Repairs for Grundig Satellit 500 and 700

[ibramr]

Greetings. I would appreciate your advice of a reliable repair facility in the US for Grundig Satellit 500 and 700. The 500 is dead, and the 700 works for few minutes, then goes into a coma. I like both radios, and would like to continue using them for some more years to come (if possible). Thank you very much.