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I need to replace the inductor on the picture, but the color code is pretty weird: yellow, violet, green, silver (47 * ?? μH +/-10%). According to inductor color codes https://cdn.instructables.com/FRQ/J6VA/H4VQNQFK/FRQJ6VAH4VQNQFK.LARGE.gif , the third position should contain only black, brown, red, orange, yellow.

Can you please help me what this coloring could mean?

Edit: it is a control unit of a garden whirlpool (mspa oasis b-120 sapphire lite)

enter image description here

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  • \$\begingroup\$ Hmmm, looks a bit small for 4.7 Henry. \$\endgroup\$ – Brian Drummond May 7 '18 at 19:19
  • \$\begingroup\$ Whatever else you do, replace C1. The top is bulging - it has gone bad and must be replaced. Compare to C2 there beside it. The top of C2 is nice and flat. \$\endgroup\$ – JRE May 8 '18 at 3:40
  • \$\begingroup\$ @JRE yes I'm aware of that, but thanks :) \$\endgroup\$ – amik May 8 '18 at 8:04
  • \$\begingroup\$ Any relation to this Amik? \$\endgroup\$ – JRE May 8 '18 at 10:36
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Just by looking at it's physical size, it is probably 4.7 µH. If that is true, then the base unit would be pH. I guess that's what the manufacturer picked for this inductor series.

However, before you replace the inductor, re-solder the top joint. That's clearly a bad solder joint, at least on this side of the board. It may have been marginal all along, then finally went open. If so, you don't need a new inductor.

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  • \$\begingroup\$ It could be mH as well. They come in that size, too. \$\endgroup\$ – Hearth May 7 '18 at 21:36
  • \$\begingroup\$ @Felt: That's possible, but still quite a stretch. If that little thing is 4.7 mH, then it would have to be very low current with quite high series resistance. \$\endgroup\$ – Olin Lathrop May 7 '18 at 21:37
  • \$\begingroup\$ True enough. That's just closer to the standard μH scale, was my thinking. Incidentally, you mention the bad solder joint, which made me notice that the capacitor at the top of the image seems to be bulging a little, though the image quality makes it hard to tell. That could be a concern for the asker, too. \$\endgroup\$ – Hearth May 7 '18 at 21:41
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If the colour bands were interpreted as per the standard IEC 60062 markings which many manufacturers use (though not actually strictly applicable to inductors as it turns out), it would be a 4.7H inductor 10% tolerance:

Yellow = 4
Violet = 7
Green = x100000
Silver = 10%
(in uH)

However, as noted that seems ridiculously large for the size (then again you don't give any reference of scale in your photo).

To throw a curve ball, that may not be a yellow marking at all, but rather a Gold band, in which case it may not in fact be 47...H at all, but rather:

Gold = 0.
Violet = 7
Green = 5
Silver = 10%
(in uH)

Which equates to 0.75uH. (Reference: Vishay Inductor Color Chart, VMN-MS6576). That would be much more reasonable for the size.


Short of purely guessing that the manufacturer used some non-standard basis such as pH as the other answer does and guessing at the value, I would simply remove it and measure as @Felthry suggests.

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    \$\begingroup\$ I have trouble believing that something that small is 4.7H. \$\endgroup\$ – Hearth May 7 '18 at 20:05
  • \$\begingroup\$ @Felthry hence apparently. I can't find any other info beyond standard inductor codes. \$\endgroup\$ – Tom Carpenter May 7 '18 at 20:08
  • \$\begingroup\$ I must agree that it cannot be 4.7H - this is few milimeters stuff, by eu.mouser.com/Passive-Components/Inductors-Chokes-Coils/… inductors about 5H are few inches large. \$\endgroup\$ – amik May 7 '18 at 20:10
  • \$\begingroup\$ I wonder if it's using nH as a base unit instead of μH? That would be nonstandard, but it would result in a 4.7mH inductor, which you could definitely find in that size. \$\endgroup\$ – Hearth May 7 '18 at 20:12
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    \$\begingroup\$ Sorry, but -1. There is absolutely positively no way that is a 4.7 H inductor. \$\endgroup\$ – Olin Lathrop May 7 '18 at 20:27

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