Brett,
It all depends on type of glue. Most old radios used water based hide glue, even on the plywood layers. I've used a steam iron and brute force successfully, but the steam machine Terry mentioned (if you have/can afford one)may allow you to confine the steam to a smaller area, while prying/pulling on just those parts being separated. Dents can also be removed from veneer with water and iron, but all finish must be removed deep down into the dent. Apply water to the dent only and let it soak in a few seconds, then apply an iron (dry/no steam) over alum foil at the dent. As best I know, water soaks into the cell structure of the wood, then applying a hot iron causes steam pressure within the wood pushing the dent back to its original shape. May take several attempts to remove moderately deep dents. I always block sand after every attempt to assure only the barest amount of wood veneer is removed. You'll have to use your best judgement, because raising dents with too many applications of water and iron can actually swell the veneer and its softwood backing to a point that you'll be sanding away the veneer, reaching the underlying softwood.
marv
:I have a wood cabinet radio that has loose and separated joints that need to be reglued. What do I use to soften the old glue in the joints so I can get them apart, cleaned and ready for regluing, but is safe for the plywood?