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Power off and then wait a minute or so, and then unplug. Shouldn't be much of a charge there to worry about.
The low volume issue could be any number of things. It might be bad caps or resistors in the Automatic Volume Control Circuit. Maybe a soft audio output tube.
Depending on your electronics interest/knowledge you might look for a local repairman. There are usually clubs, and often times they will do repairs or help you out.