Does anyone have a manual for a nelco n-250-b zigzag sewing machine?

Sorry free I could not find free manual. Paid version is available at this link
Nelco Sierra 234F manual sewing machine instructions Enlarged Hard Copy - Sewing Manuals & Instruction (bonanza.com)

turn the ZigZag width dial (23) to Zero

https://www.etsy.com/listing/764828308/samb-2-nalco-necci-dressmaker-penncrest

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In my experience, Nelco manuals are sometimes difficult to find. You might try:

http://www.sewusa.com/Sewing_Machine_Manuals/Nelco_Sewing_Machines.htm

Nelco manual Sewing Machines

nelco sewing pdf 1 Docs Engine com

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Owner's manual is the best source.

Nelco Sewing Machine Manuals Instruction and Repair Manuals

http://www.sewusa.com/Sewing_Machine_Manuals/Nelco_Sewing_Machines.htm

Nelco Sewing Machine Manual PDF and CD


P.S.--for ~$35, a standalone bobbin winder can be purchased at JoAnn's Hancocks, or Amazon.com.

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To find a user's manual, search the internet for:
Manufacturer + Model + the word "Manual"

Search YouTube videos for threading tutorials:

Nelco Zigzag Sewing Machine Final Test Demonstration Video

VINTAGE ALL METAL NELCO MODEL 400 2 SEWING MACHINE

NIFTYTHRIFTYGIRL Vintage Nelco model 250 sewing machine

With your Nelco, be sure that you install the needle properly. Frequently, Nelco machines take the needle with the flat side facing toward the throat of the machine--not toward the read like most other machines. The upper thread will thread through the needle's eye from the left toward the right. They also are a left needle position machine--meaning, the standard position of the needle when sewing straight stitch is at the left side of the presser foot, not center like most other machines.

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Reset the sew pattern from zig zag to straight