Introduced in February 1949 in as far as I've found in ivory or green colour. This type of design has more recently been described as the 'toaster design' for obvious reasons. Mine was quite expensive to buy 2nd hand, presumably because of it's collect ability, and it was the ivory colour with some scratches and dead.
The repair
The first thing I attended to was the cabinet, it was just a little boring in white so I ordered a tin of lime green spay paint, removed the Marconi badge and added a black backgroud with a small felt tip pen (cream before) and touched-up the scratches with Tipex, although I later found that to be a mistake as it showed through the first coat of paint. On reflection an off white water colour may have been better. I had to order another tin of spay paint and still struggled to cover the Tipex, resulting in some runs in the paint. When dry I removed the runs using a sharp edge of a razor blade, this helps you to not disturb the surrounding paint.(slice then scrape)
Next came the gold speaker cloth, the rear one is held by 3 x prss studs that look like rivets, but pull away, the frond just slides in as groove. I swilled that under the tap with some soap and a tooth brush, making sure that the edges didn't fray, it was much better, but I may latter fit some new gold cloth.
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| rear and front speaker grilles. |
The chassis incidentally is held in place by 4 self holding bolts and pulling way the 3 knobs.
I removed the mains dropper first, held by a long central bolt and 5 thermal sleeved wires that I un-bolted and marked with a felt tip pen 1-5 with dots on the sleeves. All winding were faulty, the wire had mostly just fell away, but I managed to restore the 50 ohm across the dial light and I ordered a 20 watt 1K ohm and a 5 watt 80 & 50 ohms. I tried to fit them in the small space around the china dropper.
The 820 ohm was replaced with a 1k and I added to missing 50 ohm to the next section, making it now 100 ohm, the 80 I achieved with 2 x 39 ohms in series.
I fitted the 25 watt, 1K ohm to the bolt hole on original dropper, taking care to insulate all wires with heat resisting fiber sleeve. I took a while to judge where it wouldn't be in the way of the loudspeaker and other internal parts, that's why it's best to remove and fix bridging resistors with care. I did try to rewind the original resistive wire, but it was too unstable and I gave up.Finding an original 70 year-old dropper was not an option, lol
I then cleaned the pins on all the valves with emery paper and the valve sockets with a small cleaning too added to my hand drill kit. The valves have high heater voltages because they are designed to be in series with each other and the adjustment for varying mains voltage is done withe the shunt mains dropper taps, as shown above. I found the 1/2 rectifier valve heater was open circuit and replaced that with one I found in a house clearance once.
Then I applied the mains and great, she worked again, mains hum was getting louder as time went by so I replaced all the smoothers (bridged) with 400 volt modern minatures, lots of space underneath for them.
A quick squirt of oil to the tuning vain ball bearings and the volume control, the 6.3 v dial light was faulty, so replaced that, I removed the glass tuning display and found the print was turning to dust, so avoided touching that, one wipe would have removed all text, so I just cleaned around the edges. The black background is not a good idea, I may change that to white and add another light on the left side later.
The speaker was loaded with dust, removed with a tooth brush, one of the knobs had lost it's metal insert, so I improvised with a piece of plastic, was tight enough for the volume pot anyway.
A built-in loop aerial helps bring in all the weaker stations on the dial, and non were found missing even longwave was very sensitive bringing in Paris in the evening. The one magic thing about valve radios is the lack of background noise between stations, just dead quiet. This is due to valves having a very good signal to noise ratio compared the the hissing transistor. I may do some more work on this when I feel the need, until then it looks lovely on my shelf and I'm a happy bunny.
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