TV sets with 3 core (Earthed) cable.

[hillwalker]

Good Evening all,

Although it is accepted that ALL TVs (of course I am referring to CRT sets) have 2 core mains lead only, since the casing etc is double insulated e.g plastic, woodgrain etc, I am fairly sure I once came across a Monochrome portable set with a 3 core lead on it.
The set was given to me with a load of junk about 25-30 years ago, although it failed to work.
I kept it for about a couple of years but then threw it away, but prior to doing so I opened the back cover and there was a fair amount of metalwork within one side (left hand side when looking inside with back cover removed) of the (all plastic) casing.
I cannot however, recall exactly where all three conductors were connected inside the set. The set was probably from the 1970s, certainly no later than early 80s but probably not earlier than the 70s since colour coding was brown, blue and green/yellow.

Has anybody else ever come across this?

(I am fully aware that older TVs produced often employed a 'Live Chassis' arrangement with the Neutral made to the internal chassis metalwork, but of course this arrangement only required a two core mains lead as (virtually) always.

Regards

[Bobdger]

Redifussion mk4 had a 3 core mains lead with the main earthing point by the mains sw which was then connected to the chassis. Many years ago about 1976 I serviced some BRC 1500 sets that were fitted with an mains transformer the chassis was earthed. These were in a amusement arcade. Bob

[Nickthedentist]

So did Sony KV2212 & 2215 I think.

[thermionic]

There was also the ‘Teleton’ colour portable TV of the early 1970’s which had an all metal cabinet surround with a wood grain finish. This had a 3 core mains lead.

This set had an American look to it, but was manufactured in Japan.

Cheers. SimonT.

[dazzlevision]

The original Philips dual standard T-Vette (405 & 625) portable mono TV had a three pole mains connector, as did the 17” Pye Rambler, fitted with the hybrid single standard 169 mono chassis.

[Restoration73]

A few even pre-date the above ;
Ekco TMB272
Pye PTV

[Peter.N.]

Nearly all sets had 3 core cable in the '40s and early '50s as they had mains transformers, when real mass production started they were all AC/DC so you couldn't earth them. Even if they were connected up the right way round you could still have voltage between neutral and earth.

Peter

[AJSmith625]

The Sony TV9-90UB had a 3 core mains lead, but as it was late 1960s I can't remember if it was the old colour wire code or the new. The OP says the main chassis mostly occupied the left hand side of the set looking from the rear. This would fit in with the 9-90.

Alan.

[davidh1041]

The amazing BRC 2000, the worlds first colour tv, very expensive looking mains transformer inside

[greg_simons]

Originally Posted by davidh1041

The amazing BRC 2000, the worlds first colour tv, very expensive looking mains transformer inside

Yes indeed, the brilliant brc2k, fully earthed chassis and a whopping mains tx.
Greg

[Graham G3ZVT]

Originally Posted by davidh1041

The amazing BRC 2000, the worlds first colour tv

Well, arguably the first solid-state production CTV

[AC/HL]

Excluding the CRT, mandatory then, it was. A typo on David's part I think.

[Vintage Engr]

There were quite a number of colour T.V's with 3 core mains leads, and even a real double-wound mains transformer, i.e. not an SMPS PSU, but a linear one.

Most of these domestic TV's were around prior to the SCART socket era, and many had BNC composite video inputs as well. Mitsubishi and Hitachi were among the manufacturers.

In the Broadcast/industrial T.V. area that I worked, sets like this meant that we could have a source of relatively low-cost monitors available. This helped to keep install costs down, where the use of a grade 1 monitor, such as those from Pro-west, Cintel, or Croma wasn't required.

David.

[dragonser]

Hi,
I can remember a late 1950's or 1960's tv that had a metal case that was earthed but I think had a ac dc arrangement for the power supply. I think it was 405 line only... ? so the chassis was live !
But my Memory isn't as good as I would like it to be, so I can't remember anything else

[1100 man]

Originally Posted by davidh1041

The amazing BRC 2000, the worlds first (all transistor) colour tv, very expensive looking mains transformer inside

Yes, that must have added considerable expense to an already very expensive set! It certainly adds to the weight!!

Strangely, it also uses the thinnest 3 core flex I've ever seen!

I've also got a Dynatron TV32 21" 405 set that has a massive chassis with an equally massive mains transformer. No idea why they did that as there are no external inputs. There is also a high valve count so standard AC/DC practice with droppers would have been fine.

Mains transformers were expensive and so only tended to be fitted to British TV's for special purposes such as external inputs on monitors or 'schools' sets.

Cheers
Nick

[its ur aerial]

I think the reason why Rediffusion MK4`s were built as a class 1 appliance, was that they were extensively used as monitors in commercial and industrial sites, including the Palace of Westminster, used there for displaying messages to Lords and MP`s.

Ken G6HZG

[Peter.N.]

I had forgotten about the BRC 2000, a very advanced set indeed, I was still working on hybrids. In the '50s English Electric made sets with the top half of the cabinet being metal and a metal cone CRT with EHT over the whole outside surface, of the flared part anyway, they just covered it in polythene.

Peter

[Leon Crampin]

As an ex employee, I can confirm that the Rediffusion Mk 4 and 4A chassis were fully isolated and earthed via the mains lead. This was indeed done to facilitate external inputs, but came as a bonus with the Siemens free running switch mode power supply which was, in its day very efficient.

Combined with a narrow neck Videocolor (sic.) tube, these sets ran reliably cool with a power consumption of about 60W. A good British designed and manufactured set.

Leon.

[Richard_FM]

I did wonder how the Rediffusion cable connectors worked with a non-isolated chassis, or were the earlier sets also isolated?

[hillwalker]

Originally Posted by AJSmith625

The Sony TV9-90UB had a 3 core mains lead, but as it was late 1960s I can't remember if it was the old colour wire code or the new. The OP says the main chassis mostly occupied the left hand side of the set looking from the rear. This would fit in with the 9-90.

Alan.

Good Evening

If I remember rightly, looking inside with the back cover removed, the main PCB with LOPT etc was the usual flat type (designed to pull out) laid directly below the CRT, whilst looking towards the left inside the cabinet, was some metalwork (albeit a single piece) which I think some of it covered the front end of the set where the volume knob, loudspeaker and on/off switch were situated.

Regards