I have sent photos of the original documents I found in the back of the cabinet.

Great!

Can supply the 1030 circuit if needed.

Thanks - doesn't answer the aerial connection question, but still very interesting to see.

Re 6T5 & 6G5 on eBay:

went for about A$169, US$154

http://www.ebay.com.au/...400547131903.

My 6T5 glows but only very dimly, and you can only really see it in the dark.

What's the likely cause of that? I presume it should glow brightly enough to be seen at night.

Problems in the circuit could be the cause, eg anything that limits current through the valve, but more likely it is just burned out through use. The phosphor used evidently wasn't of good quality by modern standards. A burned out target has dark shadows where the green glow occurs. Also the cathode that emits the electrons that cause the phosphor target to glow deteriorates with use like any valve and limits the current.

I also have one of these that barely glows but works OK otherwise. The cheaper 6U5 or 6G5 are plug in substitutes.

A lot of sites on the web about indicator or magic eye tubes. A few are
http://www.magiceyetubes.com
http://www.radiomuseum.org/forum/history_of_tuning_indicators_meters_graphs_magic_eye_led.html
http://www.radioremembered.org/tuneye.htm

There are no shadows. It's just dim, so maybe it is a voltage problem? What would be the likely cause of a low voltage?

Are ther 6U5 or 6G5 straight swaps, or are there any modifications required? Will the magic eye look completely different, and will I be ruining the authenticity of the set if I put one of those in?

Having a look at my dim 6T5, it is a uniform dark grey except near the centre where there is a thin annulus of lighter grey. The target of an unworn valve is a uniform light grey.

Looking at the circuit, the target is connected directly to the high tension, so the voltage should be 250 - 280DC. The things that might reduce this voltage and hence the current through the target would be poor connections in the valve base or socket or very leaky high tension filter caps. The current through the target should be about 4mA.

Considering the low volume overall that you are getting, leaky caps are a possibility, but would have to be pretty bad. How long had the radio been out of service before you turned it on? If it is a long time the filter caps will be leaky. This could fix itself with time as they reform, but it is possible that it won't and they will remain leaky. In the worst case heat could build up to an extent that they could explode.

To check this out requires a meter and experience with high voltage DC - contact could kill. Do you have any electronics training/experience? Note the warning at the bottom of the page!

The 6U5 & 6G5 are direct swaps - no mods needed - I have a 6G5 in my 830 to conserve the 6T5. The indication of 6U5/6G5 is a varying arc, whereas the 6T5 is a varying annulus, so it will look different. Have a look at the links above for patterns.

Will it ruin the authenticity? Only for those in the know and who are purist restorers. After all, replacement caps and resistors would not be of the period. I would only put the 6T5 in if the radio was on show to enthusiasts. At home for listening to the cricket a 6G5 will do.

A radio for general use in the home must have other modifications eg to cord anchorage and internal earthing connection that would not be original. If you have little kids about (or other gerfingerpoken of any age) you might want to put a back on it.