Working on fifty year old Singers is comfortable, many of our mothers used such machines. They are familiar. Some sewing machine mechanics are so use to these older machines, they shy away from more modern machines. They are content servicing mechanics they have seen before.
That is great for the hobbyist, but not so good from the professional.
Sewing machine use has changed big time. When I was a boy growing up on the farm, Mom had one of those old Singers. She used it often for clothing repairs (4 boys and a girl) and holiday projects. Sewing machines were part of almost every home. It seemed a necessity. People used them for practical necessities.
Today, however, some may have a closet machine just to have one, but most sewing is done for the sheer joy of sewing, quilting, embellishments, embroidery, crafting, etc. Fun is the focus. Self expression rules.
High end sewing machines are all the rage among those who love sewing. Fancy 1,000 stitch combo sewing and embroidery machines are status symbols for sewers. Even multi-needle embroidery machines are common.
These high end machines can be understandably intimidating for the technician. They do not look like your mothers old Singer. They do not sound like it either.
If you examine the actual workings of the multi-needle machine, you discover it is much more simple than first glance. It is basically a single-stitch sewing machine (no feed dogs), with a robotic arm that move the fabric. With this in mind, if you know how to service and adjust a regular sewing machine, you already know most of what you need to know to service this one. Set the needle bar assembly one needle bar at a time exactly same. Then set the hook assembly.
The robotic are may look complicated, but it is just two "rubber bands" mounted to form an X and Y axis. The computer does the rest.
Take courage, stretch a little, and discover how you can service multi-needle embroidery machines.