Another big CRT 405 line TV set.

[FERNSEH]

A follow up to the topic about the special Murphy 24" TV we dicussed last month here is another big screen CRT TV set, the mighty KB "Regina" model PV100. This set employs the Brimar C24KM CRT and the chassis is a modification of that used in the 17" model OV30. The EHT voltage is rather low for such a large tube being only 16.5KV. I'm told that the picture was not very good, not as bright as it should be.
I've never seen one, anyone on the forum come across one?
Production carried on to 1960. Two cabinet styles were made. The one shown in the attachment has the appearance of a big "New Queen" model OV30. The other resembled the style of the Pye CW17, a box style cabinet and like the CW17 with a slope at the rear of the cabinet top. Thanks to HKS for this information.
Mullard did make or market a 90 degree CRT which was similar to the C24KM, the AW61-61. Rediffusion used it in a special schools set.

Also, it is possible in the late '50s Masteradio made a 24" TV.

DFWB.

[Heatercathodeshort]

Hello David,
I had two customers with the 24" KB models. The PV100/PV100/1 I believe was the first one looking much like the OV30 New Queen with the plain box cabinet.
It was indeed a poor performer with insufficient EHT for such a large tube. It stuggled to produce enough and any increase in brightness tended to over strain the line output stage resulting in a slight reduction of width and even less EHT. Not one of KB's best receivers, more an Old Queen than a New Queen.
The later model was the QV100 with a much smarter high gloss cabinet that sloped down at the back rather like the PYE CW17 series. My customer had a screw hook in the wall and a similar one at the top of the KB cabinet connected with a length of twine as it was front heavy and tended to feel unstable when changing channels. The picture was only slightly better. These could have been spectacular receivers had a little more care gone into the design. A typical example of a good British product spoilt by cost cutting.
You really need to get over this Nastyradio obsession David. It can only end in tears..John.

[FERNSEH]

Hi John,
In January 1960 Kolster-Brandes issued a service manual supplement for the QV100.
The preface of the supplement states: "this receiver is electrically identical to the PV100/1 with the exception of an improved turret tuner. Mechanically, the receiver is housed in a completely new design of cabinet which is of the consolette type". The "improved" tuner employed the PCC84 which was by 1960 considered a bit dated. By 1960 the PCC89 was well established as the preferred type for current production. Also, the 50CD6G was retained as the line output valve. The R19 EHT rectifier in the original PV100 was replaced by a Mazda U26.
The vari-mu 9D7 replaced a 6BW7 in the common IF amplifier. Better AGC performance.
I do believe a QV100/1 was made which remained in production well into 1961.
The tuner was replaced by a type which used the PCC89.
The Brimar C24KM has a pentode gun assembly which leads me to believe it was in fact a Mullard/Philips MW61-80.
http://www.radiomuseum.org/tubes/tube_mw61-80.html

DFWB.

[Heatercathodeshort]

Yes David, The top heavy one was a consolette with short stubby legs. The tube weighed a ton! I broke the earlier PV100 up when the customer became tired of it. Oh well, we all did it. John

[FERNSEH]

A follow up to the big mono CRT theme. In the 1961 Telefunken pocket data book we find a 24" 110 degree deflection angle CRT. Like all the other 110* tubes the AW61-88 has the 28.5mm diameter neck and the B8H base. Depth of the AW61-88 is 400mm (15 3/4 inches)

Never used in a UK made TV?

DFWB.

[Synchrodyne]

Would that 24 inch tube have been of the “squared-off” type (as described at the time), and so homologous with the then-relatively new 23 inch and 19 inch types of the era, or was it an extension of the older, more rounded 21 and 17 inch types.

Here in NZ the start of regular TV broadcasting more-or-less corresponded with the availability of the squared-off 23 inch tubes, and this I think was by far the majority choice in the early years, with 19 inch a very distant second. But I vaguely recall there were a handful of odd early models that were different, some I think with 21 inch and/or 70 degree tubes, and rarely, 24-inch models that an even vaguer recollection suggests were somewhat rounded rather than being squared off. Around the mid-1960s there were some mentions of 25 inch tubes; if real (and that is debatable), I suspect that that dimension would have corresponded with an American development.

Cheers,

[Heatercathodeshort]

These large metal cone tubes [16" +] were usually presented as the 'Double D' format giving the largest possible picture area. The photo of the large screen Murphy appears to show it as masked exacly like their 12" and 15" models in the conventional way.
The first 110 degree tubes, 17" and 21" [AW43-88] had very rounded corners to reduce the stress in the vulnerable corner areas thus reducing the risk of implosion.
In practise, no risk was involved and within a year the 'squared off' tubes became available in 19" and 23" sizes. Typical numbers being the Mullard [Philips] AW59-90.
The final development became the FST tube of 1984 introduced by TOSHIBA. The 'Flat Square Tube' produced a CRT that was almost flat faced with very squared off corners. It also gave one of the best colour pictures with 100% easily obtained convergence. John.

[FERNSEH]

The AW61-88 was among the group of the 110* CRTs which like the AW43-88 and AW53-88 had the spherical faceplate.
Information about the squared up faceplate 23" AW59-90 can be found in the 1961 Telefunken data book.
The 23SP4 is an American 23" square corner CRT appeared in some UK made sets late 1960. The Pye V600A for example.

DFWB.