May 9, 2017

Necchi BU - NA Wiring

After a lengthy search I discovered that there were no simple wiring diagrams for the BU series.

Since the light is one of those 12v things from my 1972 Fiat Spider it requires the transformer to drop the 110v to 12v

Here are photos of both the Nora and the Miranda.


I removed the auxiliary cord from both

The light is chassis grounded so there is only one wire going to it


Schematic

Based on the two machines I have for reference, use only if you have background and / or familiarity with electrical systems.

I removed the auxiliary outlet on both because the cord was deteriorated.



8 comments:

  1. Tom, thank you for this info. I was looking for the same info for 2 parts machines that need rewiring. This helps greatly.

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    1. Glad it helped, I'm not an amateur but I found this wiring confusing, and after blowing a hole in one of those 12v lamps I decided trial and error was not going to be fruitful

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  2. I understood the stepdown transformer, but didn't realize the "light" switch as actually an on/off switch, but makes sense. Since mine were also with mismatched motors, I was wondering if the transformer was enough to vary speed as I'm used to a motor with a different brush offset for a separate speed. Seems like the transformer is not an ideal way to vary motor speed. My early BU Nova didn't have that option. Many thanks, again.

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    1. Yes I think that using a transformer to step down the top speed may be the cheapest and therefore the least desirable way they could have gone. A servo with a real variac would be nice. They didn't have cheap electronics back then!

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  3. Thanks for this post.
    I'm working on a supernova that has some trouble with the transformer, and it looks very similar to what you have in your machine. Do you know the voltage and amperage values the transformer should put out?

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    1. Interesting question, I will have to open up one of my machines and take some readings, may be a week or two.
      There certainly are no markings that I have seen and from what I have noticed the Hi - Low speed diff is very minimal I wonder if hooking it up direct (eliminating the Low altogether) would be an option

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  4. Thank you SO much for making this wiring diagram! I was just given my grandmother's Nora and someone had cut the wires off at some point, probably 40 years ago, so I was a bit confused as to how to install the new wiring.

    Do you happen to know where to get the fly wheel belt by any chance? I'm in Arizona so mine is dry rotted.

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    1. Glad to be of service.
      The belts are common start with the assortment pack at Joann's ; anything that fits and doesn't slip is a belt, nothing special.

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