid eighties! The transmission was through twisted pairs [at 9 megs I think] When I moved into the Centre of the Universe, ie Ramsbottom [in 1974] I was shown the system in a local man's home ie a rotary switch on the wall [free radio channels as well] and a TV with no tuner! I didn't ever sign up with Redifusion as there was a relay in the valley by then so I had a conventional aerial. So there was a two tier system in the town and those with Rediffussion seemed to be particularly proud of it!

When Ch4 came into being we were one of the last places to get it. The excuse was no room in the relay transponder or something like that. Eventually Rediffusion produced a box of electronics, possibly having some similarity to the Convertor that Tony is working on now? It added CH4 to the cable system giving them a commercial lead perhaps but at £50 each it was a great deal money back then. In more recent times I tried to find an example of the box or a Tunerless TV but without much success locally. I never came across a box but thanks to Mike Barker of the Forum who transported a TV to Golborne for me. I have it on display in Rammy and I used to enjoy asking people what was missing from it?

When I started to spend time in Bexhill I noticed a Rediffusion plate [about 9" square] in the pavement one day. I discovered that there had been a cable company operating out of Hastings as well. I had been told that TV Transmissions were plagued by 405 line broadcasts [especially in the summer]. It seemed to be a harmonic [the French 819 line signal was near enough double and that could produce a ghost image behind the UK one]. I think there may have been cable in Shoreham on Sea as well, where my brother in law lives.

Going back to Tony's efforts in Hull, I lived there for over a year and continued to vist for some time. I nearly stayed on as it was a great place. I wasn't aware of Redifussion in the City though [I lived in Anlaby Road near the baths]. I recall being able to enjoy broadcasting from Yorkshire TV and also East Anglia when one of them closed down late at night. Happy days!

Dave W

If anybody's interested in cable threads, there's one by Biggles "Rediffusion How Did It Work?" 23/8/16 or see posts by Dave Moll.

[hamid_1]

That's a nice restoration of what must be a very rare TV nowadays.

I remember seeing the same Rediffusion Avon black and white TV in Bristol in the early 1980s - it was old-fashioned even then. At the time I thought "Avon" meant the set was made for use in the County of Avon which Bristol was then in, but in fact it's the model name of the set. They were distributed all over the country wherever Rediffusion had a presence.

I lived on the edge of Bristol where there was no Rediffusion cable service, but sometimes old Rediffusion TVs like this one would appear dumped on the roadside. They were a source of valves and other components. I did know people in other parts of Bristol who had Rediffusion cable TV. It fascinated me that radio programmes and TV sound came out of the TV speaker even when the television set was switched off and unplugged from the mains. The speaker was powered from the cable network itself, a legacy from when Rediffusion first began distributing radio to people's houses before they had electricity at home. Indeed old Rediffusion speaker boxes (for sound only) sometimes turned up on the unofficial roadside dump.

Over time, Bristol's Rediffusion cable network evolved. The introduction of Channel 4 saw subscribers issued with a UHF aerial and a set-top box called a Translator. This contained a normal terrestrial TV tuner and audio amplifier, allowing the cable TV set to receive ordinary broadcast TV as well as enabling a regular video cassette recorder, home computer or video game to be connected to it.

Granada then acquired Rediffusion, keeping the TV rental business but sold the cable TV side to Robert Maxwell, then owner of the Daily Mirror newspaper. Maxwell Cable TV stopped offering regular terrestrial TV and radio, instead they supplied some premium subscription channels like Prem1ere Movies (this was before Sky launched their satellite TV service, so the extra channels were a big deal). To use the cable service with a regular video recorder, the customer had a brick-sized RF modulator fixed to their wall. The VCR or another TV could be tuned in to the cable TV channel selected by a rotary switch on the wall. Picture quality was rather poor, though. Eventually another company, United Artists Cable arrived in Bristol. They built a new broadband network using Jerrold equipment from the USA which offered many more channels as well as telephone service. The old Rediffusion network faded away.

The redundant Rediffusion Translator boxes were sold off years ago, sometimes modified for use with composite video computer monitors, enabling them to receive regular analogue TV with sound. Some boxes were stripped for parts to build 405-line TV modulators. The converter boxes still turn up for sale at amateur radio rallies occasionally. I've acquired a couple of them, just in case a Rediffusion Avon (or similar) TV should show up. But it's good to see someone has designed a solution that works for the latest formats (blu-ray, HDMI) and is keeping a piece of history alive.