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Old 7th Jan 2004, 2:18 am   #1
Hybrid tellies
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Default Favourite Colour Televisions.

Continuing on from discussions started in " Ethical Dilemma " which had moved on to peoples preferances regarding early colour tv's.
First I nominate the Decca Bradford chassis. Which gave excellant pictures and good sound. This set was also very engineer friendly and a dream to work on. And my old CTV1910 mk1 still gives the new Philips colour set in the lounge a good run for its money.
My second choice is the ITT/KB CVC5-8. These were a panel changers nightmare with its single swing down large chassis. The pictures were always superb with pin sharp definition. The sound not as natural as the Decca was more than adequate. Servicing these sets was like the Decca a pure joy. Despite the bright clear pictures the tubes lasted for ever. In all my time I have ever known one tube to be changed, but this was a mistake by the engineer as the fault was proved to a beam limiting fault.
The B&O 2600 or 3000 probably produced the very best of pictures, with lots of brightness and contrast plus great EHT stabilization but like the Philips G6 and K70 were very complex beasties and a nightmare to work on. They ran very hot and after say 30 mins I am sure you could fry an egg on top of the cabinet over the line stage.
The G8 is my final choice. Great picture and sound and quite reasonable to work on. The G8 definatley being the best of its era in the first generation of all transisterised colour chassis. Yes the BRC3000 could give good pictures for a while after setting them up but they did drift out of adjustment very quickly due to the high operating temperatures of this set.
Finally on the CDA verses RGB drive I would definatley say that cathode drive is best. My main experiance with CDA drive was on the Pye 691/693/697 chassis with its banding, constantly varying colours poor definition plus the bad burn ups. But I am quite prepared to admitt that most of the problems were down to pure bad design. We had a saying that the only good Pye was a Philips..
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Old 7th Jan 2004, 1:20 pm   #2
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Default Re: Favourite Colour tv's

Oh yes the scorched Pyes and burning Bushes. I think someone redesgned the Pye cathode drivers with a plug in solid state circuit which got rid of the problem.

I agree with you about CDA drive. A well set up G6 with a 90 degree tube and quite lethal but very stable eht stabilisation was quite superb.

yes agree ITT CVC5 tubes seem to last for ever and i liked the small Decca Bradfords which just seem to have a liitle bit of focus pot and tripler trouble.

I dont think G8s are that suitable for today's enviroment
(computers. phones etc) that old thyristor use to get quite grumpy and sends lots of old cackle down the mains line.





 
Old 7th Jan 2004, 1:50 pm   #3
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Default Re: Favourite Colour tv's

I remember those B&O sets and they certainly produced the best pictures I have seen in a domestic colour receiver. As you say the EHT stabilisation was excellent; on flashing " Top of the Pops " pictures, whilst most set's pictures were leaping about all over the place, the picture on the B&O was rock solid. They also produced excellent definition and convergence. The convergence circuits were particularly complex. My first colour TV was a 25 " Philips G6 which gave very nice pictures.

When set manufactures stopped using the RCA shadow mask CRT design, although light output improved, definition always suffered. Subjectively, in my view, the best post RCA pictures came from Sony Trinitrons in models such as the KV2000UB.

Picture quality in most new colour TV is very poor due to the search for low prices. One of the most common problems with new large screen sets is poor purity. This is due to the fact that modern CRTs do not have magnetic screening, which brings down the cost of CRT manufacture considerably.

Going back to 405 monochrome, I think the Pye VT4 picture quality was one of the best. Any comments?
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Old 7th Jan 2004, 2:35 pm   #4
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Default Re: Favourite Colour tv's

I forgot to mention that the BRC2000 (see the Ethical Dilemma thread) had fully regulated EHT, generated separately from the line scan. When average brightness changed the picture always stayed rock solid. That's probably another reason why the beeb converted some to monitors.
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Old 7th Jan 2004, 3:05 pm   #5
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Default Re: Favourite Colour tv's

I have a soft spot for the G8, as it was easy to fix, though the last one I had seemed to eat Chroma panels.......

