Hi! I have a Seiko compound feed (STH-8BLD-3). I’ve been using it for about one year making backpacks (not leather).
The problem - At low speed, the machine intermittently makes a low pitched rattle/groan. I cannot hear the sound when I turn the machine by hand (with or without the belt on the pulley). The sound goes away as soon as I speed the machine up.
Here is a short video with sound. https://imgur.com/a/XNju9LX
The sound really comes through in the video. It’s not quite that bad in person, but it’s bad enough that I don’t want to use the machine until I fix it.
Background - I tuned it when I got it and lubricate it regularly. I don’t recall when it started making this sound. Maybe it happened gradually.
I lubed it the first time I heard it, and it didn’t help. I’ve now removed all the covers, checked everything for loose parts, removed the hand wheel and remounted it, removed the needle position sensor, etc. I swapped the servo motor with another machine and replaced the belt. Nothing helped. The machine still sews very well.
It seems like the sound is coming from the middle of the machine, in the enclosed area to the left of the upper oil reservoir. But it is hard to know. I tried a mechanics stethoscope, but the noise is so loud that I can’t pinpoint anything.
There are no sewing machine mechanics in my area except one shop with a really long waitlist, so I learned to fix all of my machines. But I’ve spent a couple nights on this and I’m stumped. I’d really appreciate any suggestions.
Thank you!
Phil