Well, it sure sounds like the capacitor problem. I had an X-700 which did that and I have a parts XG-M which did the same thing. It's not a really mysterious problem and is fairly common. There was a chap on eBay only a few months ago who sold the capacitors and full instructions for a very inexpensive price. I searched all over and cannot find him.
I did, however, find the capacitors listed at Micro-Tools here: Micro Tools . I also found this web-page which describes the problem: X-700 . There is also a pdf copy of the X-370 manual floating about somewhere out there.
Hope that this helps.