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Old 22nd May 2018, 11:58 pm   #21
Philips210
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Default Re: Ultra 6823 (Thorn 1500 chassis)

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1969 to 1977 was a long production run. There can't have been many other chassis that endured for that long.
Hi Nick.

The Philips G8 had a similarly long production run from 1970 to 1977.

Regards
Symon.
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Old 23rd May 2018, 9:03 am   #22
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Default Re: Ultra 6823 (Thorn 1500 chassis)

Yes looking back I was 'playing' around with lethal receivers at the age of 12!

I remember Mum didn't mind if they had small screens, she thought the voltage was lower. Ha! Ha! I was wheeling home Pye D16Ts with mains derived EHT and similar living room sub stations from jumble sales, but even then I was aware of the dangers.
I'm not sure if Dad had been alive I would have got away with it.

The 1500 must have been the longest production run of all time closely followed by the 1400 dual standard chassis. I can remember 20" and 24" very late versions of this but cannot remember the final year of production. They had smaller VHF channel selector and fine tuner knobs. John.
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Old 23rd May 2018, 10:29 am   #23
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Default Re: Ultra 6823 (Thorn 1500 chassis)

This Ultra 6823 1500 was one of the last I sold. The only replacement was the mains dropper, without doubt the easiest to replace of all time.

It had been very well looked after by the customer and I was presented with it when they purchased a new colour receiver.

Very good picture here taken in the living room in spite of very bright sun through orange curtains.

The 20" Mullard tube fitted to a number of these chassis and many more makes, did not retain the expected Mullard sparkle and good emission for long. Examination of these tubes always shows an expired getter, little more than a stain on the neck. The getter itself was a tiny ring affair.

This one is fitted with a Mazda A50-120WR 'Gold Star' and is bright and clear. Early Gold Star tubes fitted in the 900 series in particular, suffered from an internal O/C cathode connection. Infuriating!

Thank you Thorn for producing a television repair man's dream! John.
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Old 24th May 2018, 12:20 am   #24
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Default Re: Ultra 6823 (Thorn 1500 chassis)

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Originally Posted by Heatercathodeshort View Post
Yes looking back I was 'playing' around with lethal receivers at the age of 12!

I remember Mum didn't mind if they had small screens, she thought the voltage was lower. Ha! Ha! I was wheeling home Pye D16Ts with mains derived EHT and similar living room sub stations from jumble sales, but even then I was aware of the dangers.
I'm not sure if Dad had been alive I would have got away with it.
Hi john,
Many thanks for the photo's of your 6823. I'm sure all the ones I encountered in my youth had red PCB's, so I was rather surprised that this one had a green one!
Looking back at my childhood, I am amazed (and very grateful for) the freedom I was given by my parents to play with all things electrical from a very young age. I'm sure mum had no idea of the potential dangers but dad certainly did as electronics was a bit of a hobby for him.
At least in the early '80's, TV's with mains derived EHT were few and far between and none came my way. However, I was unaware of such things as isolating transformers or RCD's.
What I find more surprising though, is that the school exercised no restraint. Mind you, I never actually asked if I could play with their TV's, I just sort of commandeered a bench at the back of a class room and got stuck in!

Bearing in mind I have not seen a 1500 since the mid '80's, I was not expecting much based on everything I had read. Firstly I was surprised to find a Mullard tube and secondly that it had excellent emission.
The picture (apart from dreadful black level) is really good and very sharp even at the edges. Given that it has a valve line output stage, the linearity is also excellent and a blank raster is very 'clean':- no noise, swirly patterns or timebase 'rings'.
Thorn were obviously conscious of the 'serviceability' of their sets and took pity on the poor serviceman stuck in a dingy corner of a living room with dogs and kids crowding round!!
I guess Thorn's crowning glory was the 'jellypot' LOPT. Surely this must have been the most reliable design from that era?
I have great respect for Thorn as a manufacturer and am gradually acquiring sets that were significant to me at the time. Namely the 1400, 1500, 2000, 4000, 9000, 9600, TX9 & TX10.

