The crackling is just tubes. If the transformer itself is physically humming that is probably DC offset and will go away with a clean power source (no DC offset). Dry room temp storage not only does no damage, its the on/off temperature cycles that cause the most wear so storage is better than daily use as far as that goes.
I buy to get good sound, never to get a good deal. So you just have to ask enough questions to decide if it will be worth living with even if the hum remains.
I buy to get good sound, never to get a good deal. So you just have to ask enough questions to decide if it will be worth living with even if the hum remains.