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Old 15th Apr 2017, 9:55 am   #1
Colourstar
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Default BRC950 Hot wire!

Whilst cleaning the contacts in the VHF tuner in my Ultra Bermuda 6632 (BRC 950 chassis) by pure chance I happened to notice the plastic sheathed wiring to the scan coils that is attached to tags just behind the PL500 was blackened and partially melted due to resting against the hot line output valve. Needless to say had these high voltage wires shorted out the results would have been rather unpleasant to say the least. I had to cut back the burnt section and re-make the connections. A timely reminder to watch that any vulnerable leads are dressed well away from sources of heat, especially if they have been disturbed during servicing.

Steve
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Old 15th Apr 2017, 10:15 am   #2
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Default Re: BRC950 Hot wire!

That was very common with the 900/950 Steve. Fortunately both wires are at much the same potential. I can't remember many problems but had to scrape off the burnt plastic wires from the glass tubular PL500/504 on many occasions. I can't recall an actual fire or sparking. John.
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Old 18th Apr 2017, 7:57 pm   #3
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Default Re: BRC950 Hot wire!

That's a lovely looking set Steve, and a great picture too.
David
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Old 18th Apr 2017, 11:20 pm   #4
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Default Re: BRC950 Hot wire!

Hi Steve, when I was a little kid our Ferguson was viewed on a table just like yours. I have it here now. Handy rack below for the Radio Times.
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Old 19th Apr 2017, 7:31 am   #5
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Default Re: BRC950 Hot wire!

The 950 chassis. Another feather in the hat for Thorn. John.
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Old 19th Apr 2017, 11:53 am   #6
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Default Re: BRC950 Hot wire!

Hi Steve,

There's something about that table I recognise
It does suit the telly well though doesn't it
Nice save re the dodgy wires.

Marc.
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Old 20th Apr 2017, 5:32 pm   #7
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Default Re: BRC950 Hot wire!

Quote:
Originally Posted by Heatercathodeshort View Post
That was very common with the 900/950 Steve. Fortunately both wires are at much the same potential. I can't remember many problems but had to scrape off the burnt plastic wires from the glass tubular PL500/504 on many occasions. I can't recall an actual fire or sparking. John.
What's the difference between the PL500 and the PL504 line output valve?
Motorola was big on using the PL500 in the early 60's, even in the 23" sets.
Those sets ran on 140 volts B+ and reasonable performers.
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Old 20th Apr 2017, 8:20 pm   #8
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Default Re: BRC950 Hot wire!

I think it is more robust. The original colour line output valve was a PL505 and this was uprated to the PL509. J.
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Old 20th Apr 2017, 9:53 pm   #9
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Default Re: BRC950 Hot wire!

The PL500 was designed by Philips and is a development of the beam tetrode. The anode is constructed into an assembly called "cavitrap". The function of the cavitrap anode is to capture secondary emission electrons.
According to the Radiomuseum the first valve to employ a similar type of anode was in 1932 and was the type 48 power tetrode. Like the PL500 the anode chambers were designed to capture secondary emissions.
The first UK made set to employ the PL500 was the Sobell ST196. Late 1962?
More information from the Radiomuseum: http://www.radiomuseum.org//tubes/tube_pl500.html

DFWB.

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Old 20th Apr 2017, 9:56 pm   #10
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Default Re: BRC950 Hot wire!

Attachment shows the cavitrap anode employed in the PL500 and PL504.

DFWB.
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Old 22nd Apr 2017, 7:25 am   #11
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Default Re: BRC950 Hot wire!

Not the best of pictures taken with an instamatic camera but the receiver on the right may seem familiar. John.
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Old 22nd Apr 2017, 2:14 pm   #12
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Default Re: BRC950 Hot wire!

Quote:
Originally Posted by Heatercathodeshort View Post
I think it is more robust. The original colour line output valve was a PL505 and this was uprated to the PL509. J.
And the PL 519 was even more uprated...

Wasn't the PL 505 (and 509) intended for 90 degrees sets and 519 for 110?
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Old 22nd Apr 2017, 2:27 pm   #13
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Default Re: BRC950 Hot wire!

Belated thanks for the kind comments further up the thread. The Ultra is currently my main 'daily driver' sitting in pride of place on a period tv table with a selection of 60s magazines beneath. The odd item on top of the set is a very tasteful pottery leaping salmon with- get this- a built in room thermometer. Every home should have one.

That's a great period snap there, John. That Ultra must have been brand new at the time. The pvc implosion guard seems to discolour over the years and on my set the screen looks distinctly yellow compared to my other 60s tvs. Any idea where the photos was taken? It looks like there are some older sets on display too. And is that a giant light bulb at the top of the picture?

Steve
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Old 22nd Apr 2017, 2:58 pm   #14
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Default Re: BRC950 Hot wire!

That's my kind of living room , Steve ... great set - up ! I have the ubiquitous coloured glass fish atop my HMV ( thorn 1500 ) set, as well as a table lamp, with a Bush SRP31C record player nestled underneath. Another thing you can't do with a modern flat thing ( spew ! retch !)
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Old 22nd Apr 2017, 5:48 pm   #15
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Default Re: BRC950 Hot wire!

Quote:
Originally Posted by Colourstar View Post
Any idea where the photos was taken? It looks like there are some older sets on display too. And is that a giant light bulb at the top of the picture?Steve
I wonder.... John.
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Old 22nd Apr 2017, 8:06 pm   #16
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Default Re: BRC950 Hot wire!

Oh! Could it be a certain highly regarded retailer in the Colliers Wood area?
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Old 22nd Apr 2017, 8:09 pm   #17
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Default Re: BRC950 Hot wire!

Possibly. J.
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Old 26th Apr 2017, 6:44 pm   #18
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Default Re: BRC950 Hot wire!

'Reconditioned corner. 1969/70.' I was 21 years old. Some interesting receivers and a few quite old models. A Guaranteed TV for £10. The bed sit lads loved them! J.
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Old 26th Apr 2017, 6:54 pm   #19
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Default Re: BRC950 Hot wire!

Lovely! Even better with a quick tweak. Hope you don't mind
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Old 26th Apr 2017, 8:44 pm   #20
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Default Re: BRC950 Hot wire!

Wow! What a lovely picture. Look at the shine on those cabinets! They may have been at the budget end of the market, but you can tell there's been some time and effort spent on them. Inexpensive maybe but cheap never!

Sadly I think I can identify all of them...

Steve
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