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Beau Decca mirror lid TV set.
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April 6, 2017
6:20 pm
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Till Eulenspiegel
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The control panel has been completed. The value of the variable resistors differs from those originally fitted for the old Plessey chassis.   The control functions are, from left to right:  line linearity, line hold, contrast, frame hold, height and frame linearity.    The width control is now located on the line output transformer case.   No sync control required for the Plessey Mark 1 chassis.   This leaves two blank holes which might be used for the line and shift controls.  But let's get this thing going before such refinements are added.

The next stage of the Beau Decca TV chassis reconstruction will be the modifications to the power supply unit.  The 5KV EHT transformer must be removed and the 2volts CRT heater transformer fitted instead.

 

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April 8, 2017
5:01 pm
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Till Eulenspiegel
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The EHT transformer has been removed from the Beau Decca power supply unit and refitted in the Defiant TV PSU. Pictures show before and after the transformer transplant.BeauDecca2PSU.jpgImage Enlarger

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The Beau Decca uses a pair of PX4 triodes in the output stage, I still have these having resisted the temptation of selling them to an Audiophool for hundreds of pounds.  I also have a pair of Mullard PM24M directly heated output pentodes, the final and much more powerful version of the PM24 series.  Triode connected the PM24M might possibly be a viable replacement for the PX4.  Just thinking why not treat the Defiant to a push-pull out stage? 

Till Eulenspeigel.

April 8, 2017
5:07 pm
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PYE625
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Till Eulenspiegel said

The Beau Decca uses a pair of PX4 triodes in the output stage, I still have these having resisted the temptation of selling them to an Audiophool for hundreds of pounds. 

Jolly good because once they are gone, they are gone.

You can't get audio by stuffing the pound notes in the valve bases.  grin_gif

Andrew, a Fenland fanatic.                                                                                     

                         

April 8, 2017
8:37 pm
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Till Eulenspiegel
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  I don't think there are any PX4s still being made by the Chinese or Russian valve makers.   As well as Marconi-Osram there was a number of other manufactures that made a power triode similar to the PX4. Most well known was the Mullard ACO44.  

Till Eulenspiegel.

April 20, 2017
6:23 pm
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A 2volt CRT heater transformer replaces the original 5KV EHT transformer which has now been transferred to the Defiant TR1247 power pack.   Unlike the previous arrangement the CRT heater will be switched off when the Beau Decca is switched to radio.    The finned metal rectifier seen on the left of the picture is for the negative grid bias supply for the PX4 audio output triodes.

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April 20, 2017
9:27 pm
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Brian Cuff
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It's quite funny, Till. You have reconstructed the TV chassis for your Beau Decca and I have done the same for the PSU/Audio chassis for my Beau Decca.  Maybe at some time we should get together!!

Cheers

Brian

April 21, 2017
9:42 am
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Hi Brian,    We know of three Beau Decca TVs have been got at in one way or another. I remember the late Gerry Welles constructed a TV chassis for a Beau Decca, he adopted the Viewmaster design for his set.  I'm sure that set appeared in an Ebay auction not so long ago.   My set had been converted into a radiogram.  The reason why I chose the Plessey Mark 1 circuit was for two reasons. First it is easy to construct and the parts were to hand, and secondly John Wakely mentioned that in the 1970s he saw a Beau Decca in a junk shop in Croydon and that set was equipped with the Plessey Mark 1 chassis.  Your set was relieved of it's power and audio amplifier chassis, actually I'm surprised more Beau Decca TVs haven't gone the way as the RGD 1046 radiogram. Many 1046 radiograms were chopped up just to retrieve the excellent audio amplifier.

Till Eulenspiegel.

May 22, 2017
6:10 pm
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That's the main chassis assembly is completed so now I must summons up the courage to try it out in the Beau Decca cabinet.

The Cossor sourced RF unit was tested some time ago and found to be OK. We know the timebases work but before power unit is connected up it might be wise just to check that there are no wiring errors. 

The attachment shows the now very busy underside of the main chassis.

 

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