Hi,
in one SMPS I found blown resistor with the following color code:
Yellow (4)
Violet (7)
Gold (???)
Gold
Black.
Can not figure out the value
Dimensions of the resistor are as standard MF0207 metal film.
I guess that it is fusible resistor, placed in series with primary of the ferrite transformer, on the other side of primary is TinySwitch TNY268.
WTF is resistor in primary?
Thanks Brian, That's what I suspected.
But, to your knowledge, is there any "calculator" for this kind of marking? I have no problems with ordinary 4/5/6 band resistors, (memorised color values 40+ years ago )
It seems to follow the standard 'two digits plus multiplier' sequence (4, 7, * 0.1) with the second gold band being 5% tolerance. The final band might mean fusible or hi-stability, there are inconsistencies between manufacturers. 4.7 Ohms would seem the right kind of value to use as an inrush limiter/fuse in your application.
To you first band may look green, photo was taken under LED "natural white" light, but, you know, white LEDs do not have full color spectrum. It is YELLOW , trust me.
Anyway, thanks for pointing to a calculator, some youngsters might find it useful.