Honest answer: it depends on why you want it, and both answers are legitimate.
If the goal is a working bench scope: buy modern. A current two-channel 100 MHz digital scope is inexpensive by any historical standard (entry units from the major brands sit in the few-hundred-dollar range), and 100 MHz is generous for audio and enough for CD servo work. Restoring a dead scope to save money does not survive that comparison.
If the goal is the restoration itself: a vintage scope is a legitimately good project. The boards are serviceable, documentation for the classics is out there, and you learn more bringing one up than watching one run. There is no shame in the "because it is there" motive on this forum.
Either way, the safety gate is the same and it is non-negotiable:
- Test the transformer before the first power-up. Insulation resistance is the tell: above 10 megohms the insulation is good; 1 to 10 megohms is marginal and will misbehave under load or humidity; below 1 megohm means compromised, do not power it up at all.
- Bring it up gently. A variac for controlled bring-up and a dim bulb tester for current limiting are the two cheapest insurance policies on any bench.
- Isolation where it matters. An isolation transformer is safety equipment on transformerless gear and breaks ground loops in the test setup.
One more thing: the old test gear that stays useful even now is mostly the passive stuff. Variacs, isolation transformers, dummy loads, and bench supplies do not become obsolete the way displays do. If you inherited a pile, those are usually the keepers.
What did you find, and what is the model? Scope threads here get good fast.