All the best
Nick
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Old 24th May 2018, 2:58 pm   #25
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Default Re: Ultra 6823 (Thorn 1500 chassis)

Hi
Of course Thorn did make transistorised large-screen mono sets - firstly the 1600 17" with the horrible frame stage, then the 1615 series with more conventional circuitry. This retained the familiar big dropper at the top and used an unreliable LOPT - a first for Thorn after the Jellypots. As many will know, the Eastern European CRT left much to be desired, as did the varicap tuning buttons, but the big problem was a dry joint on the linearity coil, This, coupled with the plastic cabinet, resulted in many fires and caused Radio Rentals to recall and crush them, replacing them, ironically, with the 1500. That's why they are quite rare now.
The last 1500 I remember was a 6 way sloping button 24" varicap set with slider controls, available in white or woodgrain. I have one of each and must get round to getting them sorted. Being 1500s, there won't be much wrong with them!
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Old 9th Jun 2018, 10:42 am   #26
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Default Re: Ultra 6823 (Thorn 1500 chassis)

Thanks to 'Dazzlevision', I now have the correct slider controls for the brightness & volume. This was almost a drop in replacement assembly- even the cableform & plug was the same. However, the plastic moulding was slightly different so I had to unsolder everything and swap the controls to my one.
All done now and working well. The controls are nice and smooth and didn't even need a squirt! And, no, the plastic lugs didn't fall off either!

Examining various capacitors reveals date codes of about the middle of 1977. The boost diode and 30FL2 are 'TCE' branded both with '77 date codes so are probably originals.
They must have moved away from the black 'Callins' electrolytics by then as most of them are blue 'Rubicon' types. I've always found these to be very reliable and none need changing in this set.

It could do with a new PCL805 as it takes a while to achieve full frame scan. I've got a brand new one somewhere!

So that just leaves the black level clamp mods to build properly and that will be it. As the picture is so good, the set will see regular use for watching old programmes.

All the best
Nick
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Old 9th Jun 2018, 11:04 am   #27
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Default Re: Ultra 6823 (Thorn 1500 chassis)

I think part of the 1500's charm is how a narrow picture appears and then fills the screen as its warming up. My auntie's Rediffusion also did the same.
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Old 9th Jun 2018, 10:07 pm   #28
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Default Re: Ultra 6823 (Thorn 1500 chassis)

Yes, this artefact was an instant indication which sets used a tripler rather than the more usual EHT rectifier valve, resulting in the picture appearing dull and oversized, shrinking to normal as the valve reached full emission.

Alan.
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Old 30th Jun 2018, 3:47 pm   #29
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Default Re: Ultra 6823 (Thorn 1500 chassis)

The Ultra in John's photo has curiously long legs !
I first bought an Ultra 1500 like yours when I was 20 back in 1995 and it was my only set for the next 18 years, the only trouble being some SOV and when the tripler went in an acrid puff...
I now have an identical ex rental Ultra in much better operational condition , as well as it's HMV badged brother with the lovely teak cabinet currently as my daily driver. One thing i've noticed is how the pictures emerge on warm up, the Ultra comes on with a squashed picture that fills top and bottom, the HMV a narrow picture that fills east and west. I suppose how they are set up has some bearing on this...or do they all have their own personality ?
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Old 30th Jun 2018, 11:07 pm   #30
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Default Re: Ultra 6823 (Thorn 1500 chassis)

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Originally Posted by AnalogueMatty View Post
One thing I've noticed is how the pictures emerge on warm up, the Ultra comes on with a squashed picture that fills top and bottom, the HMV a narrow picture that fills east and west. I suppose how they are set up has some bearing on this...or do they all have their own personality ?
I think it's probably got more to do with the emission of the line O/P and frame output valves. I found that with new valves the picture would only take a few seconds to get to the right size, but with tired valves anything up to 5 mins!

Cheers
Nick
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