Hi, I'm having trouble finding a repair manual for the singer 400 series. In particular the 478 model. I'm told this machine has "trouble" with thread tensioning but have been unable to get more specific info as yet from the lady in question. A user manual would also be appreciated as I'm a little unsure how to thread it to test for myself. I would also be interested in the value of the "ohmic resistance range" of the foot pedal. Thank you for any help you are able to provide!

Hi
strange as it may seem, there are free White overlocker/serger manuals via the Singer website. The manuals include 19th century models too!

Look under Singer's "Support and Resouces" then select "Instruction manuals" , or follow this link: http://www.singerco.com/support/instruction-manuals

On the Instructions Manual page you'll see it says "Find Your Manual - Step 1, Step 2 etc etc" and under that there's a search box that says "Model Number"

Into this search box just type "w"
(don't type "white", because that doesn't work)

You'll be taken to a near incomprehensible results page,
A) if you have a 20th century model, try doing a find via Ctrl-F and enter in your machine's model number.

B) if you have a 19th century machine, unfortunately the method to finding the manual you need is a case of clicking and opening the PDFs.
However may I suggest a couple that may be of use:
"W7treadle"
- this is a manual of White treadle with a "boat" style bobbin shuttle
"WRotary"
- this is a manual of White treadle with a "rotary" style bobbin shuttle

Good luck, and I hope you find what you need :)
Kind regards
Kura

Instruction Manuals