Hi Ann,
There were two types of 910 produced. The Mark I has the battery and the Mark II is a modified version that does not. It feeds off the mains power and has a built in memory. If it is a Mark I, the battery will be under a small cover on the top left of the machine, under the word 'Brother'. Don't force this open because the modified version looks identical but cannot be opened.
If your husband opened the cover and there was no battery on the left, then you have a Mark II. As for the patterning not working, there is a small 'eye' that reads the mylar sheets that sometimes clogs with dirt, texta and gunk. If you remove the cover, on the right where the pattern is inserted, you will see a small device at the front that moves right and back, reading the sheet. Very carefully..... move a soft cloth over the reader to clean it.
I don't know about the capacitor, but make sure that you feed the mylar sheet to the indicated line before turning the machine on. Does the green light come on?
Can you punch in the positioning numbers into the console? What does the machine do?
Good luck with the testing.
Rose M, January 2011