If it is Sony from the 1980's or 1990's, and there are those small aluminium can Sony made ( no manufacturers marking on them, but Sony always dogfooded unless not practicable, then always use another Japanese manufacturer for the parts they could not make), with voltages under 25V, do not even bother testing them, simply do a blanket remove and replace on them if you want to have the equipment work again.
Sony had a few "service kits" for the electronic consumer and professional AV equipment that they made which were comprised of a pinch roller, a belt or two, a rubber idler tyre ( not the whole idler, just the rubber tyre), a plastic oil slinger for the capstan shaft, a small circlip for said shaft, a call for oil for said shaft and other points ( using a special Sony Branded Oil in a small Sony Branded bottle), a small set of instruction sheets, and then 200 SMD capacitors to replace all on the assorted boards. These would be supplied to the Authorised Agents and Repair Centres for in warranty repairs, and there would be a 20 hour or so labour charge for installing all those capacitors.
If your kit made it out of warranty then that kit was really expensive to have installed, but for the Pro market they had either the choice of fit the kit, and have the unit running like it was brand new again, or scrap it and buy another new one if still in production. I have had a few of those bills over the years.