Flexoman, it's probably a capacitor. I'm not familiar with that radio , but it's a common problem in vintage radios. There are kits for sale.
Edit : read that you have help. They should do all of the larger caps although you might get away with replacing just the one that's bad.Replacing all of them is a shotgun approach usually successful, instead of spending time looking for the bad one . In situ bad caps can read good on a multimeter anyway.
Likely one of the larger values in the power supply as Josh stated or audio, ( they either fail uf or short-short not good!)
If that's what it is, that's a symptom they will go bad one by one ( like an old car unless you do the whole thing)
Do all of them while the chassis is out if they don't mind , my advicehttp://hamamateuradio.com/realistic-dx150a-replacement-electrolytic-capacitor
If you want to try it yourself
You don't really need a schematic or service manual. Remove one and replace with the same value, then do the same on the next one and etc. Note the arrows or lead makings on the body, they need to be positioned the same way as the old . New/ old should be marked with the values so that's not a problem.
Not rocket science but skills with soldering will help. The real challenge is be careful,don't rush and try not to overhandle or butcher
I have wanted one of those or later models for awhile, but unfortunately I am under a radio restriction decree from the wife and am monitored for any new acquisitions. If I got one it couldn't be out in the open anyway.