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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.

 

Till Eulenspiegel.175228.jpgImage Enlarger

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April 8, 2017
5:01 pm
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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

BeauDecca3PSU.jpgImage Enlarger

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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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.                                                                                   

                         

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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June 10, 2017
6:10 pm
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Well, here goes. But first I’ll play safe and use the variac to supply power to this set.  Installation of the receiver chassis is impeded by the gram pre-amplifier, the thing with the red EF37 valve, so that unit will be repositioned to the right of it’s present position.  The CRT anode connector is positioned to be close to the power pack, if the CRT has to come out for any reason it will be reinstalled 180 degrees around so that the anode connector will be closer to the receiver chassis. There is a possibility that the original scanning coils, (the ones that were removed from the Defiant TR1247) will not match the Plessey Mark 1 scanning components, if that is the case then the CRT will have to come out. The whole CRT support assembly was made in the 1990s and was copied from another working Beau Decca set. 

Till Eulenspiegel.BeauDeccaChassis.jpgImage Enlarger

June 11, 2017
10:16 am
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Fingers crossed – or – as the Germans say “Thumbs pressed”, Till.

Cheers

Brian

June 11, 2017
2:46 pm
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Hi Brian,    auf Deutsch:   daumen drucken?    Nicht wahr?  Can’t  do umlaut u on this laptop.  No number pad.

Till Eulenspiegel.

June 12, 2017
7:47 pm
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Today the Beau Decca was connected to the mains, no bangs or flashes.  Function selector switched to the TV position. All of the valves are lit up.  The push-pull PX4 audio amplifier is working, however, that’s all. No HT supply is reaching the new TV receiver unit. The 6L18 triode audio amplifier on the TV chassis should be active on all services, that is, TV, radio and gram input.  The  280 volt HT supply should be present for the audio amplifier irrespective of the input selector position.  It’s likely there is a wiring error in the power unit.

Till Eulenspiegel. 

June 12, 2017
7:56 pm
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It’s on it’s way to working, following the thread with lots of interest.

Frank

June 12, 2017
10:58 pm
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Hi Frank,

           It’s good news. The missing HT supply fault has been found and I’m gratified with some results, a nice bright raster. There’s too much hum though, most likely the HT electrolytics need replacing.  The HT voltage supplied to the sound and vision chassis is 280 volts, that’s about 20 more than the regular Plessey Mark 1 chassis.

Must supply the set with some 405 line TV signals.

 

Till Eulenspiegel.

BeauDecca130225.jpgImage Enlarger

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June 13, 2017
1:21 pm
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The hum coming from the loudspeaker originates from the frame timebase. When the volume control is turned down the hum disappears.   

The Mazda UU8 HT rectifier valve has failed and as I have don’t have a spare a pair of BY127 silicon diodes will be used instead. Each diode will have a 50ohm series resistor for surge protection and also to compensate for much lower forward voltage drop across the diodes.

Till Eulenspiegel.

June 13, 2017
6:14 pm
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Taking no more chances with Mazda UU8 rectifier valves and instead I’ve opted for the solid state solution to the problem. Two  BY127 silicon diodes and series resistors have been fitted on tag strips and the whole assembly simply plugs in the existing valve socket.   What this set needs is more short circuit protection so in due course fuses will be wired in the mains input and HT supplies.

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June 14, 2017
7:50 pm
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Results of today work on the receiver chassis. The set is now displaying a bright stable test card.  Still a few jobs to do both electrical and mechanical.

Till Eulenspiegel.BeauDecca_first_picture..jpgImage Enlarger

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June 14, 2017
9:33 pm
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Another success for you David. thumb_gif

Frank

June 14, 2017
9:46 pm
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Till Eulenspiegel said
 The set is now displaying a bright stable test card.  Still a few jobs to do both electrical and mechanical.

  

 And very well done too….. Take a glass or two of your favourite tipple in celebration cheers

Andrew.                                                                                   

                         

June 14, 2017
10:01 pm
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Maybe a bottle of Black Sheep ale tonight. Only one though, Doctor’s orders.

https://www.blacksheepbrewery.com/

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