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Old 9th Oct 2007, 8:53 pm   #1
howard
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Default 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

Hello again,

I bought this 1946 Double Decca complete with its box in Belgium some time ago for not a lot. On its box is a label with the name "Fonior" who were Decca importers in Brussells which included Decca records which there had the Fonior label. This example has the attractive caramel/red striped 'air travel' hessian cloth covering on its wooden case and the front panel is a cream painted aluminium pressing with the 'Double Decca 46' name stamped on it so is one of the first Double Deccas built in 1946. The rear panel unfortunately had had a hole cut in it and one of its knobs was broken and the set was sold as not working, its N16 valve described as 'kaput'. During its 2 month long restoration, we found that a lot more in this set was also kaput .... but what is good about it is that its main case is in remarkably good cosmetic condition.

I acquired two more Double Deccas for spares for next to nothing, one full of woodworm and the other dropping to bits. After I bought the second one at Gerry Wells tabletop sale, a collector came up to me and suggested before switching the set on, to place it at the top of the garden at the end of an extension cable and then stand well clear ! It does seem that these Decca sets have a reputation for not being the best in quality, often being referred to as 'Double Trouble's, which made me even more determined to build a really good one !

I did the outer case first, stuck down the odd bit of loose material and then just a quick clean with upholstery cleaner restored its brightly coloured hessian covered case. Colin here very kindly donated a replacement knob and the first scrap set provided a perfect rear panel.

The first scrap set also provided a replacement battery plug and the aluminium cover which fits under the chassis, the original was missing as two large additional German made smoothing capacitors had been fitted by its previous Belgian owner. The mains cable and battery cables were rotten so I bought some new replacement 2 core braided cable here in a selection of colours from PWH and a set of 4 new Osram and Mullard valves from Phil Taylor to replace the original mix of Osram and US valves and I already had a stock of new US sourced axial capacitors to replace its wax capacitors.

I made a start on the chassis, and replaced several wax and one electrolytic capacitors, cleaned the valve mounts, fitted the new valves and then took the set over to Ron Bryan for new mains lead and battery leads to be fitted, which he did, carefully tying the ends with lacing tape. The set was first fired up via its battery leads (90v and 7.5v from two power supplies) and away it went, but it was soft and not at all sensitive. It was then tested via its mains lead after its voltage selector plug was moved from 110v to 240v and again it just about worked but a check on the selenium rectifier revealed an output of only 75 volts and it was getting rather hot. Continuing on battery power, Ron then found another leaky wax capactor hidden on the output transformer, that was replaced and the set then played much louder. Further improvements were made by cleaning the removable aerial's two plugs and sockets which were very tarnished. By now the set was working quite well on all wavebands on battery power, just needing realignment.

Attention was then turned to the mains power, and we decided it would be sensible not to leave the worn selenium rectifier in circuit, but to replace it with a discretely hidden 1N4006 silicon diode and series resistor.
The selenium rectifier was disconnected but left in place, and into existing holes in its two metal mountings were pressed a couple of insulated Oxley barb tags, and between them the silicon diode and series resistor covered in shrink wrap were mounted. The two extra German smoothing capacitors were removed and then the 250 uF filament smoothing capacitor was found to be leaky, so it was removed and Ron took it to a friend with a lathe who expertly cut out the top bung. A new modern capacitor was fitted inside, and the bung replaced and secured with araldite and the repaired cap soldered back in place. The set was then realigned and was now working well.

The valve filaments are wired in series on this set and measurements indicated inconsistences in the filament voltages, three of the valves should have a voltage of 1.4 volts and the twin filament N16 amp valve 2.8 volts but they were all well out. Edward (Igranic) suggested the use of filament shunt resistors to correct the voltages and supplied the circuit diagram for a post war Philco where these were fitted. Similar value resistors were then fitted to all four valves in the Decca and after some trial and error changes the filament voltages were all set spot on ! A new ceramic class Y mains filter capacitor was then discretely fitted (the original left in place but disconnected) and the set then soak tested. Just one further problem occurred when LW stopped working and that was due to a poor earth tag connection where a countersunk screw had been used - that was cleaned up and replaced and the set has since worked perfectly. The chassis was then returned to its case.

The Double Decca in this hessian covered case I think is a very good looking 60 year old portable radio, and there are radios built today which have more than a passing resemblance to its cabinet design. I guess some of its technical shortcomings can be attributed to shortages of components just after WWII, but now this one has been completely overhauled and sorted it will work reliably from now on. And it does work well, picking up everything on MW and LW (although there is a touch of background noise on LW) and with a good aerial it also works well on SW, and it's a pleasure to listen to and to behold.

