A Ruby Red Eraser will take the corrosion off with no damage. Providing there is still some metal to the runs. Then you can re-tin the runs with fresh solder. Or, dump it, you may fight gremlins a long time.....
They are (most likely) not wrong from the factory. Phase Linear and MANY other MFGR's don't bother to go back and waste time and money to fix all the skizmo's so go with what's on the boards. Especially if they are unmolested from the factory. Sansui was the worst.
Safe and Operational is the key. Good Luck. I'd never want to risk a good builder rep on 50 year old pile of iron. They USUALLY don't last...... Usually.
The original was seen around the 4th of July smoking behind the Burger Boy in Vancouver. I never thought he'd last that long salting the fries for the last 27 years.
HEY, That's false advertisement. I was heading to the kitchen to make a peanut butter and fried naner samich and then I saw............ WRONG ELVIS!!! Dammit..... :)