Dim Trace
Hi all and thanks for the feedback and suggestions. Yes, the trace is at full intensity (as per the intensity knob). There is a secondary focus and intensity control (or primary, depending on which way you look at it) on the board in the form of trimpots - the focus alters things but the intensity seems to do nothing to the trace. It has been a long time since I had it apart now, even though it is still sitting cluttering up my workbench, so my memory is now dimming as to the exact symptoms and what I did and didn't try. I remember going through a bunch of stuff with Goodwill techs (they went above and beyond actually) and in the end they gave up and said it was likely a dead tube, but it is so bright in very slow traces that I just can't accept that diagnosis, and the fact it starts bright at any given setting and fades over about 30 seconds to a minute to nothing indicates to me something wrong in the sweep/drive circuitry.
As it stands, I have run out of talent and even though the scope is what I would call analogue - that is, it isn't all surface mount this and digital that, but solid old recognisable op-amps and transistors the likes of which I have in my parts bins. I have already located and replaced a few dead trannies and diodes which got it to light up in the first instance, so I was pretty pleased with myself in that regard, though now I have pulled and tested every component in that area or part of the system, including all resistors and caps in the vain hope I found another dead component and it was magically fixed. Alas, this didn't happen and the danger now is the board's traces are very fragile with age (and my ham-fisted soldering/desoldering) and as a consequence I have had to repair many lifting and broken tracks and pads.
I have learnt an incredible amount from doing this so nothing has been a waste of time. To be honest, I would have chucked it long ago except for the fact my uncle went to a lot of trouble to ship it over to me from Australia and I thought it at least worth having a go at fixing as I believe they are a reasonably good scope at the time. I don't have the motivation to buy some new digital whizz-bang thing that would be wasted on my analogue/audio-level hobby anyway so it would have been ideal but there we go. One day I'll dig back into it and have another shot at the title - who knows, I might just get lucky.
Cheers and have a great Xmas and New Year for those who celebrate such things.
Thanks again and I'll report back anything I discover.