I searched and only saw Service Manuals as you stated. Not sure what information you need.

I saw several youtube videos that might give you contacts to email for assistance. I also saw what appear to be the same model for sale on ebay so you might also try emailing vendors as well.

Example: https://www.youtube.com/watch?v=iUv1Y5e9cl0

When it comes to vintage equipment, manuals are hard to find as paper gets trashed and the companies that are no longer in business don't have web sites - not sure how you could get documents that you want without luck. That seems to be a model that is still being used from the web discussions I saw, so maybe consider posting or contacting blogs that have it mentioned.

FIXYA is a free service where answers are provided for free by users just like you, so if you have success with your question or know the answer to someone else's, please post it.

Regards.