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Dual Standard Decca mono TV.

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Till Eulenspiegel
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I've won this attractive Decca dual standard TV on Ebay. I've no idea which chassis it has, it could be the all metal one that sits on the cabinet floor or the not so nice double deck chassis. We'll just have to wait and see. The set is located in Gateshead so it can't be far from my place.

Till Eulenspiegel.

 
Posted : 16/03/2014 11:17 pm
Marc
 Marc
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Hi Till,

Very nice ! Both myself and Steve (Colourstar) were discussing that set over a cup of tea and a slice of cake yesterday, lovely looking beast and going to a good home too 

Marc.

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Posted : 16/03/2014 11:22 pm
Till Eulenspiegel
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Hi Marc,
I'd guess this set is of 1965/6 vintage. The rotary tuning control is for VHF 405 and the push-buttons are for UHF. Looks like a Rimband 1 CRT. Likely to be an A59-11W.
Don't think it is the metal dual standard chassis. We'll soon find out.

Till Eulenspiegel.

 
Posted : 17/03/2014 12:16 am
Focus Diode
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Not long ago there was a thread on the UKVRR forum regarding the rarity of Decca B&W d/s models. I've yet to see one. A wonderful find and couldn't have gone to a better home. Very much looking forward to seeing it.

Cheers,
Brian

 
Posted : 17/03/2014 12:09 pm
Till Eulenspiegel
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I'm off to Gateshead this afternoon to collect the set. Standby for a new TV topic.

Till Eulenspiegel.

 
Posted : 17/03/2014 12:41 pm
malcscott
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I am looking forward to seeing it working later today! 

 
Posted : 17/03/2014 12:49 pm
Till Eulenspiegel
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Hi Malc,
I never thought it would come to this, me buying a dual standard TV set.

Till Eulenspiegel.

 
Posted : 17/03/2014 12:57 pm
malcscott
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Hi David, i thought it was a bit too modern for you!

 
Posted : 17/03/2014 1:00 pm
Till Eulenspiegel
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1966? modern times for me.

Till Eulenspiegel.

 
Posted : 17/03/2014 1:09 pm
Till Eulenspiegel
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The set is in the van waiting to be unloaded, I'll need help with this one, it's mighty heavy, so heavy in fact that' I would not have attempted to lift it even in glory days when I was super strong.
About the set: it has the Decca double deck chassis that resembles the BRC 850. The push button UHF tuner has valves. Information can be found in the 1965/66 Red Radio and Television servicing book as the Decca DR1.
The CRT is a Mazda CME2305, rimband 1. I'd reckon this will be an easy set to get going, the only evidence of any servicing is a mains dropper section and the PCL82 sound output valve has been replaced sometime in the seventies, it's got the "new" Mullard trademark.
The set is designated as the DR123. The cabinet is in very good condition and all it needs is a good clean up.
Standby for more news.

Till Eulenspiegel.

 
Posted : 17/03/2014 5:37 pm
crustytv
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I was looking at the service data last night and wondered if it was this chassis, however I thought it looked like a 19", shows how photos are deceiving.

I have the Trader sheet (1729) service data for this set if you want it uploaded to the library.

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Posted : 17/03/2014 6:01 pm
malcscott
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Is this the model with the plug in loptx?

 
Posted : 17/03/2014 6:10 pm
crustytv
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Yes

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Posted : 17/03/2014 6:12 pm
Cathovisor
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One of the TVs in my 'wants list' - the RGD 519 - has a double-deck chassis like that, but 405 only.

 
Posted : 17/03/2014 7:21 pm
Till Eulenspiegel
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The Decca is now in the workshop. First observations showed me that the HT fuse is missing, also the HT sections of the mains dropper have been bridged with a pair of 15 ohms resistors. This raises suspicions that there is something amiss in the HT circuits. Read on.
The set was powered up in the traditional HKS method, just plug it in. The heaters lit up, crackling noises from the loudspeaker, all very encouraging, then the 1 amp HT failed. An HT short? Worse than that, the line output transformer has a short circuit to ground. Reference to the attached circuit diagram. The earthed upper winding has shorted to the main winding. I'm sure that this earthed winding has no function in the line output stage, it simply feeds a blanking pulse to the CRT first anode. I'm hoping that it will be possible to isolate this winding. I'll dismantle the transformer and add extra insulation to prevent any possibility of breakdown to the ferrite core.
There is evidence that the set has never been used on 625 lines. The Telefunken UHF tuner has the original valves, PC86 and PC88. It's well known that those valves were never reliable.
The VHF tuner is a Philips AT7629/22. Date of manufacture of this set is confirmed as mid to late 1965.

Till Eulenspiegel.

 
Posted : 17/03/2014 9:38 pm
FRANK.C
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Hi David
Would inserting a capacitor between the earthy end of that winding and earth be enough to isolate it?

Frank

www.electronics.frankcuffe.ovh

 
Posted : 17/03/2014 10:15 pm
Till Eulenspiegel
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Hi David
Would inserting a capacitor between the earthy end of that winding and earth be enough to isolate it?

Frank

Hi Frank,
I considered that but there is a possibility that high peak voltages exist between the main winding and the earthed winding. Might be better to isolate it completely. I'll address the line flyback blanking in another manner later. Reference to the second picture. The offending winding is indicated by the arrows.

Till Eulenspiegel

 
Posted : 17/03/2014 10:31 pm
ntscuser
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There is evidence that the set has never been used on 625 lines.

I suspect that was a very common occurrence as it meant paying for a new aerial to receive a channel which was of little interest to many people and which transmitted for only very limited number of hours each evening.

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Posted : 17/03/2014 10:46 pm
Refugee
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There are three bobbins there.
What bobbin is the winding actually wound onto?

 
Posted : 17/03/2014 10:53 pm
Till Eulenspiegel
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The EHT winding shares one limb of the transformer core with a retuning winding for 625 lines, it doesn't appear on the original circuit diagram. The other winding, on left side of the picture, is the main auto transformer and the extra flyback blanking winding is wound on the same bobbin. It's likely the two windings are close wound together at the boost HT end. Probably that's why the insulation failed.

Till Eulenspiegel.

 
Posted : 17/03/2014 11:10 pm
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