Thorn TX10 - did they ever fit RCA S4 CRTs in it?

[Maarten]

The S4 tube may have been the most licensed tube worldwide. In Europe it or similar tubes were made in Italy, Germany (East and West), Poland, Czechoslovakia and maybe others. The licensing was sometimes from RCA, other times from Toshiba apparently. Maybe the RCA license ran out and Toshiba took over? Or Toshiba made some subtle changes in construction?

Videocolor and ITT called it the PIL-S4 which sometimes lead to some joking, as pils is the Dutch word for lager (beer).

[MALC SCOTT]

Rediffusion MK3 sets used RCA tubes in the 22/26 inch sets. The 20 inch versions used an Hitach crt, later the same tubes were Finvalvo. These tubes lasted forever, unlike the RCA types.

[Welsh Anorak]

Hi
Thanks Malc - those 20" 110-degree in-line CRTs were excellent. I only ever had one fail when some clumsy oaf (hi!) knocked the neck off one. I remember the purple labels and often wondered where they came from - Finland, I assume?
I just wished they fitted into Philps KT3s - no such luck!
Glyn

[Leon Crampin]

The Rediffusion Mk 3 used a different in-line tube from the S4. Branded RCA, it used a toroidal scanning yoke and needed a wholly unpleasant SCR line output stage to drive it. A horrible set to work on - hence the S4 and the development of the Mk 4 chassis.

Leon.

[FERNSEH]

As a follow to the TX10 30AX CRT questions: Did the designers consider the 20" 30AX CRT? The 110degree A51-540X did exist I believe. Can anyone recall any sets that used it?
Dare I mention the Ferguson 51K5? This 21" set employed a S4 110 degree CRT. Some 21" ICC5 used 90 degree CRTs.
Also, was the TX10 designed exclusively for 110 degree CRTs?

DFWB.

[Philips210]

I have never seen an A51 540X 20" 30AX tube used in any UK Television, though it must have been possible to make one. There was of course an A51 500X or A51 510X 20AX tube with 110 degree deflection as used in say a RBM T20.

I always thought the TX10 was purely for 110 degree 22" and 26" tubes. The TX9 was for 14", 16" and 20" 90 degree tubes. All of these Thorn sets were a pleasure to work on. I found the TX10 MK2 a better engineered chassis compared to the later TX100 series. The TX10 seemed an easier set for working on and repair. It was all downhill when the Thomson ICC5 came along.

Regards
Symon

[dazzlevision]

Originally Posted by FERNSEH

As a follow to the TX10 30AX CRT questions: Did the designers consider the 20" 30AX CRT? The 110degree A51-540X did exist I believe. Can anyone recall any sets that used it?

Dare I mention the Ferguson 51K5? This 21" set employed a S4 110 degree CRT. Some 21" ICC5 used 90 degree CRTs.
Also, was the TX10 designed exclusively for 110 degree CRTs?

DFWB.

Hello,

I have never seen the 20" 30AX CRT in any British designed and built set, although perhaps Rank Radio International may have produced 20" models fitted with their 30AX chassis, which was known as the T26 (IIRC).....? I've never come across an RRI set with this chassis. It was certainly used by B&O in their 20" 5500, 5502 (30AX chassis) models; I have a 5502 in my collection.

As for a TX10 fitted with a 90 degree CRT, I very much doubt it. All 20" Thorn CTVs in the TX10 era were fitted with the TX9 chassis.

Regards,

Dazzlevision

[Studio263]

Originally Posted by Welsh Anorak

They also claimed a large video bandwidth, partly from mounting the RGB transistors on the CRT base - maybe this was a first?

Not really, the Japanese had been putting them there for years! The Sony KV-1340UB springs to mind as one example, I'm sure there were others. Thorn may have been the first to put a green LED on the tube base though, whatever it was for...

Here is a full list of B&O models that use the 20" 30AX:

Basic: Beovision 5000, 5002
Basic remote: 5100, 5102
Full spec. remote: 5500, 5502

Nice sets all, the 5502 is one of my favourites. Shame that there was no room for the 20" 30AX in the MX2000 / M20, instead we got the Nordmende ICC3000 chassis and an odd Toshiba tube that gave funny colours. The later Videocolor one was better but it didn't last. Still, worse was to come with the ICC5-based MX3000, I've never seen a good tube in one of those. They also did a couple of models with the 20" 20AX, the Beovision 3000 (no, not THAT Beovision 3000) being one. These were odd sets, they looked like the 30AX ones but they had the 20AX chassis inside. Seldom seen here.

[Philips210]

Originally Posted by dazzlevision

perhaps Rank Radio International may have produced 20" models fitted with their 30AX chassis, which was known as the T26 (IIRC).....?

Hi.

Of the few T26 based sets that I serviced, they used either 22" or 26" 30AX tubes. I think the 20" sets in RBM/RRI range after the T20 would have used the excellent Toshiba T24 chassis with it's outstanding reliability.

Regards
Symon.

[Red to black]

I have never seen a 20" TX10, and I don't believe a 90 degree tube was ever fitted to one, as you say the TX9 was used for that role.

One thing though, if you have a look at either the MK1 or 2 main PCB (metal chassis), there is a resistor or link silk screened on the PCB marked with two positions 90 and 110 degrees, obviously the component is fitted in the 110 position, but the option is marked.

So maybe the designers originally considered this as an option, ala TX100 at one time ?

For those decrying the ICC5 , that chassis has more in common with the TX10 than most others the way the PSU topology is arranged.

[FERNSEH]

I'll have to dig out the write up about the TX10 when in early 1980 the the then all new chassis was announced in "Scope" which was the tech bulletin issued to Ferguson dealers. Later Scope became "Feedback"
I'm sure there was a mention to the fact the chassis was designed to drive all types of CRTs including those with 90 degree deflection angles.

DFWB.

[Red to black]

I wouldn't mind a copy of that article David, if you find it.

It is possible they were considering a "core" chassis as in what the later TX100 became, capable of driving more CRT types.

The TX10 chassis was relatively large though, where as the TX100 was of similar dimensions (and shape) to the TX9.

[Red to black]

RE: 90/110 "link"

For anyone interested, the actual component is R730 on the metal chassis version (I don't have a diagram for the MK3 plastic version), this is a 1 ohm thick film resistor in the feed for the 150V HT line.

It is not actually marked as 90/110 on these diagrams, but is silk screened on the actual PCB, anyway in the 90 degree position it would actually connect to a different (lower) tapping on the EHT/Chopper transformer, giving a lower HT presumably., more suitable to driving a 90 degree tube.

Unfortunately I no longer have any scrap chassis for these sets, so I cannot post a picture of an actual PCB, maybe someone on the forum has.

I have included the drawings of both the component and the copper sides of this PCB with the component ringed (and the alternative position).

[dazzlevision]

Hello,

The TX10 manual, part one, section A, does state that "...the chassis is capable of driving 110 degree CRTs in screen sizes from 20" to 26". No mention of 90 degree CRTs.

I have looked through TCE "Scopes" for the relevant period and can find no reference to the TX10 driving 90 degree CRTs. However, as Red to Blacks says, the earlier TX10 PCBs did have a ref to 90 degrees.

Regards,

Daz