Page 3


As previously mentioned, this set has received some 'previous attention'. Here's an example of the standard of work... the central resistor has been tacked on to an extension wire with a dry joint. The right hand radial capacitor, which looks to be under some physical stress, does not appear on the original circuit. This has been hitched between the anode and cathode of the line output valve, maybe for picture linearity reasons? It is only rated at 200v...Yuk! The anode resistor at bottom left is 22k not 23 ohms. I have only just started. What else will I find?

I shall have to go through the entire circuit, component by component, checking for mistakes, and sort everything out.

The first thing is to make up a selection of original looking capacitors. Here they are, all concealing new capacitors within. Their appearance has been based as closely as possible as those fitted originally in the 1930s. How it used to look has been gleaned from some photos kindly sent me by Mike Barker, who is currently re-winding the EHT transformer.

It is possible the large brown re-constructed 'Hunts' unit shown, situated at the rear top of the chassis, should in fact have a silver finish. I am awaiting some more photos from another collector to resolve this, and if necessary the colour will then be changed.

After several more days, I've finished replacing all the capacitors under the main deck with the more authentic looking versions. The picture shows just one area of the under-chassis. The large block condenser is now also mounted above chassis and connected up.

The very early Emiscope 3/3 cathode ray tube uses its own special plug-in base. The set arrived with the rather nicely made substitute that had been specially made, shown on the left. However, this was not only non-original but also tended to slip off!

Thanks to the help of Cobaltblue on the Vintage Radio Restoration discussion board I was able to find the correct, original base - seen to the right and now wired in. This rare part was donated for free and is a typical example of the unstinting generosity and help to be found on that board. Without this kind of support, it would be much, much harder to do my job.

Note the diagram between the two items. This shows the base connections to the tube. Interestingly, this shows only one 'blank' connection at the top, whereas there are actually two, on both the tube and the base. This means it is 7-pin, not a 6-pin connector...

 With the main work on the main chassis finished, it's time to look at the finishing touches. Here are the valve screening cans. They need re-plating...

So after preparation, into the plating bath they go. Nickel will be carried from the positive anode plates to the negative screening cans, connected as cathodes. The process is slow and will take many hours.


The valves - only some of them shown here - are all physically spruced up and then go on the valve tester. The customer also provided some spare valves. All were tested, and the best examples have been added to the set.

Going in now is the rather special ceramic-based X41C frequency changer valve for the television section. Note the socket too is of ceramic construction. At the outlandishly high frequency of 45 MHz (in 1938), special measures like this were needed to ensure good performance.

The valves are all plugged in. The line output valve inside the black perforated screening can on the right is a KT44 with an anode cap; not the KT41 (without cap) as specified in the manual. Since the KT44 provides considerably beefed up performance, we might surmise this set is a later model - from 1939...

This is how the backing card of the radio dial looks like while it's being "re-flocked". The task is to create a new felt-look surface.

First, the work is coated with a special adhesive that binds the flock powder to it. With new flock, it is sometimes possible to squirt it through the nozzle of the flock container straight onto the work. However once the stock of flock gets old, it tends to stick to itself in clumps (as is the case here) and the only realistic option is to pour it on and tap it down lightly with the fingers. Several hours after this picture was taken the surplus flock was shaken and blown off, leaving a tidy-looking flocked surface.

The only flock I have in stock is of a tan colour so the card was later sprayed in matt black, using several light coats to avoid clogging the flocked surface.


Here's an original identifying label found attached to the tube neck. It's very important to preserve little historical details like this. A needle and magnifier was used to tease apart the tiny knot on the other side...

When such paper labels are grubby, they can often be cleaned up using the 'cheesy' type of rubber. This is a dry - and therefore safe method.

I'm curious about the condition of this tube and whether it can be improved... Previously it had been reported as giving a very dim picture.

So it goes on the tester.


As expected, to start with the emission reads almost zero. However, after a little judicious "rejuvenation" I was able to improve it to a steady reading at the level shown. Tubes with this amount of emission can, in my experience, display quite good pictures.

The plan therefore will be to first try this tube, as it is now, in the restored set. Then the customer can decide whether it's worthwhile to send it off to France for a rebuild. Another factor to consider will be the condition of the screen, which undoubtedly will have an ion burn.

It remains just possible I may have saved the customer around £700 as a result of this little exercise...

Back to the radio dial now. In the end I wasn't satisfied with the result of flocking it... it lacked a little "je ne sais quoi"... so I decided on another approach. I bonded a piece of black felt to the original card and added masking tape over all the edges to ensure the felt would then cut cleanly around the edges.

This is the result. For this shot it's not been lined up perfectly with the dial (that goes on top) but you get the general idea. I'm now happy with this.

It's now time to take a look at the power supply chassis. Here it is, cleaned up, but still looking a bit messy...

One of the transformers - the EHT transformer - is missing. It's currently with Mike Barker for rewinding. He reports good progress.

The isolation between the mains transformer input winding and chassis has been megger-tested and proves to be excellent.

The unit is now tidied up under-chassis as well.


The recently added EHT smoothing capacitors are replaced with something more in keeping with period of the originals, although there was in fact one combined unit fitted when this set was new.

These two capacitors actually were supplied by the customer. They megger okay and measure correct for capacitance, though the only real test will be try them for real. Just in case... I shall protect the new EHT transformer, when it arrives, with additional fusing.

The voltage that will later be found on the tops of these capacitors will be absolutely lethal. I've added rubber caps, but these represent only token protection.

The story continues... click here...

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