[Arran]

I've never bothered using one on an old AM only radio mostly because if there is ripple, distortion, or any other problem, 90% of the time drifted resistors and bad capacitors are to blame, and maybe a tube problem another 5% of the time, the rest is more obscure stuff like bad mica caps and open coils. So I try powering a set up on a variac, if it looks safe to do so, and then see what it does if anything, then I start changing any old capacitors or drifted resistors I find, I also check the various coils for continuity. If the set doesn't work after the rebuild then I start troubleshooting, checking voltages and so forth. I don't doubt that an oscilloscope can be useful on a stubborn set, but I end up using a capacitor checker and variac much more on these old beasts. I've never gone out of my way to acquire an old scope where I actually had to pay money for it. But if you work on old TV sets and FM radios an oscilloscope is pretty well a necessity for alignment.
Regards
Arran