Rediffusion Frequency Translator : X2  


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06/02/2017 1:15 pm  

A bit of background

At the back end of 2015 I picked up a Rediffusion MK.I CU2213, this being a UHF set. At the same time I picked up a chassis for a Rediffision MK.I wired CH2213. The intention being to use all its panels bar the signals board as spares.

However roll on four months later in March 2016, I managed to get the cabinet and CRT for the CH2213. This changed the plan as now I had an opportunity to preserve a wired set, only problem being to be usable it would need a Frequency translator.

The Rediffusion Frequency Translator ( Telebox)

There was/is a specific box Rediffusion supplied that allowed for a wired set to be used on UHF for normal TV reception. The box was called a Rediffusion "Frequency Translator" and was more commonly known as a "TeleBox". This device takes a UHF TV signal and converts it to the Rediffusion cable TV standard. 

These boxes are rare now and many were carved up to make a 405-line modulators.

Malc's Speedy Spares ( Rentals)

Last summer Malc lent me his translator but one thing lead to another and I never got around to using it. Malc's came from Steve James and looks to have been modified. At the time I had no idea why the knob had been added to the front, neither did Malc when asked (I know now).

Malc's Box


The search is Over, I've found oneTwo

Last week after searching for a Translator of my own for 15 months, two turned up on e-bay, one had been modified.


Box 1

As mentioned above one had been got at, an additional tuner, speaker and again a knob out the front being added. Along the back were RCA and DIN outputs along with an extra switch. This unit was housed in an all plastic cabinet, it also had the wired connection cable plug removed along with the original mains flex, this box will be used for spares.



Box 2

The second box is in much better original condition, its also appears to be an earlier version, the assumption being wood boxes before molded plastic cabinets . This unit rather than being housed in a plastic cabinet is all wood construction, including the lid. I intend to use this one in for the MK.I CH2213. I've no idea if it works but as stated above, the other box will serve as spares should the need arise.

3-1.jpg 4-1.jpg 7-1.jpg

 5-1.jpg 6-1.jpg good1.jpg



A nice chap contacted me via the site, he had the Frequency Translator circuit diagram, MK.I user manual, service technicians installation guide and various other data. All this has been uploaded to the Data Library to compliment the data Malc had already supplied. I've still got to scan the Translator circuit diagram, that should be there shortly.  

Just goes to show, you wait long enough and everything eventually turns up. Hopefully sometime this year I will get the CH2213 up on the bench and see how the set and translator fair.

Crusty's Collection Blogs

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06/02/2017 1:34 pm  

The circuitry and wiring in that box looks very Rediffusion MK 4 like.

"This is my multimeter. There are many others like it, but this one is mine. My multimeter is my best friend. It is my life. I must master it as I must master my life. Without me, my multimeter is useless. Without my multimeter, I am useless."

Katie Bush
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06/02/2017 8:07 pm  

Just throwing a log on the fire, here....

"Box 1" looks to me as though it might have been converted for use as a TV sound receiver? - in a similar fashion to the 'Clarke & Smith' et al, sound receivers available through the RNIB. On the face of it, it's a bit weird having that speaker seemingly connected to an external jack, unless an off-board amp was used?

As to the additional control on the front - audio gain? It certainly looks as if it simply replaces a preset that once resided on the mainboard. I suppose the obvious question is; what was the original preset meant to do?

If it ain't fixed, don't break it!............

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06/02/2017 8:35 pm  

Katie_Bush said

"Box 1" looks to me as though it might have been converted for use as a TV sound receiver?

My thoughts ran along those lines too

Crusty's Collection Blogs

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07/02/2017 7:37 pm  

The knob on the front of Malc's telebox varies the audio level- although why it was added I don't know. (I wonder if Malc made any progress with the Rediffusion Mk10 b&w cable set I passed to him...)

Around 1989/90 the market was flooded with surplus teleboxes- both wooden and plastic- much to the delight of 405-line enthusiasts, as Television magazine ran an article on converting them into a VHF modulator. In fact you needed two boxes for the project, raiding them each for a single can module; one for sound, one for vision. The remainder of the telebox went in the bin!  I used mine with a ropey old Pye Lynx vidicon camera to make an optical standards converter. On a good day the results were quite acceptable and provided me with a somewhat elaborate source of signals for the few 405 sets I had. Happy days!

Honestly we'd have killed for something like the Aurora back then!!


