Probably the filter caps have dried out. This is a fairly common problem. The metal can caps have 3 ground lugs and one positive terminal and Tek used the can as a jumper on the PCB. You can replace them with 105C snap caps and use an adapter board to match up the footprints between the cap and the PCB. You can find them on ebay and there are images/gerbers floating around the net. You need reasonably good technique to desolder the old caps without delaminating the traces from the pcb, but it is not too horrible.
Another issue that it might be is one of the bridge rectifiers failed.
Since it obviously need repair, I wouldn't offer more than $40-50, but that depends on where you are.
If you get the scope, check the ripple and voltages of all the low voltage power suppllies, that will point out the issue.
It's a nice scope; Tek sold zillions. As many people will likely point out ad nauseam, it's not a DSO, but it is still useful along the lines of a one eyed man in the country of the blind and all that. I have one and use it from time to time.