T2* inductor, LCD interchange?

[vlyne]

My latest acquisition, a T23 motherboard and base (2647-4MU), has a missing inductor at the top and a detached one on the underside. I don't have any spare T23 boards and was wondering if the missing one at the top can be replaced with one from a T20 or T21 board donor? The missing one is between the Savage chip and the Southbridge? chip. Also, can I use a T20/21 LCD (XGA resolution) and LCD cable on a T23 of the same resolution?
Cheers

[vlyne]

OK, I've found out that the bottom inductors are coded "2R5 N23" which I'm guessing is 2.5microH (for 2R5) but I' m unsure about N23 - quality code? amps rating?...?? The only picture I could find of the top is the one that Ray has put on his website but the resolution is not good enough for me to make out the markings except to conclude that it is not the same as the bottom ones. Can anyone please let me know what the markings are and whether the inductors are about the same size as the ones on the bottom. Better still if someone wants to sell me one, or a dead board, please PM.
Cheers

[rkawakami]

Sorry, I must have missed your OP...

Don't have any T20 or T21 patients opened up at the moment but assuming that the parts are the same between them and a T23, the inductor between the Savage and Intel 82801 chips has a code of "150 N28". Due to its proximity to the ADP3806 LiIon Battery Charger chip, I'd say it would have something to do with keep your battery charged.

The ones on the bottom of my dead board (the one pictured in my "maps"), have "2R5" and "5R2" codes, which if I remember right, are 2.5 and 5.2 uH as you have guessed. That would make your "missing" one, 15.0uH then? The Analog Devices datasheet for the ADP3806 references a value of 22uH for a typical application. These three inductors are the same size.

I don't know positively that you can swap out an XGA T20/T21 panel and cable and use them in a T23. The HMM calls out two different ribbon cables between the T20/T21 and the T22/T23 for the 14.1" XGA panel. I have swapped SXGA+ panels between a T21 and T23 without any problems (same cables in both systems).

Hope this helps!

edit: Did a little more digging... Mouser.com has what I believe to be the part you are looking for:

http://www.mouser.com/catalog/630/797.pdf

At the top of the page, the CDEP134 is what is located next to the CPU. The two on the bottom and your missing one on top, are the CDRH104R parts. The CDRH104RNP-150MC is a 15uH.

[vlyne]

Many thanks for the detailed and very helpful information Ray! At least I know what I'm looking for now. As you suggest, the top inductor is most likely filtering power for the battery.

Pity about the different XGA cables. But, before I go out in search for a cable I might just see what the physical differences are between the T23 video socket and the T20/21 cable/LCD. I didn't think there was that much difference between the T20/21 and T23 XGA LCDs?

Thanks for the Mouser link - great catalog (if you know what you're looking for!)
Cheers

[vlyne]

My enthusiasm has been brought down to earth by the shipping charges from the US to down under: cheapest is $US36 via Fedex. I've ended up ordering from a local company (www.farnell.com.au) instead but the closest I could get to the 15uH inductor was a 22uH one (about the same amp rating and shielded) which I'm hoping will be the right size.
Cheers

[rkawakami]

Would that be the Tyco 3631B220ML part? Looking at the datasheet, Tyco does apparently make 15.0uH inductors, although au.farnell.com does not appear to stock it.

The lead physical dimensions look close enough (pad spacing 7.7mm for the Sumida part vs. 8.1mm for the 3631B Tyco part). Height appears to be different (4mm vs. 6mm); the 3631A Tyco part would fit better since it's only 5mm high, but again, farnell does not appear to have it. Electrically, I don't know what the increased inductance will do to the charging circuit. Could give more or less current than normal (analog circuit design not my area of expertise).

[vlyne]

Yes, that's the part I ordered. It's not quite right but the best I could find under the circumstances. It'll have to do. As for the difference to the circuit, the damping frequency would change but since it's proportional to the inverse square root of inductance it should be tolerable? The "inertia" of the circuit would be increased so it wouldn't be as responsive to higher frequency noise/spikes but the capacitor should take care of the remnants. The average current flow should be the same? Time to put theory to the test...
Cheers