Welcome to a fools errand. When I worked at Circuit City Service around 2000, we saw a TON of these with capacitor failure. We'd just heat them up and sniff for that typical fishy odor and give the customer a totally unrealistic estimate. NO TECH wanted to mess with these, as results simply could not be guaranteed. So we quoted whole board prices, IF available. These damn caps were a BLIGHT in those years.
The first to fail are always in the DC-DC converter. But it's already over 20 years later, so it's likely ALL of them, especially if you hope to get a clean transfer out of it. It's very unlikely it'll make a clean picture or even have sound. Maybe analog, but most recorded in PCM.
I wouldn't bother. I'd buy a running 8mm DECK. FAR easier to service enough to do what you need. I did this, and used my PC to digitize.
Another POSSIBLE and common problem was the mode switch. Try cleaning it. Maybe YOU will be the only lucky person on earth that has a simple fix.
I'd grab a running deck, do the transfer, and then sell the deck. For all you know the tapes you have could already be un-playable. I have been in the transfer business. Most people wait far too long before they remember to back up their "precious memories".... by then it's usually the media is bad or no running machines. Usually BOTH.
Good luck!