Thanks for reply’s.
The controller is a TNC 150.
There is ‘burnin’ on the screen. You can see figures on the screen with the machine turned off.
As stated above, a guy said to me that the screen was ‘gone’. At collection a guy that had worked in the place said the screen was failing for years but was still usable.
I removed the monitor from the controller to have a look at the CRT.
The CRT is a Philips M31_340 LM/ED . These CRT’s have high resolution and were recommended for data display and ‘high end’ computers back in the day. It is a green screen I think. The LM/ED is the phosphor colour and glass tint (or no tint) and are not electrical parameters (not important unless you are particular).
There are other tubes that will substitute I believe but it is very hard to get data or info on them.
The Orion 310GNB31 seems to be a contender. It is available fairly cheap on ebay. About 50 quid second hand from monitors from an Amstrad GT-65. The resolution may be lower.
Also commodore pet 4032 but they are too expensive and hard to come by.
I may not need a monitor. You can purchase replacements but they range from 500 to 1000 quid.
There is a second hand M31-340 Philips monitor available on EBAY from the USA for about 300 quid + postage (an arm and a leg on top of the price!).
Anyhow on opening up the monitor I discovered that the heater of the CRT was not connected up as shown in the photos. I believe the yellow wire (going to pin 1) should be going to pin 4. Pins 3 and 4 are for the CRT heater connection. Pin 1 needs no connection (so long as pin 5 has a connection) as it is common to pin 5 . This info. I took from a Philips tube publication namely “Philips Monochrome tubes and deflection units T16” ,page 242. It is available on the web.
The last dude that was servicing the machine must have made a mistake and put the yellow wire to pin 1 instead of pin 4. The soldering on pin 1 is poor though the photo does not show it clearly. I connected up a 12v supply to pins 3 and 4 and the heater lights up OK as per the photo. It draws about 130mA (as per the publication above).
There is absolutely no way the tube would work without power going to the Cathode heater.
Still have not gotton around to pluging in the machine.

Will fire up generator soon.
Thanks all.
Tom