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Posts: 4605
07/02/2017 9:40 pm  

Chris said

Katie_Bush said
"Box 1" looks to me as though it might have been converted for use as a TV sound receiver?

My thoughts ran along those lines too  

Not uncommon; it was one in a long line of safe ways to put TV sound through your hi-fi rather than the poor speaker in your TV. I might have some contemporary ads suggesting the same lurking in the boot of the car!

Estimable Member Registered
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Posts: 187
07/02/2017 10:22 pm  

I remember Rediffusion cable TV and those converter boxes from when I lived in Bristol in the late 1970s-1980s. For those not familiar with the Rediffusion system, I'll explain a little about it. You'll then understand why there was a volume control added to some of these teleboxes ...

The cable network consisted of a multi-core cable which carried the sound and vision signals separately.In Bristol, Rediffusion carried BBC1, BBC2 and HTV West (local ITV station) as well as several radio stations, including BBC Radio Bristol. There were no commercial radio stations in Bristol until Radio West started in 1981 - and Rediffusion didn't carry it.

At the customer's house, a rotary switch was installed on the wall or window sill. This selected the pair(s) of wires that carried the wanted radio or TV programme. The audio signals from the cable were powerful enough to drive a speaker directly via a transformer without any amplification. Inside the Rediffusion cable TV set, there's no audio amp, just a speaker with transformer (powered by the cable network) and volume control. TV or radio sound was available with the TV switched off.

In the old days, Rediffusion used to supply radio programmes only. The customer got a box with a loudspeaker and volume control, powered by the cable network. There was no amplifier or valves inside the box. The Rediffusion customer could have radio programmes even if their home didn't have electricity. Of course, by the 1980s this was a quaint old fashoned idea, but the cable system had not changed much in decades and still worked in a similar way.

In 1982 a big change happened when Channel 4 started. Rediffusion was only equipped for 3 TV channels, so customers were supplied with a converter box (the one you have) and a UHF aerial to receive Channel 4. In fact, all the terrestrial channels could be received through the UHF aerial this way. Previously, people had subscribed to Rediffusion because of difficulty receiving terrestrial TV. But by the 1980s, an improved network of UHF transmitters had made Rediffusion cable TV largely redundant.

The Rediffusion company was split up in the 1980s. The TV rental business was sold to Granada, and the cable TV ended up being bought by Robert Maxwell, owner of the Mirror newspaper. The cable service stopped carrying terrestrial TV and radio and offered premium subscription TV channels like Prem1ere Movies instead. The special cable TV sets were no longer made. Instead, the cable customer was provided with an RF modulator 'brick' on the wall that converted the former Rediffusion cable signals into standard UHF. The customer could use this with a standard TV or for the first time, a video recorder - not previously possible with Rediffusion cable.

As the old Rediffusion TVs were replaced, large numbers of the redundant converter boxes appeared on the surplus electronics market. Companies like Display Electronics and Manor Supplies(?) used to advertise them in electronics magazines. The boxes were modified for UHF input to composite video and audio out, and were sold for converting computer monitors into television receivers - hence the name "Telebox". I'm pretty sure "Translator" was the official Rediffusion term for them, but they became known as Teleboxes after the demise of Rediffusion and the subsequent adverts for modified boxes sold to convert monitors into televisions.

Since many computer video monitors had no built-in speakers or amplifier, the ex-Rediffusion boxes were often modified with a volume control and loudspeaker fitted inside. This was easy to do, as the box already had an audio amplifier, essential for driving the speaker in the Rediffusion TV set. That explains the modified box you now have.

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11/02/2017 7:58 pm  
Update: See if the box produces a signal without hooking up to the CH2213


This afternoon I got 'Box two' up onto the bench, the first thing to do was free the tuner as it was seized. After a lot of fiddling and trying to figure out how it worked, success, channels could now be changed without jamming and importantly now one can be selected and tuned.

Now time to feed in a grey-scale from the PM5518T to the Frequency Translators RF input. I hooked up the scope to the base of TR1, nearest easy access was R20. Looks like this box is possibly a good one.



Crusty's Collection Blogs

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09/11/2018 8:41 pm  

I remember my school briefly had a Telebox 2 so the CUB monitors normally used with their BBC Micros could be used to watch schools programmes on in the classrooms rather than us all troop to the TV room.  I guess this version would have converted to RGB.

It didn't work very well, not helped by the ariel in the classroom having poor reception.

Instead the school bought a Sharp 14 inch TV that could be carried about easily.


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