Electronics > Beginners

Schematics information - what does NF mean?

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bitman:
On the attached schematics from a Raspberry Pi 3, the R56 is missing on my Pi - as it's a voltage divider I'm going to look to replace it.  But I'm not sure what the NF means on the diagram?  If the "F" is "film" what does the N stand for?  I know of Carbon and Metal film - none seem to match.  On the other hand, since R56 is 0Ohm I really wonder if I'm on the right track - I've never seen a voltage divider where one of the resistors is 0 - what's the point?

capt bullshot:
Guess it's an unknown variant of "no load", "do not populate", ...

Wait a sec, my guess would be "not fitted"

ruffy91:
NF means it's not populated and 0 Ohm to Vout means no scaling (so 0.6 to 1.39372V programmable Vout)

Nusa:
What they said - not fitted. It's a solder selection mechanism, which could be a voltage divider, but in this case is not. In that context, 0 ohms makes sense.

If you look for those pads on the actual hardware, it should be obvious.

bitman:
It's "funny" - I remember reading a few threads on 'missing components' but it never occurred to me that this was that case. See the image of the missing resistor - it looks like solder is on the pads, which is why I thought things were missing. I would expect to see the straight copper if it was just skipped.  So I guess it's about solder selection as you stated - unfortunately I'm not sure what that really entails. All I can say is that this is the first time I look at this relatively old RPi (it stopped working) and I see a pretty bad solder job - and I swear that's left over paste on R57.

But at least it makes sense now. Thanks.

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