[Tim]

Hi

Same "dotted" trace, but starts very bright. Brightness control inoperative, but can be turned down slightly after a few minutes.Focusing not very good either.

Started with a few voltage measurements:

Voltage on collector of TR904 with x-y and brightness up full 31 volts(should be around 25. This voltage DOES change with adjustment of the brightness control.
Grid and cathode voltage of CRT are low(or is it high?) at about -650 to -700 volts, as opposed to the quoted -1.6KV. measured on the 2500 volts range of an AVO8. The manual actually specifies " a 20,000 ohms / volt meter capable of measuring up to 2500 volts". Sounds like an AVO 8 to me!
Grid Voltage remains unchanged with CRT base unplugged. The trouble is I don't know whether that's a fault, or whether the voltage is actually OK, being loaded down by the meter and the fault is elsewhere.
I do have another meter(A GEC Select test) which has the same resistance as the AVO8 on 2500 volts(50 meg ohms),
I suppose I could try both meters in series to get 100 meg, and then they would each display half the voltage. If the total is different then my first readings must have been loaded by the meter.
The trace is very bright, and calibration seems fairly good( in vertical direction anyway) so I think the anode(9KV) is OK

I haven't had a chance to get a 'scope on it yet, but I'll have a poke about and see what waveforms are present.