T41 and singing capacitors when charging

[doktorkoo]

my T41 makes high freq singing when charging. It is not heard if I remove the battery, so it must be one of the charger components...

Any ideas about the component values in that section, so I could start changing them one by one?

[rkawakami]

I don't have one of my open T41 chassis available at the moment but I believe that most of the charging circuitry is near the battery terminals on the top side of the motherboard. You should see an inductor in the area and also an ADP3806(?). The inductor is possibly what is singing. If the T4x systems use that same type of charging circuit as the T23, then the inductor will look like what is in the center of area G6 of this photo:

http://www.rkawakami.net/ibm_t2x/mobo_top_72_legend.jpg

The inductor is the black ceramic square with a round circle on top and the ADP is the 24 pin IC located nearby. That IC on the T23 motherboard is in between G5 and G6. You can try swapping out the inductor. If it's like the T23, then it's made by Sumida and the part number is something like CDRH104-150. The '150' represents the inductance value; 150uH.

[doktorkoo]

You should see an inductor in the area and also an ADP3806(?). The inductor is possibly what is singing. If the T4x systems use that same type of charging circuit as the T23, then the inductor will look like what is in the center of area G6 of this photo:

Thanks for the advice. Unfortunately there is no "wired" inductor close to the ADP3806 in T41, at least on the top side of the PWB. I haven't detached the motherboard yet....