Jim.
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Old 7th Jan 2004, 4:16 pm   #6
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Default Re: Favourite Colour tv's

One of the early B&O hybrids, twin line output valves, is here, but suffered a small internal burn-up before arrival and I've yet to assess the damage, never mind evaluate its performance. Currently I'm using a 1983 model 8802, which had quite a gathering of dry joints on its i.f. board (at least five responsible for various intermittencies) but is performing gratifyingly now.
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Old 7th Jan 2004, 6:41 pm   #7
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Default Re: Favourite Colour tv's

I'm sure most (UK) people know by now, the Decca Bradford was so named because it would have been the next Baird (made in Bradford) had not the designer gone to Decca and taken his design with him. It was a straightforward set to work on, but watch your fingers on the sharp chassis parts!
I also have a soft spot for the 2000. I was given one many years ago, and had many happy hours getting it to work well and (cover your ears those of a nervous disposition) converting it to SS working. I disposed of it when the tube failed for about the fourth time, something I now regret.
My first memory of colour was of seeing a GEC DS hybrid in the early days when most people still had mono. Cracking picture, but I can't remember the sound.
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Old 7th Jan 2004, 6:58 pm   #8
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Default Re: Favourite Colour tv's

Don't worry, I converted my 2000s to 625 only too. Helped reliability. I replace the tube in 1 of them when I had 11V on the heaters and the red was still awful. I put a 26 " push through tube in a 25 " cabinet. Took a little carpentry. The old yoke and the new tube were absolute pigs to purify and converge. Pincushion correction may have been optional on the old 25 " tube; it was essential on the flatter, squarer 26 " .

I seem to remember that in the 3000 they avoided having pincusion correction by mounting the tube upside down and relying on the angle you viewed the set from.
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Old 7th Jan 2004, 7:33 pm   #9
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Default Re: Favourite Colour tv's

Quote:
Picture quality in most new colour TV is very poor due to the search for low prices. One of the most common problems with new large screen sets is poor purity. This is due to the fact that modern CRTs do not have magnetic screening, which brings down the cost of CRT manufacture considerably.
Sony sets are good in this regard. Our 28 " widescreen " WEGA " (flat-fronted) Sony set has excellent colour purity (if the whole screen is supposed to be the same colour it IS the same colour. Linearity is very good too, except on the " Panoramic " modes where they deliberately skew it. Reliability is good so far (2 years) too, compared to our previous Panasonic which had a shot tube after 18 months.

Sorry - drifting off-topic again.....
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Old 7th Jan 2004, 10:34 pm   #10
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Default Re: Favourite Colour tv's

Quote:
Sony sets are good in this regard. Our 28 " wide screen " WEGA " (flat-fronted) Sony set has excellent colour purity (if the whole screen is supposed to be the same colour it IS the same colour. Linearity is very good too, except on the " Panoramic " modes where they deliberately skew it.
The picture geometry on my Fathers Sony Wega is dire! I though they were all like that I've limited experience of modern TV's my most up-to-date is a Solara J chassis (Granada badged) that I hooked off the dump at the back of the 80s. It had visible fly back problem that was due simply to a bad connection between chassis and the tube base. If I find something worth watching on TV I may udgrade

I guess to adjust the geometry on a modern Sony you need to know how to enter " engineering mode " and fiddle with the handset!
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Old 7th Jan 2004, 10:58 pm   #11
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Default Re: Favourite Colour tv's

Yes, with modern tellies it's all done from the handset in engineering mode. I have no idea how to get into engineering mode on a modern Sony, but someone with the relevant information may be along in due course!

I haven't plugged a cross-hatch or anything into our Sony to check the linearity, but on most modes things like rolling credits stay the same size as they move up the screen. On panoramic mode (and maybe one other) it is deliberately squashed at the top and bottom, so that people in the middle of the screen don't look as fat due to the fitting of a 4:3 picture on a 16:9 screen!

If you want poor linearity, go and take a look at the Hitachi widescreen sets in Currys!
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Old 7th Jan 2004, 11:09 pm   #12
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Default Re: Favourite Colour tv's

we have some large (36 " ) Sony monitors at work, where the scan waveform is produced by a microprocessor controlled DAC. They come with a Sony supplied handset, which allows you to display an internally generated crosshatch, and move from dot to dot around the screen, correcting the convergence and linearity about every 0.25 " . A well practised man can set one up in a day, it takes the rest of us about 2.5 days...... We have approximatly 60 of these in continous 24hr service, plus spares and engineering displays (call it 75), and they have to be checked at least once year!

Sony have declared that they are no longer going to support these units, so as a special favour to us, they let us do a lifetime buy of spre tubes (about another five years worth) at a discount price of 50% off - the tubes were still £11000 each, and no there isn't an extra zereo on that!

The only special thing about thse monitors is ther size, other wise they are fairly normal high resolution RGB units.

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Old 8th Jan 2004, 2:55 am   #13
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Default Re: Favourite Colour tv's

Hi, thanks AC/HL the history of the Decca Bradford is a fascinating storey. All to do with the Thorn take over of the Radio Rentals Baird factory at Bradford. The end result was a superb blend of technology between Decca and the excellant Baird team.

