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B&W TV Did HMV ever use this circuit in the UK?

Black & White Television

Last Post by irob2345 1 year ago

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irob2345

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Back in 1957 a brilliant Oz engineer by the name of Neville Thiele (of Thiele-Small parameters fame) designed this circuit while he was working for EMI TV production division at Homebush, a suburb of Sydney. It continued on with minor tweaks until the end of valve TV production.

The neat thing about it is that it doesn't need a linearity control, although some versions do have one to keep the twiddlers happy.

I may have mentioned this previously, but until today I didn't know it was designed by the Great Man himself!

Oh yes - a 6GV8 is an ECL85, the 6 volt heater version of the PCL85.

It precursors the use of current feedback that was almost universally used in solid state designs.

Posted : 14/09/2023 10:31 am

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TV in the 50s

Till Eulenspiegel

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Seen nothing like that in a UK made HMV TV set.

The attachment shows the circuit diagram of the frame timebase in the very last EMI made TV set, the model 1854. it's a very simple circuit which employs the PCL83 triode-pentode, a valve I believe that was never used outside the UK.

All subsequent HMV and Marconi TVs were made by Thorn Electrical Industries.

Till Eulenspiegel.

Posted : 14/09/2023 12:34 pm

irob2345

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The PCL83 appeared in the very first model EKCO TV sold here. The ECL83, aka 6AB8, also appeared in the EKCO TX275 portable (I have one of these).

I've also seen the 6AB8 used in a car radio (a long time ago).

It also made an appearance in about 1950 in a very simple 2 / 3 valve superhet published by Radio and Hobbies magazine. The triode was used as a regenerative IF / detector. Worked quite well, apparently.

As far as I am aware, Neville Thiele's excellent circuit wasn't used by anyone else here. Patents?

As a TV tech in the early days it always puzzled me how it worked, i.e. why they needed that extra transformer. It was only after I learned more I really appreciated how clever it was.

Posted : 15/09/2023 9:21 am

irob2345

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The 6GV8 was widely used here. There is an interesting back story about this valve.

Kriesler used to use them in TVs but they had problems with loss of V sync during warm-up, causing the TV line at Caringbah (not Alice St Newtown as is commonly believed, that factory burned down in 1958) to reject a large percentage of them.

When Philips refused to replace them under warranty, Kriesler were stuck with them.

What to do? Put them in a mantle radio!

So the 11-99 was born.

https://www.radiomuseum.org/r/kriesler_11_99.html

Inside that modern looking ABS case with its fold-down handle was a metal chassis, a mains transformer, 3 or 4 valves (later builds had a silicon diode rectifier) and point to point wiring. And, in early production, Ducon wax paper caps, using up old stock!

The small line that built them employed older workers that couldn't handle PCBs or solid state. Kriesler was that sort of company.

The 11-99 was the last valve mantle radio in production anywhere in the world. And they sold tens of thousands of them!

Go into any antique shop in Australia and you will probably find one.

Bet it still works, too! I've never seen one that doesn't.

Posted : 15/09/2023 9:50 am

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