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If you go on Vinylnet, you'll be able to find the manual for a 1500 and it'll tell you if it has a switchable power supply. Your headshell and cart will be fine as long as the headshell is straight for an non straight arm.
I'd definitely ask to see a photo of the bottom, and to see a demonstration of it in action and that the suspension is working. They're getting on for 50 years old.
Are you sure it's not a switchable power supply?
https://www.ebay.co.uk/itm/311954997435