Sydney mentioned possible problems with thyrister power supplies. In Bath in a block of flats some strange goings on with electrics were reported and remained a mystery for some time. The electric clocks in the building were found to be going backwards The problem was traced to a recently repaired BRC8000 where somebody had linked out the mains input choke after it went o/c!

We also used to replace the Pye cda panel with that transisterised thing. The pictures were ok but looked a little flat lacking contrast and definition. But hey this was good for a Pye CT205 Philips did bring out a replacement cda panel which used standoff valve bases.But it was very expensive and to late for most of these Pye chassis as they were either being scrapped or had gone up in flames.

PPP Penguin mentioned that the BRC3000 did not use pin cushion distortion which it did n't and fitted the tube upside down. The later BRC3500 continued to use upside down tubes together with a pin cushion correction cct. This is to cope with the newer flatter tubes such as the A56-120X. My 19 " Decca Bradford also does not use a pin cushion correction cct its all inked out. I actually tried to fit one from parts obtaiined for the 22 " model.But the results were rather strange so I replaced the links again! I learned (the hard way) that all 19 " colour tubes do not require pin cushion correction as these tube were the older more rounded type as compared to the new flatter ones used in 20 " 22 " & 26 " models.

Does anybody remember the RBM A823, there first solid state colour chassis. We had loads of these out on rental. They were very heavy sets with the 22 " models being a two man lift. They were the first to use chips or IC's in the colour decoder. The sound was very good but the pictures always looked a little flat ie there was never quite enough contrast. They suffered many maladies including the BT106 in the power supply. Strange colour faults, line ouptut transister and tripler failure but strangly I cannot remember a single Line output transformer fail. This is hard to believe now considering the problems RBM were having with all the loptx's in all their mono sets. Can anyone else comment on this.

Finally on new sets quite a few friends have bought new widescreen sets all reporting geometry problems. They get a new replacement set and that is either the same or worse. There seems to be a lack of engineers available to sort out any problems. Something else that might help todays trade is for the new widescreen test card to be put out on a spare digital channel on all of the digital platforms. This would help both the engineers (if there are any left), and of course the customer buying these sets.
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Old 8th Jan 2004, 9:59 am   #14
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Default Re: Favourite Colour tv's

The main reason for the CDA panel on the Pye hybrid overheating was grid emission developing in the PCL84s. Cure was to replace grid leaks (2.2m IIRC) with 680k.
A 'solid state' PL802 was also available!
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Old 8th Jan 2004, 11:24 am   #15
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Default Re: Favourite Colour tv's

Yes, I remember the Rank A823 - it used a very strange decoder without a reference oscillator, which was actually very reliable. Never had a LOPTx fail, either. The power supply was very much like the G8.
Decca Bradfords were very reliable, and simple.
GECs did give good results, but that dreadful double-sided print! Aaarrrggghhh!
G6s - the dual standard and first single standard (contrast control on front) were more reliable than the last ones (511/513) and if set up correctly, picture quality was very good.
Not to K70 standard, though. This had flywheel frame sync, so perfect interlace. All supplies were from LOP stage - very advanced for time. There was a PL509 and a PL504 - the latter switched the scan current, so LOPTx had fewer turns-per-volt and thicker wire. Very complex sync-sep stage - 6 transistors. 2 speakers and crossover filter. Low level convergence controls - something like a B & O
Mike

The BRC 9000 was quite good, but not the 8000 - cheap and nasty. You could tell a 9000 being switched on by the sound of the SYCLOPS starting up!

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Old 8th Jan 2004, 10:00 pm   #16
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Default Re: Favourite Colour tv's

I think Baird's loss (after Radio Rentals was taken over by Thorn) was definately Decca's gain - including the sets after the Bradford hybrid series. I believe that the Baird factory in Bradford continued to make Thorn chassis based sets until it was closed. Not long after, Microvitec took it over to make monitors (Microvitec was originally set up by Tony Martinez, previously of Baird/Radio Rentals, Bradford).

The Rank A823 chassis was not in fact the first CTV to use an IC in the decoder. The preceeding 22 " CRT dual standard hybrid sets used on (plessey SL907?) and incorporated pincushion correction. Nice set.

Returning to the Pye hybrids, I used to fit standoff wirewound resistors and valveholders, in order to reduce the PCB temperature. It was only worth doing this if the PCB material was not too darkened (and therefore conductive). The CES/Philips Service replacement CDA panel incorporated these improvements and doubtless lasted longer (it wasn't that expensive either). Although they gave a pretty nice picture (apart from the brightness control being the picture size control in this chassis!), I have one in my collection - a Pye CT72, 22 " - because the cabinet looks so good (in my humble opinion).

