With the resistor missing, if you look inside the valve you may see G1 glowing white or red - this is a bad thing. As Ian said, a resistor must be present and must not exceed 500k.

So I guess a 470K will be the choice. I shall go and purchase some today.

There are several ways a tube can be destroyed in service; Leaking coupling caps sending the Grid bias positive and another the Plate going open.

On many older sets, where they had not got the message and addressed it. If you left the speaker plug out and the Screen was left alive, or the transformer went open, that meant that the Screen became the Plate. The screen was never designed to handle plate current.

A missing grid connection, or it becomes positive makes it a diode. You can use a triode as a rectifier and an example appears in a Lyric70 series where a #26 triode is used to supply the grid of a #50 -84V with a plate voltage of 450V. In this configuration the grid is tied to the plate.

I've never run this without the speaker attached. I've never worked on valve gear, when it rarely came in the old technicians would get excited and work on them, especially the service manager. Since adding that resistor and replacing a few one meg resistors it now works continuously and reliably. The tone control is disconnected as was found but I'm not worrying about it and I tried to get the magic eye working but I think I'll leave that one as well as I've already seen for how much they sell for. Thanks again for all of your direction in working out the problem. Oh and I had already replaced all the caps. I'm now running it on the bench until a new cartridge for the record player arrives because the one in it is completely stuffed. and I need to completely rewire the cabinet as it has lights that come on when you open doors etc.

In many magic eyes within the cap is a normally a 1Meg resistor. Those resistors have an attrition rate and it is rare to find a good one. The magic eye takes its control voltage from the AGC. It is therefore critical that all of the agc resistors are good.

To ensure that the AGC voltage is optimum it is recommended by most manufacturers that once you have interfered with and changed parts in, that you re-align the IF. That does require equipment and advice if you have never done it,

The comment was a general warning, as I do resort to commercial fixing, it is amazing as to what I have seen over the decades.

There were two 1M resistors behind the magic eye socket and another under the main chassis which was high as well but it made no difference. I decided not to go further as I have read they are of bad design and don't last well. As I already said before I'm not going to spend the sort of money that is being asked for them.

Wow I didn't realise the EM4 was so expensive now. A quick look at ebay showed $150 for used or over $200 new. Then add shipping etc.

Apparently it can be replaced by a Russian 6E5C for much cheaper, but you need a different base.

If the EM4 glows brightly then the problem is elsewhere, but if the glow is dim or nothing, then the tube is most likely worn out. Most of the old-style magic eyes only had a short life.