Identify smd inductor

[looxuser]

Hi gang, think ive found a defective inductor on a circuit im troubleshooting, checked the usual sources digikey etc but cannot identify this one. it has markings 008. Yy or possibly 008. Yh printed on the top. please help? here's an image inductor is across the top left of centre left of cap.

 

[Kabelsalat]

Hi. I'm kind of interrested in how you concluded with a defect inductor. Internal failure of inductors is very rare - it is more common that the driver circuit that feeds the inductor is the cause of failure.

About 008 (sure it isn't 800 top down?) that probably means that the inductance should be 80nH (if I remember this correct)

 

[davenn]

Hi. I'm kind of interrested in how you concluded with a defect inductor. Internal failure of inductors is very rare - it is more common that the driver circuit that feeds the inductor is the cause of failure.

with this I am in complete agreement

 

[looxuser]

thanks guys here is the circuit diagram. The schorttky diode d7 is a dead short in either direction and the inductor T1 smells burnt with no continuity through the coil ends i can test compared with another. I did accidentally reverse polarity in the power supply, could that have been the root cause?

 

[kellys_eye]

D7 is the reverse polarity protection diode and T1 a simple filter - it should be conductive twixt in and out. The FET in the middle is a switch - via PWRON - and the IC at the top is the converter for the main 5V supply..,

Reversing polarity shouldn't (in theory) have blown the diode.

 

[looxuser]

STRUGGLING TO FIND A REPLACEMENT INDUCTOR ANYONE KNOW THE BRAND, COULD YY BE THE BRAND MARKING YY?

 

[looxuser]

Suppose i could just bypass that inductor for the purposes of proving its dead?

 

[kellys_eye]

That particular inductor looks, to me, to be part of a small SMPS converter circuit - shorting it will destroy the controller. Remove it. It's likely to have only a few turns so you can unwind it and, if you find some similar wire, rewind it (same number of turns).

 

[looxuser]

thanks kellys_eye for the advice yes I was coming to thank conclusion myself but its to tiny to do anything with and the Shelac coating seems to have melted and fused all the turn together, Worth a go though nothing to loose.

 

[kellys_eye]

If the inductor has shorted it's likely that the driver device has gone short too - plan to change that as a well.

 

[looxuser]

hi by driver device you men the mosfet switched by those two transistors? now this choke is in two pieces theres a ferrite post on a ferrite base. there must be two coil of course so looking at the base the coil is embedded in the construction, no continuity through it so theres no hope of re wiring it. here's a picture of the choke cap under microscope if this is as we think 80nH? Now i can find some mouser digikey etc with "100" printed on the top could these surfice?. Now my learning here is that there are straight through chokes 2 pin and what i have 4 pin and they look very similar i.e. its a choke transformer and finding those is far more difficult

 

[looxuser]

So what i've learnt today the number represents the value in micro Henry uH, the first two numbers are the value and the last the multiplier. So this is a 80micro Henry which is shown on a keyboard as yH or uH. DOes anyone concurr please? seems this has to be 800 not 008 as eight would be the multiplier so the units must be upside down as that is showing micro as a "y" and "h" as henry.

 

[kellys_eye]

I take back what I said about it being part of an SMPS circuit......

It appears that you've applied reverse power at some time and the positive line has - somehow - found a way back to ground via T1 and burned the winding.

Given that the inductors presence isn't 100% essential you could simply short out the two coil paths and leave it at that. It'd get the circuit working again assuming there are no other issues.

Hand winding the part isn't beyond 'impossible' if you can't find a replacement but I'd be all...... meh, short it out...... over it.