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Forum 135

[Closed] Beau Decca Mirror-lid TV/Radio - spot the theft.

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Marc
 Marc
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Perhaps I should go to a model shop and get some of the power pylons for a model railway to rum my speaker cables over to stop me getting coloured sound what ever that is :aak
The alternative if you are being a cheapskate it plastic drawing pins :aak

Tut tut, you can't do that, the pin is the wrong colour !
It's red for right and blue for left :aak
And don't do it the other way round or you'll be back to front :aaj

Marc.

Marc
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RSGB call sign 2E0VTN

 
Posted : 01/02/2014 1:37 am
Katie Bush
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What a load of cobblers! £900! I suppose when you're prepared to pay £180 for an IEC mains lead and £35 for a 5A fuse, £900 is quite cheap for something so old!

Or £100 for a set of four bamboo "Panda Feet" to keep your oxygen free speaker cables off the floor!

Marion

 
Posted : 01/02/2014 1:46 am
Anonymous
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Tut tut, you can't do that, the pin is the wrong colour !
It's red for right and blue for left

I'm sure though in the 1970s at least BBC used Red for Left and Blue for Right. We had an ink rubber to polish the GPO jacks if we got bored. The cable was coloured rather than Plug.
(Red lefties and True Blue Conservatives)

The domestic stuff though is Red Right and bLue Left. Except when it's Black & White coloured RCA. Are they consistent?

 
Posted : 01/02/2014 1:56 am
Refugee
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Model railway pylons will work much better because you will be left with the money to pay for the power to run the amplifier :aaj
They would hate the covers on my amplifiers and it is there fault that I keep them firmly screwed on to protect the valves.
I will keep the covers dove grey to prevent the sound being coloured though :aak

 
Posted : 01/02/2014 2:10 am
Till Eulenspiegel
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The push-pull amplifier in the Beau Decca TV set produced only 5watts. The amplifier in the record reproducer version is capable of 12 - 15 watts. Same output triodes, PX4.
Finding a replacement for the PX4: It is agreed a the triode connected 6L6 has the same characteristics as the PX4, the problem is that the pentode has a 6.3 volt heater. The directly heated triode has a four volt filament, so we need an easy to find and cheap replacement with a four volt heater. How about the Mazda PEN45? There is plenty published information about this valve operating in it's normal role as a beam tetrode but I can't find any info about the valve as a triode. One is sure, the ra will be low when triode connected. The operating conditions of the Mullard AL60/CV9 should be studied.

http://www.radiomuseum.org/tubes/tube_al60.html

Till Eulenspiegel.

 
Posted : 01/02/2014 2:14 am
Till Eulenspiegel
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One serious drawback with the substitute valves suggested in my previous post is the heater current.
The PEN45 takes 1.7 amps. The PX4 takes only one amp filament current.

Till Eulenspiegel.

 
Posted : 01/02/2014 2:23 am
Refugee
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In some cases there might be room to add some more turns to the mains transformer and use 6 volt valves.

 
Posted : 01/02/2014 2:30 am
peterscott
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I'm sure though in the 1970s at least BBC used Red for Left and Blue for Right.

Should really be red and green as in shipping and of course port is red.

Peter :cca

www.nostalgiatech.co.uk

 
Posted : 01/02/2014 11:49 am
Anonymous
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How I was taught when learning to sail age 8
Red: Port = Larboard so Left (Port is grape based and such drinks can be red)
Green thus Right and Starboard.

 
Posted : 01/02/2014 12:03 pm
peterscott
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Hi Brian,

If this one has also been asset stripped then the buyer might part with the amplifier chassis.
http://www.ebay.co.uk/itm/Vintage-Beau- ... 7675.l2557

Peter

www.nostalgiatech.co.uk

 
Posted : 01/02/2014 2:08 pm
Till Eulenspiegel
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Two pictures of the power unit in my Beau Decca. Sans PX4s. Don't know what's happened to them. Perhaps some audiophools sneaked into the shop and pinched them.

Till Eulenspiegel.

