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malcscott
(@malcscott)
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Posts: 1490

Rediffusion had thousands of sets fitted with the A823 chassis. A very  popular one was the RT529/22. In 1979/80 they had a small batch of them refurbished. This included a new light teak coloured cabinet, 6 way varicap tuner and every modification to the decoder/psu/scan drive. Also fitted was a new Mullard Colourex crt. These crt,s were from a small batch from Mullard r+d. From switch on the picture was visible within 3 seconds. Often the degause cycle was visible on the screen. The few that went into service lasted well into the 80,s and were then scrapped. I salvaged a few of the crt,s and fitted them into Philips G8 sets. Never had one go low emmision.    

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Posted : 11/12/2020 10:46 pm
colourmaster
(@colourmaster)
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Posts: 399

Hi Malc, I have a coop A823 with one of those quick heat tubes fitted. It certainly makes a difference.

Regards Gary

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Posted : 13/12/2020 9:59 am
Cathovisor
(@cathovisor)
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Posts: 5789

But for the other faults it had, I really wanted to acquire an A66-410X to replace the A66-140X in my old Telefunken 711-chassis set.

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Posted : 13/12/2020 1:21 pm
Nuvistor
(@nuvistor)
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Posts: 4142

Where there mods to the heater circuit to replace a Mullard Quick heat CRT with a standard type, resistors probably.

I don’t recall the Mullard quick heat CRT’s being that reliable, the cathode heater assembly was much smaller to allow it it heat quickly.

Perhaps I have a false memory but other quick heat CRT’s, were not that great either, Hitachi ones come to mind.

Anyone confirm or put me right on this?

 

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Posted : 13/12/2020 2:05 pm
turretslug
(@turretslug)
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Posts: 522

It can't just be me who finds it a little ironic that several decades of progress means that the screen of a current TV set lights up effectively instantly, but it now takes about a cathode's-heating time for the actual electronics to catch up and work out what it's meant to be doing.

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Posted : 13/12/2020 2:42 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 11259
Posted by: @turretslug

It can't just be me who finds it a little ironic

Nope you're not alone, I started a thread pretty much exactly about the same thing back in June.

https://www.radios-tv.co.uk/community/general-tech-discussion/oh-the-irony/

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Posted : 13/12/2020 3:02 pm
Cathovisor
(@cathovisor)
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Posts: 5789

@turretslug

Sony's swirling balls...? Or just that period where you stand in front of a set you think you've switched on and there's that agonising wait in front of an audience before it boots up and deigns to show a picture.

I do say to people sometimes that we're waiting for the valves to warm up.

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Posted : 13/12/2020 3:43 pm
Katie Bush
(@katie-bush)
Illustrious V-Ratter Moderator
Posts: 5150
Posted by: @cathovisor

........a set you think you've switched on and there's that agonising wait in front of an audience before it boots up and deigns to show a picture.

And in the case of some sets, they take just as long to adjust to a different resolution, eg, my Samsung when switching up from SD to HD, or vice versa. Damnably infuriating, and yet again when switching inputs, say, SKY on an HDMI port, to to the DVD player on a SCART.

On the plus side, and ironically, the start up latency isn't actually too bad on this thing - 3 to 4 seconds, which I find quite acceptable.

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Posted : 13/12/2020 5:00 pm
malcscott
(@malcscott)
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Posts: 1490

@nuvistor There were no mods for the heater cct. Fed direct from mains t/x. As far as i know Mullard never produced a new version of this A56-120X. The ones fitted to the Rediffusion sets were all Mullard Colourex reguns.

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Posted : 13/12/2020 9:54 pm
Nuvistor
(@nuvistor)
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Posts: 4142

@malcscott

Yes the A823 had the heater transformer. 
There were mods to heater circuit if the heater was supplied from the line times base which was the case with the Pye 731 chassis, just found a reference and that would be what I was thinking of. The July 1975 Television magazine, available in the forum library, as an article by Harold Peters on the subject.

 

 

 

 

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Posted : 14/12/2020 12:44 am
malcscott liked
irob2345
(@irob2345)
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Posts: 289

Quick heat tubes need closely controlled heater voltages and so are generally powered from the LOPTx.

Re "warmup" time of flatscreens, it does have to boot the OS you know.

Programming what are known as "bare metal" systems is becoming a lost art. I designed a bare metal embedded web server recently (just the hardware, a colleague did the firmware) and it's ready to go in less than half a second after power on.

Younger programmers these days can only write in high level script languages that need an operating system..

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Posted : 14/12/2020 2:49 am
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