Contact this fellow. He apparently worked for HeathKit (Standard made some radios for them) and had worked as an authorized repair center for Standard before they left the market. He evidently bought out Standard's parts inventory when they left. According to those that have used his services, he does good,work with a rapid turn-around.
The info is about 4 years old, so I hope it's still current. I don't know of any other repair facilities that specifically work on Standard Amateur equipment. I have 2 H-T's and a mobile, and all are still functioning well after 15 years or so. (The H-T batteries are a bit aenemic, though.)
Good luck. I hope Matt can help.
Matt Adrian KD8ZB
SAR Technical Services
1792 Nash Drive
St. Joseph, MI 49085