One last thing, I couldn't decide whether or not to repaint the front panel as it is slightly worn and the paint is slightly flaky in the middle, so please feel free to comment and if more folk vote for a re-spray than to leave it asis then I'll do it.

Howard
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Last edited by howard; 9th Oct 2007 at 9:19 pm.
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Old 9th Oct 2007, 9:05 pm   #2
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

I spotted one of these in the background of a scene from "Murder at the gallop" (with Margret Rutherford as Miss Marple) the other day when it was shown on TCM.
Another splendid job Howard.
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Old 9th Oct 2007, 9:25 pm   #3
Robert Darwent
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

Quote:
Originally Posted by howard View Post
The valve filaments are wired in series on this set and measurements indicated inconsistences in the filament voltages, three of the valves should have a voltage of 1.4 volts and the twin filament N16 amp valve 2.8 volts but they were all well out. Edward (Igranic) suggested the use of filament shunt resistors to correct the voltages and supplied the circuit diagram for a post war Philco where these were fitted. The same value resistors were then fitted to all four valves in the Decca and that did the trick and the filament voltages are now all spot on !
Hello Howard

You've done a really first class restoration there, very well done!

I've two of these sets myself waiting to be restored, and an additional scrap chassis from a third set. One of my Decca's has a dark blue case, the other is the same as your restored set.

I was just wondering if you could give the resistor values that Edward (Igranic) supplied you with please? I would like to add shunt resistors to the valves on my sets too when I start restoring their chassis's.
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Old 9th Oct 2007, 9:28 pm   #4
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

Hello Howard,

That's a very interesting report, especially as I have a DD (not sure which variant) lying around which I intend to play with one day soon.

They're very quirky sets, and I like the unique styling which has a quite "modern retro" look to it - a DD wouldn't exactly stick out like a sore thumb if it were displayed with some of today's radios.

BTW, have you read the interesting article about these by the late Geoffrey Dixon-Nutall in a back issue of the BVWS Bulletin (on the CD)? I can recommend it highly.

Personally, I would re-spray the front, but only if you could do it to a very high standard (which I'm sure you could). An amateurish DIY paint job always looks worse than a battered original one.

Nick.
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Old 9th Oct 2007, 9:33 pm   #5
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

Quote:
Originally Posted by Tim View Post
I spotted one of these in the background of a scene from "Murder at the gallop" (with Margret Rutherford as Miss Marple) the other day when it was shown on TCM. Another splendid job Howard.
Hello Tim,

I just looked up that film and it was made in 1963 so that Double Decca was already a old set then. Someone at the studio obviously liked the look of it though !

Ron Bryan deserves most of the praise for this restoration as he did all the tricky repairs.

Howard
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Old 9th Oct 2007, 9:39 pm   #6
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

Quote:
Originally Posted by rrdmpb View Post
Hello Howard

You've done a really first class restoration there, very well done!

I've two of these sets myself waiting to be restored, and an additional scrap chassis from a third set. One of my Decca's has a dark blue case, the other is the same as your restored set.

I was just wondering if you could give the resistor values that Edward (Igranic) supplied you with please? I would like to add shunt resistors to the valves on my sets too when I start restoring their chassis's.
Hello Robert,

Ive slightly reworded that sentence since you cut it, resistors the same as those in the Philco were used as a starting point but were changed and it was a case of trial and error to get the filament voltages correct on each valve. I will let you know later what the start/end values of the resistors were for each valve.

Howard

Last edited by howard; 9th Oct 2007 at 9:54 pm.
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Old 9th Oct 2007, 9:51 pm   #7
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

Quote:
Originally Posted by Nickthedentist View Post
Hello Howard,

That's a very interesting report, especially as I have a DD (not sure which variant) lying around which I intend to play with one day soon.

They're very quirky sets, and I like the unique styling which has a quite "modern retro" look to it - a DD wouldn't exactly stick out like a sore thumb if it were displayed with some of today's radios.

BTW, have you read the interesting article about these by the late Geoffrey Dixon-Nutall in a back issue of the BVWS Bulletin (on the CD)? I can recommend it highly.

Personally, I would re-spray the front, but only if you could do it to a very high standard (which I'm sure you could). An amateurish DIY paint job always looks worse than a battered original one.

Nick.
Hello Nick,

There are several Double Decca variants, including this 1946 model, the 1947 model which lost the '46' on the front but is essentially the same set, and the Double Decca ML which has a different dial and no shortwave.

These sets do look remarkably modern and the cases were well designed, shame more care wasn't taken in the chassis design though.

I shall look up that Geoffrey Dixon-Nutall artcle and if Ive got it I'll read it.

Thats one vote 'for' a repaint then.

And here is its box.

