This might be a bit involved but here goes:
I have an Edison HA-1 15 Clone. Nice looking machine but it's got problems.
I found the first clue in a bunch of bent and broken needles in the case.
I found:
The feed dogs out of adjustment, the were too far forward and impacting on the needle plate.
The presser foot was adjusted too high
The needle bar was adjusted too low
The needle bar and presser foot was hitting each other.
I adjusted the feed dogs, the presser foot shaft and needle bar using the info in the 15-91 service manual I was referred to. (The 15-91 books are not as close to the clones as I'd want them. There are many differences. )
However now it thread jams horribly. So I checked the hook to needle timing as best as I can and find the hook a bit advanced of the needle. Instead of being centered at the needle at the eye, it's maybe an 1/8" past it.
There is another potential problem I'll be checking on later today, but in the mean time, any body have any suggestions from hands on experience, or links to service manuals other than the Singer manuals????
Joe