 
Posted : 01/02/2014 2:35 pm
Refugee
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The bidding looks awfully high :cch

 
Posted : 01/02/2014 2:36 pm
Brian Cuff
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Thanks for the pictures, Till. Now I know what I'm up against.
Actually, It doesn't look too bad to reproduce, at least compared to the BT8161. I'll be able to take measurements etc. when I've picked the loner up from Harpy.

I can see the EHT rectifier, the HT rectifier, the phase splitter and the O/P triodes but what's the other valve with a top cap? I've just had a good look at the pictures and it's not a valve so I assume that it's an EHT smoothing block - 2 x 0.1mfd perhaps! The empty IO sockets are for the interconnect leads, I assume. But there are two top cap connectors 1 = CRT, 2 = ?? Or is it a "double ender" to connect a spigot on the cap with the final anode spigot on the CRT?

How's this as a classic example of thinking aloud (or allowed) :aaj :aaj

Forum Memorial

 
Posted : 01/02/2014 2:56 pm
Cathovisor
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I'm sure though in the 1970s at least BBC used Red for Left and Blue for Right. We had an ink rubber to polish the GPO jacks if we got bored. The cable was coloured rather than Plug.
(Red lefties and True Blue Conservatives)

The domestic stuff though is Red Right and bLue Left. Except when it's Black & White coloured RCA. Are they consistent?

There's no consistency in the domestic market. Mostly red/white (and I remember red/yellow being common), but my Dual CS505 is black (left) and white (right). At one time PO double-enders were blue and red to differentiate between shielded and unshielded cables - IIRC the blue ones were unshielded, the red ones shielded. Later ones all seemed to be shielded which was essential when plugging up a microphone point, else how else did the 'phantom' get down the cable?! But as far as I recall, the nautical colouring for PPM needles has always been the case in the BBC. PPMs are even subject to a British Standard...

 
Posted : 01/02/2014 2:57 pm
Cathovisor
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It is agreed a the triode connected 6L6 has the same characteristics as the PX4

Now, according to Williamson*, the KT66 has identical characteristics, triode strapped, as a PX25. This may also explain why some late-production Decolas have an unused 6.3V winding on the power transformer...

*D.T.N. Williamson - from here.

 
Posted : 01/02/2014 3:01 pm
Brian Cuff
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The blue ones were the shielded ones IIRC!

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Posted : 01/02/2014 3:02 pm
Till Eulenspiegel
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Hi Brian,
the valve line up in my Beau Decca TV power supplier is: audio amplifier 6SN7GT and 2 X PX4. The HT rectifier is a Mazda UU8. EHT rect. Mazda U22. The single 0.1mfd EHT smoothing capacitor has a Bulgin valve top cap fitted for safety. Direct connection to the CRT anode.
Bias for the PX4s is supplied from a separate SenTerCel rectifier, the finned component at the right side of the chassis picture.

Till Eulenspiegel.

 
Posted : 01/02/2014 5:15 pm
Till Eulenspiegel
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There was an article in a 1998 Radiophile magazine about the PX4. It tells us how the valve started out in 1929 as a very modest 1.1 watt triode. In it's earliest form the filament current was 0.6 amp, the gm 3.3, amplification factor 5.5 and the ra 1,060 ohms. Amplification factor = gm X ra.
Intended as a successor to the LS3 and LS5 triodes the original PX4 was made for battery or mains use.
In it's final form the PX4 has a maximum anode rating of 15 watts. Va max 300V. Filament current is 1 amp.

Till Eulenspiegel.

 
Posted : 01/02/2014 11:38 pm
IJK2008
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Hi Brian

These classic sets just seem to seek you out?

Look forward to more of the story as it unfolds.

Ian

 
Posted : 01/02/2014 11:44 pm
Till Eulenspiegel
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I mentioned earlier that the TV chassis in my Beau Decca came from a Defiant 12" console TV which was made in 1947/8. It is agreed that there are many Beau Decca TVs in existence but I know of only one other Defiant TV1247.
So this begs the question. If or when I get around to making a replacement chassis for the Defiant should I fit it into the rarer Defiant or install it the Decca and return the other set to it's original state?

Till Eulenspiegel.

 
Posted : 13/02/2014 10:36 pm
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