So, I have in front of me a 1974ish Sound City valve amplifier. To my certain knowledge it hasn't been powered up for ten years, and maybe quite a lot longer. No real idea of provenance or whether it was operational when last used. Take it apart, vacuum out all the dust, look for obvious failed components sure, but what other precautions should be taken with something this old that hasn't been used for so long? Are there any tests that are advisable for an amateur equipped with just a multimeter before electricity is allowed anywhere near it?