All I needed now was an oscilloscope. This came up locally and it was functioning. Shipping can be a major expense for scopes because of their size and the requirement to package well. Local is better. And the gentleman I bought it from introduced me to the world of vintage antique radio which has involved joining clubs going to museums etc etc. Serendipity.
The Tektronix 900 series is, I think, the 'Rodney Dangerfield' of Tek scopes. But at the right price they are a good little scope certainly good for audio and vintage and useful also at low HF. They are easy to work on. No special components. Not built like a 'real' Tek; but then not much is. The square shape can be easier to fit on the bench. The 935 does 30Mhz and has delayed sweep.
However. Being vintage means never being quite so trouble free as a new Rigol. After using the 935 for a bit it started being 'flaky' and jittery and channel 2 didn't like to trigger. Being an orphan so to speak there's not nearly so much hangin out there on the web (as other Tek scopes). But Tektronix manuals are almost textbooks! Buy the Manual! The 900 series is available on CD and also if you're like me you can with patience get a real printed manual.
These are very easy to take apart. The boards are interlocked with 'edge' connectors and one of the main faults is intermittant power through the power supply board on the rear side. After tweaking that connector most of the jitter went away. The vertical attenuators both had to be cleaned finally with copious Simple Green, alcohol, water rinse, repeat sequence. Then following the lead of an online reference to a diode that failed and affected the triggering replaced that and everything works. Also polished scratches out of the plastic screen cover with Novus polish.
Replacing the astigatism potentiometer. Googled the part number and got the oem part! You can see how wide open the board is. Generally speaking these are very very easy to work on.