Welcome to QB. Generally, one should clean and oil the machine. Frequently, the vintage machines have been sitting for a while and are stiff and sluggish from the old oil drying up.
A free download manual for the 403 from singer.com can be found at
https://res.cloudinary.com/singer-se...ng_Machine.pdf
Since this machine is considered in the same series as the 401 There Is a good thread about the 401 at
She's real fun, my 401... Pay particular attention to
She's real fun, my 401... as it would apply to your machine as well. There is a good page about the 401 at
https://archaicarcane.com/stuck-in-t...lant-o-matics/ that may help with the 403 also.
There is a service manual at
https://sewingdude.wordpress.com/201...ervice-manual/ however, I would suggest not jumping to conclusions that you need the service manual.
Janey - Neat people never make the exciting discoveries I do.
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