Howard
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Old 9th Oct 2007, 10:13 pm   #8
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

Nice sets, the Double Decca's. Easy to get going, and has already been stated, very 'modern' in a way. The thing with spray painting is that it can so easily be done wrong. Only do this if you have to.

Was there a mains version too?

Cheers,

Steve P
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Old 9th Oct 2007, 10:17 pm   #9
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

Hi Howard,

Another nice job on the DD. You really must slow down and leave some sets for the rest of us to have a go at!

I have a mains/battery '47 DD in blue and as the front panel wasn't bad I left it as is. I did however, re-spray the speaker grille in a cream (or ivory) as it had rust spots on it. If the front panel had been in the same condition as yours I'd have re-sprayed it. As it's an aluminium panel and it can be completely removed from the radio it's not a difficult job. The 'fresh' grill on mine really made a difference and I suspect a 'fresh' front panel on yours would too.

I'll try to find a couple of 'before & after' pictures to illustrate the point.

That's two votes for a re-paint!
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Old 10th Oct 2007, 12:27 am   #10
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

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Originally Posted by Steve_P View Post
Was there a mains version too?
Cheers,
Steve P
The DD46 only came as a mains/battery effort. This model had one handy feature in that it could charge its accumulator whilst running off the mains.
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Old 10th Oct 2007, 1:24 am   #11
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

A Double Decca made a prominent guest appearance in the 1950 film 'Chance of a Lifetime', written and directed by Bernard Miles, and starring Basil Radford, Niall MacGinnis, Bernard Miles, Julien Mitchell, Kenneth More, Geoffrey Keen, Josephine Wilson, and John Harvey, with minor parts played by Patrick Troughton and Hattie Jacques.

In the film, the radio held a prominent position on the desk of the works manager (played by John Harvey).

Perhaps it was the same radio that appeared in the later film 'Murder at the gallop'!
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Old 10th Oct 2007, 7:38 am   #12
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

I'd respray it, Howard. Such a nice little set deserves it!
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Old 10th Oct 2007, 9:58 am   #13
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

In partial reply to rrdmpb's question re the Philco A3782 shunt resistors, here is the partial schematic:
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The resistor values are:
R11 - 150R
R13 - 180R
R16 - 330R

The valves are:
V1 - DK92
V2 - DF91
V3 - DAF91
V4 - DL94

Most well-designed battery portables with series filaments (typified by a 7.5 volt LT battery) and directly heated cathodes feature a similar shunt arrangement. This was necessary due to the filament current being augmented by the cathode current not only of the valve in question but all its predecessors in the series chain. If uncorrected, this could cause the filament of the last valve in the chain to be significantly overrun leading to a much shortened life, particularly in the case of 25mA, '96 series valves.
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Old 10th Oct 2007, 12:31 pm   #14
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

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Originally Posted by igranic View Post
In partial reply to rrdmpb's question re the Philco A3782 shunt resistors, here is the partial schematic:
Hello again Edward

Thanks for that information, much appreciated.
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Old 10th Oct 2007, 1:27 pm   #15
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

I've always wanted to see one of those sets up close. Thanks for the restoration story and pics.
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Old 10th Oct 2007, 2:09 pm   #16
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

The back of my DD is a pale cream colour and looks as though it's been sprayed. What colour is the DD back panel normally?
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Old 10th Oct 2007, 2:36 pm   #17
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

Reflecting on my previous post, I realised that there was something wrong with the diagram inasmuch as there is no shunt shown for the V3 filament. So I retrieved my official Philco service sheet and, sure enough, the Trader sheet appears to be in error. Here is the filament shunt arrangement as shown on the official Philco sheet.
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Old 10th Oct 2007, 4:04 pm   #18
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

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Originally Posted by Colin View Post
The back of my DD is a pale cream colour and looks as though it's been sprayed. What colour is the DD back panel normally?
Hello Colin

I can't speak for every set of course, but I can tell you that of the two I own my dark blue set has a cream coloured back like yours. Whilst my other 'Double', which has the same case as in Howard's first photo, has a dark almost black back panel!
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Old 10th Oct 2007, 4:06 pm   #19
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

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Originally Posted by igranic View Post
Here is the filament shunt arrangement as shown on the official Philco sheet.
Thanks again Edward for the further information.
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Old 10th Oct 2007, 4:27 pm   #20
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Default Re: 1946 Double Decca 46 MW/LW/SW mains/battery 4 valve portable

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Hello Colin

I can't speak for every set of course, but I can tell you that of the two I own my dark blue set has a cream coloured back like yours. Whilst my other 'Double', which has the same case as in Howard's first photo, has a dark almost black back panel!
Thanks Robert, I wondered if it was as it should be. I suppose it is and it's a match for the cream coloured front.

rgds
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