The later solid state Pye 725/731/741 series were quite good and they had that most unusual arrangement for the printed panels - all arranged vertically around the CRT, like a fan! Let's not mention the IF screened module with all those dry joints after a couple of years!

Like others have said in this discussion, I reckon that the delta gun, 90 degree shadowmask CRT picture takes some beating (if the chassis that is driving it was a good one).
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Old 8th Jan 2004, 10:26 pm   #17
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Default Re: Favourite Colour tv's

I also remember the A640 as being very reliable. In an age when TV's routinely needed a bit of attention from time to time (if not a fault then a tweak here or there) I remember going to 3 year old examples with all the pre-sets still sealed. One common problem with the later ones with the pre-set chroma level control on the IF board was intermittently going mono. You walked into the house, loosened a couple of back screws, reached in and eased it a few degrees. Up came the colour and you were back in the car before the Customer closed his mouth!
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Old 9th Jan 2004, 1:03 am   #18
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Default Re: Favourite Colour tv's

Hi All

With regard to the Rank A823 chassis, I remember them well. There reliability at first was poor due mainly to the two flyback capacitor in the LOP stage. After trying several " improved " capacitors they finally got them to work reliably with a completely new capacitor design. Another problem early sets suffered from was a tendency for the line to lock out of phase. This gave a picture with a black bar down the middle. The cause was unusual; the set used a flywheel sync system if which there was a coil in a can tuned to line frequency. Pulses radiated by the LOP transformer were picked up by this coil and caused the symptom. Rank later modified the coils so that the ends of the windings were transposed; any stray pulses then picked up were in anti-phase to previously and did not cause a problem. The reliability of these sets was then quite good by the standards of the time.

The company I worked for had hundreds of these sets out on rental and we never had one with LOPTx failure.

Regards

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Old 9th Jan 2004, 2:48 am   #19
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Default Re: Favourite Colour tv's

I agree with what has been said about the old delta gun tube,but they did need a lot of power to drive them.I think it is only recently that the modern tubes have caught up definition wise. In line tubes were always brighter but it is only recently with tubes like Philips Blackline tube that you have got good definition back again.

I think the first colour set I saw was a relations GEC Duel standard set, but the first one that I was impressed by was the Philips K70 which was owned or rented by our neighbors.

Working for Radio rentals for a while in the early 80's we saw plenty of those BRC9000's. What became of syclops?. I always remember these sets,when in trip mode,would make exactly the same sound as our collie dog being sick.
We saw loads of BRC8000/8500 and 8800's. Always suffered poor pictures with lots of streaking. They did not sort this out until the 9800 chassis came out. For some reason Thorn went backwards and used the A56-120X crt and an 8000 like chassis. But it had a brilliant picture. The reason? instead of using the 180v line to feed the RGB output stages on the 9800 they used a boosted HT Line of 250v.This made all the difference.

I have to disagree on the Pye 725/731/741. If the Pye hybrid chassis was bad, these were horrendous and were often trouble from when you took the damm things out of the box. As I said before, my opinion of course,the best Pye was a Philips. I don't think this was always the case but it certainly was with their colour tv's in the 1970's.

Returning to the A823's the guys at RRI tried very hard to iron out the problems with this set and I think succeeded. Like ukcol our company had loads of these out on rental and are customers were very happy with them. There was only 1 fault which could cause alarm when 6c13 which is the A1 supply reservoir or smoothing cap would go s/c causing the feed resister 6r7 to to go up in a huge cloud of smoke.
Now how many of you can remember clearing a power supply fault and after refitting the power supply forgetting to plug in the degause coils. The result is that nearly all the mains voltage ends up across a 1w 680 ohme resister ((8r5). The smoke would fill a room within a few seconds of switch on. I did this once just as the manager walked into the workshop. I saw this shadowy figure through the smog turn tail and walk out making a comment about the cigarette I was smoking
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Old 9th Jan 2004, 9:27 am   #20
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Default Re: Favourite Colour tv's

Yes, I remember the first Rank s/std chassis with the decoder chip - CV2510, IIRC.
BRC 8000/85/88 I hated - lousy picture quality and a habit of eating the BU205 once a week.
Wasn't too impressed with Pye 725, either - very poor EHT regulation, and virtually every one had those dryjointed rivets in IF can.
The smaller Pye (713?) with all the panels in plastic guides stapled to the cabinet was a cheap and nasy thing, as well.
The BRC 9600 was fairly decent and reliable.
I used to like thyristor line OP stages, mainly because no-one else knoe how they worked - the Zanussis and Grundig 5010 / 6010 used these, as did the Grundig portable, whose white cabinet back eventually became brown and crumbly!
The remote control system on the 6010 was a very elegant circuit.
Mike

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