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Old 20th May 2018, 7:53 am   #9
Nuvistor
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Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,427
Default Re: Ultra 6823 (Thorn 1500 chassis)

Quote:
Originally Posted by 1100 man View Post
Yet another interesting comment suggesting that customers didn't like black level clamping! That has cropped up several times from people in the trade at the time. Maybe, then, it was more of an active decision by manufacturers not to clamp the black level as they found customers didn't like it?

When was the 1500 released and when did it cease production? Thorn were experienced with all transistor TV's, and so on the face of it, continuing to use valves in the output stages was a retrograde step.
The black level clamp did cause some problems but I didn’t have any sets returned because of it and when CTV came along those were clamped. The 1500 chassis like most of Thorns output was made for rental and keeping costs down was the order of the day. Black level clamping was not a necessity.

I think the 1500 chassis was introduced for the start of the 3 stations transmitting on UHF 625 in November 1969 or thereabouts. We didn’t sell many but I think they were still in production in the middle 70’s, not many other large screen BW sets available then. They had poorer quality CRT’s in some of the late sets, same with the valves, not a criticism of Thorn, had to get what was available.

I think they kept using the design because it was proven and low volume any major BW redesign would take resources from other R&D so I can understand them running this chassis as long as possible.

I didn’t see many 1500 sets but like all Thorn large screen BW sets they were easy to fix.
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